The unofficial LARE Blog!

Warts on a wall wart

2012-02-03T11:31:00.001+05:30

This is what happens when you plug in a AC/DC adapter meant for mains input of 110VAC/60Hz (USA/Japan) into a 230VAC/50Hz (India). AC/DC adapter is a simple Stepdown Transformer > Bridge Rectifier > Capacitor type. You can see from the pictures that the windings on the primary side heated up and melted and shorted out. The heat also caused some insulation to melt and ooze out of the transformer.

It seems the wall wart (colloquial for AC/DC Adapters) has grown warts of its own! Hemorrhoids even!!

Pulse Width Modulation

2012-01-21T15:18:00.003+05:30

Here is a video of a PWM signals generated using a microcontroller. The two signals are in quadrature phase - i.e. their phase difference is 1/4 of their period (or you can say they are 90 degrees apart). The signals were generated using an ATmega32. Program was written in Assembly Language. AVRStudio4 and STK500 were used as development tools.

Maruti Swift VXI OBD2 Connector

2011-10-23T19:28:00.002+05:30

We have a Maruti Swift VXI which has a K series engine. Here's a photo of the OBDII connector located on the left inside of the dashboard panel under the steering wheel.

Do not yet know what all one can do with it.

Ubuntu upgrade caused blank screen on my Acer Laptop

2011-09-25T21:43:00.000+05:30

I have an Acer Aspire 4736 Laptop running ubuntu 10.10. I recently used update manager to upgrade to 11.04.

After upgrading and rebooting, I had a problem with the following symptoms:

Acer's BIOS Splash screen showed up followed by GRUB OS selection menu.
After that the laptop's screen turned purple and then blank.
A few seconds later I could hear the welcome sound but the laptop screen was blank.
I connected an external monitor via HDMI and the image came up on the external monitor

And so I scoured the net and came across this forum thread and realise that my laptop's LCD panel was showing an image alright but the backlight was off - confirmed this by squinting closely at my laptop's LCD panel.

I followed unknown47's advice and restarted and it worked. If you have an Acer Aspire laptop and have a similar problem, do this:

Bootup ubuntu.
Connect external monitor.
Edit /etc/rc.local and add before exit 0:
setpci -s 00:02.0 F4.B=00
Edit /etc/default/grub and change
GRUB_CMDLINE_LINUX_DEFAULT = "quiet splash"
to
GRUB_CMDLINE_LINUX_DEFAULT = "quiet splash acpi_osi = Linux"
Execute the command sudo update-grub2
And restart your computer.

Getting Tata Photon+ to work on Ubuntu

2011-09-25T14:53:00.017+05:30

So, finally got this working!!!

What I have:

Machine: Acer Aspire 4736
Operating System: ubuntu 10.10 Maverick Meerkat
Device: Tata Indicom Photon+ VME101 HSIA USB Modem (Manufactured by Olive vendorid:productid = 201e:2009)

And I wanted to get it to run on Linux, so here's the sequence of steps I followed.

Do not plug in the modem.
Open "Terminal" from "Applications>Accessories".
Type the command cd /etc/usb_modeswitch.d and press enter.
Type sudo gedit and press enter.
Enter your ubuntu password when asked and press enter.
When the text editor opens up, copy paste the following into it.
#######################################################
# Haier CE 100

DefaultVendor= 0x201e
DefaultProduct= 0x2009

TargetClass= 0xff

MessageContent="5553424312345678000000000000061e000000000000000000000000000000"
MessageContent2="5553424312345679000000000000061b000000020000000000000000000000"

NeedResponse=1

CheckSuccess=10
Save the file as "201e:2009" (Yes that's the filename - a pair of 4 digit hexadecimal numbers seperated by colon).
Close the text editor.
In the terminal window, type the command sudo gedit /lib/udev/rules.d/40-usb_modeswitch.rules and press enter.
Enter your ubuntu password when/if asked.
Text editor will open the file "40-usb_modeswitch.rules".
Browse to the end of the file till you reach the last line which says LABEL="modeswitch_rules_end"
Insert a few lines by pressing enter before this last line.
Insert a new entry (just like the other entries in the file above) by copying and pasting the following:
# Tata Indicom Photon+ VME101 Olive Mobile Broadband Modem
ATTRS{idVendor}=="201e", ATTRS{idProduct}=="2009", RUN+="usb_modeswitch '%b/%k'"
Save the file.
Close the text editor.
Restart your computer.
Plug in your modem.
Wait for 15 seconds.
Right click the network icon next to the clock and select "Edit Connections".
Navigate to the "Mobile Broadband" tab.
Click "Add Connection". Your Modem will be listed there as "Qualcomm CDMA Technologies MSM".
Press "Forward".
Select country as "India".
Select provider as "Tata Indicom (Photon+)" and press forward.
Click "Apply".
In the yet open "Network Connections" window, select "Tata Indicom (Photon+)" and click the "Edit" button.
In the "Username" field, type "internet".
In the "Password" field, type "internet".
Click "Apply".
Close the "Network Connections" window.
Left click the network icon next to the clock and from the menu that appears, select "Tata Indicom (Photon+)".
Wait for your computer to connect to the internet and then start browsing away to glory. To disconnect, repeat step 32.
Next time, you will just have to plug in your modem, wait for a few seconds for the "Tata Indicom (Photon+)" show up when you left click the network icon next to the clock and then click on it to connect again.

References:

Notes:

The Tata Photon+ modem has a ZeroCD feature which allows the device to act as a CDROM drive containing its own drivers and application installation files. This CDROM mode is the default mode when the device is plugged in to your USB. To use the device as a modem, we need to force it to switch modem - a task which is achieved on Microsoft Windows by the drivers which are installed from the virtual CDROM drive. On Ubuntu, editing the "40-usb_modeswitch.rules" in steps 9 thru 15 above helps automate the task of the forcing the Tata Photon+ USB device to switch from mass storage mode (acting as a CDROM drive) to modem mode. If "40-usb_modeswitch.rules" is not edited, one would have to execute the command sudo usb_modeswitch -c /etc/usb_modeswitch.d/201e\:2009 everytime the Tata Photon+ device is plugged in.
Step 17 - restarting your computer: may not be necessary, but it doesn't hurt anyway.
Step 19 - It takes a few seconds for the modem to boot up and for the computer to force it to change modes and be recognised by the Network Manager as a modem.
Tata Photon+ distributed many different versions of it USB Modem devices. The above post is only applicable for the ones marked "V-ME101"

Motorola S-record file

2011-09-04T18:34:00.005+05:30

Compilers for microcontrollers from Renesas Electronics like R8C and M16C usually output a .mot file which is a Motorola S-record file. This is a standard ASCII text file which contains the opcodes to be placed at each location within the target microcontroller's program flash memory. A programmer application software would read this .mot file and program the flash memory of the microcontroller chip accordingly. Motorola S-record format is somewhat similar to Intel HEX file format

The following quick reference chart will help you understand the Motorola S-record file format easily - specially useful if you are developing software to parse .mot file. The diagram was based on the data presented at: http://www.amelek.gda.pl/avr/uisp/srecord.htm

A4 Landscape PDF File of the above diagram is here.

Linear Barcodes

2011-09-03T19:56:00.002+05:30

Barcode scanners are fun, got my hand on one of these to catalog my book collection on librarything.com. Its easier to create the collection by scanning off the ISBNs off of books.

The one I use is iBall CS-153 Linear Barcode Scanner

Here is a random list of barcodes I scanned off of various products around my bedroom.

LUSDJ0D165050038A11601

4718235227159

8904149401006

8903539010200

8901124715332

9788184890266

9781408809594

9780595142361

9780007428052

9780743440295

9722121221225

LXPG40C0269290B9161601

92904738216

SA00000183A

4902430281232

355067048902647

HT13XTJ26185

99HMN005-00

4710937348842

205000001519991

W1255ZCZC00072R

884912116505

8901499006653

037000230151

8901491503051

8901491104555

8902080504060

8902570801860

8901138714550

8901424008332

8901396465003

8901030207068

8901023005800

8901396144007

8901396112136

8902570801471

4902430354332

8901396151258

8901571001248

8901012155035

8901393004700

89000816

8901207900839

8901233008011

8901063004023

8901063035034

8901876001035

SLF02A067030004802

8901207503559

8901207503221

6589726583256

884898315176

4800888142238

8901296102121

8901180118023

8901860010517

4711734822603

6932008080019

8906016571058

074470584933

Bar codes can be used to encodes lots of different kinds of data, Universal Product Codes being one of them. http://www.upcdatabase.com is a good source to figure out what each Universal Product Code Stands for:

For example:

9781408809594

This is a Bookland ISBN code, which means it's an ISBN number encoded as an EAN/UCC-13. You can tell this by the first three digits of the EAN/UCC-13 (978). The numbers after that are the ISBN. You'll notice the last digits differ, though -- EAN/UCC-13 and ISBN calculate their check digits differently (in fact, the check 'digit' on an ISBN can be a digit or the letter X).

Here are the innards of iBall CS-153:

The microcontroller is AT91SAM7S64

It seems to be a camera based bar code reader.

Here is the iball Linear Barcode Scanner User Manual and Configuration Leaflet. This barcode scanner does not have any buttons on it and neither is it supplied with any application/device driver software. The bar code scanner emulates a standard USB HID Keyboard. All data read from a bar code is sent to the computer as key presses. The user manual has various bar codes printed in it. To change the settings of the barcode scanner, one has to scan the bar code associated with that configuration change and voila! the new setting will take effect immediately (of course you have to scan bar codes for "start configuration" and "stop configuration" too and you may need to power cycle the device too)

Barcode Scanner from ZXing Team is a nice Android app which uses your cell phone's camera to read barcodes off of products and then fetches their description and price from the internet and displays the data on the screen.

Open Source within Plain Sight

2011-09-03T18:28:00.004+05:30

Now days lots of consumer devices use lots of open source software.
For example Samsung's GT-E1175 GSM Cell phones uses the following open source software:

Independent JPEG Group

Independent JPEG Group is an informal group that writes and distributes a widely used free library for JPEG image compression.

homepage and source code

Newlib

Newlib is a C standard library implementation intended for use on embedded systems. It is a conglomeration of several library parts, all under free software licenses that make them easily usable on embedded products.

wikipedia entry | homepage and source code

Challenge Handshake Authentication Protocol

In computing, the Challenge-Handshake Authentication Protocol (CHAP) authenticates a user or network host to an authenticating entity.

wikipedia entry (theory) | RFC1994 | source code

MD5 Message-Digest Algorithm

The MD5 Message-Digest Algorithm is a widely used cryptographic hash function that produces a 128-bit (16-byte) hash value. Specified in RFC 1321, MD5 has been employed in a wide variety of security applications, and is also commonly used to check data integrity

wikipedia entry | RFC 1321 (includes source code)

GT-E1175 Open Source Announcement Leaflet:

The thing about memset(), memcpy() & memove()

2011-05-26T22:16:00.002+05:30

Came across these two pieces of advice regarding the use of these library functions in C:

DO use memmove() instead of memcpy() in case you're dealing with overlapping memory regions.
DON'T try to use memset() to initialize type int, float, or double arrays to any value other than 0.

More details here. If you are an embedded C programmer, its worth a read.

Installing Android on a Virtual Machine running inside Windows using VirtualBox

2010-12-31T00:09:00.001+05:30

Operating System: Windows 7 Ultimate 64 bit

Download VirtualBox (filename: VirtualBox-4.0.0-69151-Win.exe) from http://www.virtualbox.org/wiki/Downloads
Download a ISO image of Android-x86 built for installation on a virtual machine (filename: froyo-vm-20100812) from http://www.android-x86.org/download
Install Virtualbox.
Download "VM VirtualBox Extension Pack" (filename:Oracle_VM_VirtualBox_Extension_Pack-4.0.0-69151.vbox-extpack) from http://www.virtualbox.org/wiki/Downloads
Install "VM VirtualBox Extension Pack" by double clicking on the file.
Start VirtualBox
Create a new Virtual Machine named "Android-x86-froyo" for OS "Linux" and Version "Linux 2.6" with RAM as 256 MB and dynamically growing IDE (not SCSI) Harddisk of 2 GB Capacity. Enable both the serial ports (COM1 and COM2) but leave them in "Disconnected" mode.
To the above Virtual Machine, attach "froyo-vm-20100812.iso" as CD image to the IDE controller to which the above Harddisk is also attached.
Start the above Virtual Machine and when it boots from the ISO image, select the option "Install Android to harddisk"
When asked to choose partiton, select "Create partition" to enter the cfdisk utility. Within this utility select "New" and create a "Primary" partition of the default selected size (2146 MB).
Select the option to "Write" the partition table.
Set the just created partition to be bootable
Again select the option to "Write" the partition table.
"Quit" the partition utility.
Select the "sda1" partition and press "OK" to install Android to this partition.
When presented with the filesystem options to format sda1, select "ext3".
Select "Yes" when asked about installation of GRUB bootloader.
Select "Run Android-x86" at the end.
For the currently running "Android-x86-froyo" Virtual Machine window select "Disable Mouse Integration" from Machine menu of virtualbox. Once that is done, click within the window so that mouse pointer is captured. This will enable you to click and drag the mouse pointer to unclock the Android homescreen. To release capture of mouse pointer press the "Right Ctrl" key on the keyboard.
To shut down the Virtual Machine send an "ACPI Shutdown Signal" from the Machine menu of Virtualbox then switch to the Virtual Machine screen and select "Power off"

Setting up toolchain for developing applications for Android on a Windows PC

2010-12-25T01:17:00.003+05:30

Operating System: Windows 7 Ultimate 64 bit

Download "Java Platform,Standard Edition JDK" (filename: jdk-6u23-windows-i586.exe) from http://www.oracle.com/technetwork/java/javase/downloads/index.html
When asked to select the platform, select "Windows" and not "Windows x64" because we want the 32 bit software and not the 64 bit one eventhough our OS is 64 bit.
No special installation instruction, just keep clicking next on the installation wizard dialog boxes that pop up.
Download "Eclipse IDE for Java Developers" (filename: eclipse-java-helios-SR1-win32.zip) from http://www.eclipse.org/downloads/
Use the 32 bit Eclipse eventhough your OS is 64 bit.
Extract the folder "eclipse" from within eclipse-java-helios-SR1-win32.zip to C:\
Rename this "eclipse" folder to "eclipseandroid" in case you want to distinguish it from other installations of eclipse.
Run C:\eclipseandroid\eclipse.exe
Rename the workspace path from "C:\Users\Anurag Chugh\workspace" to "C:\Users\Anurag Chugh\androidworkspace" and before pressing "OK" check the box "Use this as the default and do not ask again"
Close Eclipse. Check the box "Always exit without prompt" before pressing "OK"
Download "Android SDK Starter Package" (filename: installer_r08-windows.exe") from http://developer.android.com/sdk/index.html
Install installer_r08-windows.exe. No special installation instruction, just keep clicking next on the installation wizard dialog boxes that pop up. At the end uncheck the box to prevent running the "SDK Manager" before clicking Finish.
Create shortcut to "C:\eclipseandroid\eclipse.exe" on the Desktop and name it "Eclipse - Android"
Download "ADT Plugin for Eclipse" (filename: ADT-8.0.1.zip) from http://developer.android.com/sdk/eclipse-adt.html
Start Eclipse using shortcut placed on the desktop and go to Workbench.
Click on "Help > Install New Software" .
Click "Add"
Click "Archive" and browse to point to "ADT-8.0.1.zip" and install everything related to Android. You will have to accept the license agreement before proceeding.
Restart Eclipse when asked to do so.
Close eclipse.
From "Start Menu", right click "SDK Manager" listed under "Android SDK Tools" and click "Run as Administrator".
Install all packages listed under "Android Repository". Select "Accept all" Radio button. Internet is required for this step. (takes lots of time to complete)
If it throws an error, check the "Force https:// to be http://" checkbox listed under SDK Manager "Settings" and try again
Within SDK Manager, go to Virtual devices and create a new "Android 2.3 - Level 9" Virtual device named "A2.3L9Hello". Set SD card Size to 64 MiB. Close the SDK Manager.
Start Eclipse.
Go to Window>Preferences>Android
Browse for SDK location and make it point to "C:\Program Files (x86)\Android\android-sdk-windows" and click Apply.
Click OK and come out of the preferences.
File>New>Project
Select "Android Project" and click next.
Project name: HelloWorld
Build Target: Android 2.3 (API Level 9)
Application Name: Hello, Android
Package name: com.example.helloandroid
Create Activity: HelloAndroid
Click Finish
Open HelloWorld>src>com.example.helloandroid>HelloAndroid.java

Replace all the code in there with:

package com.example.helloandroid;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class HelloAndroid extends Activity {
   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       TextView tv = new TextView(this);
       tv.setText("Hello, Android");
       setContentView(tv);
   }
}

Press the "Run" button (one with "Play" icon on it)
When asked for a way to run the application select "Android Application"
Whe asked to "Save Changes" click "Yes"
Virtual device will boot up (takes lots of time). First textual animation appears and then Graphical Animation appears.
When the home screen appears, the application will run and display "Hello Android". If it doesn't press the launcher icon on the screen (one with the small square grid on it) and run the "Hello, Android" application by click on its icon.

Explore Further:

http://developer.android.com/resources/tutorials/hello-world.html

50 Hz AC Mains

2010-10-04T00:25:00.002+05:30

So the waveform collection wouldnt be complete without the 50Hz AC Mains. Since the oscilloscope I am currently using is USB powered PC based, it can't handle high voltages such as the 230 Volts AC/Hz available in India.

So I stuck my probes onto the secondary of a AC/DC step down adapter..

..connected the oscilloscope to my laptop and observed the waveform and more specifically, its frequency:

Just to be safe, I operated the laptop on battery and disconnected the laptop charger from the mains.

Next I loaded the AC/DC adapter with a 47 ohms resistor...

.. and observed the signal (note the distortion):

If you are wondering if (and why) the utility frequency ever changes then the following articles would interest you:

10 Mbps Ethernet

2010-10-03T20:00:00.001+05:30

Waveforms of signal on a 10 Mbps Ethernet CAT5 cable (captured differentially on the RX+ and RX- wires):

For the info regarding how I managed to captured this waveform have a look at the usenet discussion here and the supporting info here.

Click on the image below to know how I forced my network card to operate in 10 Mbps mode only:

Dual-Tone Multi-Frequency

2010-10-03T18:35:00.004+05:30

Whenever we press the keys on our touchtone landline phones, it transmits two sine waves simultaneously. The interface at your telephone exchange recognizes the frequencies of both of these waves and hence identifies the key pressed. This is known as Dual-tone multi-frequency signaling. The various combinations of the frequencies of each of the keys are as below:

DTMF Frequencies in Hertz
      
KEY  FREQ1    FREQ2
        
1    697    1209
2    697    1336
3    697    1477
A    697    1633
        
4    770    1209
5    770    1336
6    770    1477
B    770    1633
        
7    852    1209
8    852    1336
9    852    1477
C    852    1633
        
*    941    1209
0    941    1336
#    941    1477
D    941    1633

Here are how the waveform of DTMF signals corresponding to various key presses look like:

Digit 0

Digit 1

Digit 2

Digit 3

Digit 4

Digit 5

Digit 6

Digit 7

Digit 8

Digit 9

Hash (#)

Asterix (*)

And here is what the FFT of DTMF signal for Digit 5 looks like - note the peaks near 770 Hertz and 1336 Hertz:

Here is the 20Hz Ringing Signal which appears on the line to indicate an incoming call:

And finally this is a capture of a waveform during a conversation:

RS485

2010-10-03T17:55:00.002+05:30

Here is a printout of screen capture of A and B signals of an RS485 Bus as captured on an oscilloscope (Agilent 54621A). The RS485 Bus usually consists of a twisted pair cable connected to an RS485 Transceiver. In the case, below, a twisted pair cable has not been used - the signals were directly observed at the A and B pins of DS75176 loaded by a 120 ohm resistor and biased by two 560 ohm resistors. The bus is bein operated in half-duplex mode. DS75176 (which is equivalent to MAX485) was connected to the UART of Atmega8 AVR Microcontroller. The data being transmitted were the characters: 'a' '0' '1' '2' 'K' 'Q' - in that order. The UART frame format is 8-N-1 and the baud rate is 38.4 kbps. The signals A and B were captured on two different channels both referenced to the common system ground.

This waveform was captured while me and my classmates were working on our final year project at the end of our undergraduate engineering course. The reports of this project titled "Multi-Utility Sensor Network" are here.

Spectrogram

2010-10-03T15:21:00.001+05:30

How to observe Spectrograms of various signals or latest pop/techno songs:

Buy a Nokia phone - specially the ones like Nokia 5800 or Nokia X6 or any other which are labelled "comes with music" or "music unlimited"
Install the nokia support software on your computer - especially the Ovi Player
Validate your music coupon and download a few songs from using Ovi Player. This is completely legal.
Install Winamp 2.95 (older version). You can get it from oldversion.com here.
Start Winamp, go to preferences, set the visualization plug-in to "Spectrum Analyzer + Voiceprint" which is present in the "Nullsoft Tiny Fullscreen 2001" Library
Load the song in winamp, play it and press "Ctrl+Shift+K" to watch the live spectrogram of the song. The Spectrogram is updated from left to right. Press "Esc" key to get out of fullscreen mode.
If you want to see the voiceprint of your voice, "add a URL" to playlist and type "linein://" into the textbox asking for location. After this is done, double click on the entry in the playlist which says "Line in" and set the recording control to Microphone, switch back to winamp, press "Ctrl+Shift"K" and speak or whistle into the Microphone to view the spectrogram. Instead of the microphone, you can set the recording control to "Line in" and apply any signal to your sound card's "Line in" and observe its spectrogram. If you are worried about frying your computer's sound chip, try this.

Setting up the preferences for visualisation in Winamp

Spectrogram of a song. The instantaneous spectrom is displayed using the bars at the bottom of the screen. This spectrum is translated to pixels of varying colours depending on the amplitude at the frequency and displayed as a vertical line in the voiceprint (or spectrogram). Within the spectrogram, the frequency increases vertically from bottom to top.

Setting the recording control to microphone for "linein://"

Whistling into the microphone and observing the Spectrogram

Frequency Modulation

2010-10-03T14:43:00.000+05:30

Here's a GIF Animation of the modulating signal (top) and the corresponding frequency modulated signal (bottom) captured on an analog Cathode Ray Oscilloscope.

The modulating signal is a very low frequency sine wave fed from signal generator to an ICL8038 FSK trainer kit. You can see the frequency of the carrier wave change as the voltage level of the modulating signal changes slowly.

The video was shot using a digital camera. The location is VESIT, Mumbai's Communications Laboratory.

Here's how the GIF animation was created on a Windows based PC using free tools:

The video was originally in .MOV (Quicktime) format. It was converted to uncompressed AVI using Rad Tools (free version of QuickTime must be installed on your system before you can convert the MOV to AVI).
The uncompressed AVI was then loaded into VirtualDub and Image Sequence of a selected duration of video was exported. This particular time period of the video consisted of a sequence of 14 frames. The frame sequences were selected such that the waveform in the start frame and the end frame were almost in phase (i.e. looked the same) so that when the 14 images when displayed one after another should give an impression of a continuous loop.
The exported images (or frames) were converted in a batch job from BMP to GIF using IrfanView.
The GIF animation was created using Microsoft GIF Animator.The GIF images were imported into it, the animation was set to loop forever and the delay between each image was set to 3/100 seconds since the video was originally shot at 30 frames per second.
The GIF animation was saved and ulpoaded to Picasa which now supports GIF images with animations.

The above steps can be used to convert any AVI file to GIF Animation. You do not need to used RAD Tools in case your video is not in MOV format as VirtualDub can directly import video files encoded with popular Codecs like MPEG or DivX or XviD. Now days are many websites which help you create a GIF by uploading individual images for each frame. Some of these are:

GIFup (can import images from flickr)

gifninja (allows conversion of video to GIF)

imator

Gickr

Electroluminescent Strips

2010-09-16T16:01:00.000+05:30

Electroluminescent strips are available in all shapes and sizes. They can even be cut to whatever shape is required as long as the end terminals are left unscathed. These strips find use as backlight for watches and other devices having LCDs. High voltage AC signal is required to turn on an EL Display and special drivers are available to achieve this. Typical AC voltages applied to the EL display are 50V to 250 VPK-PK, with a frequency of 50Hz to 1KHz. The current consumption depends on the area of the display - a display having an area of a few (< 5) square inches would draw somewhere around few tens of (< 100) microamperes.
So the job of the driver is to essentially draw a few tens of milliamperes at 3.3/5.0 volts DC and convert it to around 100Vp-p AC at a few hundred hertz and supplying a few tens of microamperes of current.

Information Regarding ELs:

Inside Electret Microphone

2010-09-16T15:24:00.000+05:30

Electret Microphones come in all kind of sizes. Let us look inside three of these:

Type 1

Type 2

Type 3

Few useful links explaining the construstion and use of Electret Microphones:

HyperPhysics
WM-60a , WM-61a microphone modification
SparkFun
Powering Microphones
History
Hosiden
MEMS enables multi-microphone consumer products (Article in EDN, Photo of Electret Microphone Schematic)

These Microphones are available in Mumbai, India from Visha Electronics Corporation

Breakout Boards

2010-09-16T00:34:00.002+05:30

So what do you do if you want to assemble a prototype of a project based on an IC which is only available in Surface Mount Package like one of these?

You make use of an appropriate Breakout Board (BoB). Lets look at some of these:

Quad Flat Package (QFP)| upto 64 Pins | 0.8mm Pitch

Quad Flat Package (QFP)| upto 160 Pins | 0.5mm Pitch

Quad Flat Package (QFP)| upto 160 Pins | 0.65mm Pitch

Shrink Small Outline Package (SSOP)| upto 40 Pins | 0.65mm Pitch

Small Outlined Integrated Circuit (SOIC)| upto 28 Pins | 1.27mm Pitch

All the above breakout boards are available in Mumbai, India from Visha Electronics Corporation

Make sure that before you solder your IC to the breakout board, you do remove the extra tinning from the tracks using a soldering iron and copper desoldering braid as shown in the photo below. Use of soldering paste while doing this is recommended. This will flatten the tracks and the you would be able to easily and accurately position the SMD IC before soldering it.

Eagle design files of a few other breakout boards are also available here.
Please note that breakout boards are not recommended for use with ICs which deal with high frequency signals (i.e. those above a few megahertz)

Inside a Ceramic Filter

2010-09-15T20:41:00.002+05:30

Here are how the insides of a 460 kHz Ceramic Filter look like:

Ceramic Filters (3 pin devices) are not to be confused with Ceramic Resonators (2 pin devices).

Some more info on these from around the internet:

Inside a Ceramic Resonator

2010-09-15T17:21:00.002+05:30

Here are how the insides of a 455 kHz Ceramic Resonator look like:

Ceramic Resonators (2 pin devices) are not to be confused with Ceramic Filters (3 pin devices).
455kHz is used as the Intermediate Frequency in AM Radio Receivers.
Some more info on these from around the internet:

Integrity Technology (App note here lists standard oscillator frequencies.)
Simple RF Oscillator using this
Experiments with Ceramic Resonators
Ceramic Resonator Circuit Symbol (Main Site)
Receiver with Ceramic Resonator

Inside Power Resistor

2010-09-15T16:06:00.004+05:30

What do the insides of a power resistor look like?

Here are photos of 2.2 ohms/5 watt wire wound ceramic resistors. The outer shell is made of ceramic (which is a good conductor of heat but a bad conductor of electricity).

In Mumbai, India, such resistors can be bought from Visha Electronics Corporation

Reed Switches

2010-08-31T17:25:00.008+05:30

Read an FAQ on "reed switches" here and the wikipedia entry here.
Here is what a pack of 1000 pieces of reed switches looks like.

Printed Circuit Boards - Construction Materials

2010-08-27T20:39:00.009+05:30

There is a lot of confusion amongst students and fresh graduates with regards to the PCB fabrication process. I have accumulated some knowledge from around the web (References: Link1 | Link2) and added some of my own here to serve as a ready reckoner of a few important notes regarding PCBs.

PCB Process in Brief:

Copper laminate -> Drill board -> Deposit Copper -> Photolithography -> Tin lead plate or finishing -> Etching -> Hot air level -> Solder mask -> Electrical Testing -> Routing and V-scoring -> Product inspection -> Final cleanning -> Packaging.

PCB Terminology

Base Laminate - That sheet of insulating material (a.k.a. dielectric) to which a thin copper foil is affixed on either or both sides. This material is constructed by repeatedly uniting two or more layers of material together. The process of creating a laminate is lamination, which in common parlance refers to the placing of something between layers of plastic and glueing them with heat and/or pressure, usually with an adhesive. Refer wikipedia entry for Laminates. Base Laminates are of many types (depending on the materials used to make them) - FR2, FR4, CEM1 etc.
Pre-preg - stands for "pre-impregnated". The Base Laminate is made of insulating layers of a particular dielectric typically laminated together with epoxy resin prepreg. A pre-preg is a sheet of material that has been impregnated with a resin cured to an intermediate stage. Read "How's FR4 Made" for a clearer explanation.
Epoxy - Used to bind the various dielectric plies together during the process of lamination. Eead the Wikipedia article for a clearer picture.
PTH or Plated Through Hole - A hole with the plated copper on its sides to provide electrical connections between conductive patterns present on two or more conducting layers of a PCB. There are two types of PTH - one is for mounting leaded components and may or may not create electrical connections between patterns of the two or more conducting layers through which it passes. The other one (called a via) is not used for mounting components and is used only for the purpose of creating electrical connections between patterns (i.e., traces) on two or more conducting copper layers.
Blind via - A via hole that does not pass completely through the printed circuit board. A blind via starts from one side or another.
Buried via - A via connects two or more inner layers but no outer layer, and cannot be seen from either side of the board.
Pad - The portion of the conductive pattern on printed circuits designated for the mounting or attachment of components.
Bare Board - A finished printed circuit board (PCB) that has no components mounted yet.

Base Laminates Types (taken from here with some additions)

FR2 (a.k.a. Paper Phenolic)
The base is composed of multiple plies of paper impregnated with flame retarding phenolic resin. The major advantage of the material is the low cost, good electrical and punching performance. In India, you will find most cheap single sided PCBs made of this material. It is brown in colour. Wikipedia article on FR-2
FR3 (a.k.a. Paper Epoxy)
The same as FR2 but the paper is impregnated with an epoxy resin providing better electrical and mechanical properties. The material is used in TV, computer and telecommunication applications.
CEM1
The material is a composite with paper as the core and woven glass cloth on the outer surfaces - each impregnated with epoxy resin. The material can provide the punching characteristics of the previous materials and many of the electrical and mechanical advantages of FR4 laminate. The surface of this material is white in colour because of the woven glass but brown on the sides because the core is made of paper.
CEM3
This material again has woven glass cloth on both outer surfaces but with non-woven glass in the core. It has epoxy resin and is more suitable for through plated holes than CM1.
FR4 (a.k.a. Glass Epoxy)
By far the most often specified product produced from multiple layers of woven glass cloth impregnated with epoxy resin. It has superior properties to the other laminate sheets with a higher price tag. The glass transition (Tg) temperature of the material is between 125-140°C. This laminate is mainly used for plated through and multilayer functions. It is used in all types of electronic products including military space and advanced computer systems. Wikipedia rticle on FR-4
FR5
Basically the material is the same as FR4 but with a modified epoxy filling which improves the Tg to between 150-165°C. This improves the thermal stability of the product. Generally used where a product is required to work at higher temperature.

Also have a look at the Materials section of Wikipedia entry on PCB.

Copper Thickness

The copper in a PCB is rated in ounces, and represents the thickness of 1 ounce of copper rolled out to an area of 1 square foot. For example a PCB that uses 1 ounce copper has a thickness of 1.4 mils. mil is a unit of measurement of length. 1 mil = 1/1000th of an inch. 1 inch is 2.54 cm. PCBs are available with varying copper thicknesses:

1/2 ounce per square feet > 0.7 mils or 18 microns thick
1 ounce per square feet > 1.4 mils or 36 microns thick
2 ounce per square feet > 2.8 mils or 72 microns thick

Photos

Here is a photo of 3 PCBs of the same design fabricated using three different base laminates. All PCBs are 1.6mm thick and have tracks etched only on a single side. A green colour solder maske is applied to the side on which tracks are etched. The copper thickness is 36 microns but after tinning, the thickness rises to about 70 microns. Tinning is the process of applying a thin layer of Tin to the copper pads whhich stay exposed even after the solder mask is applied. Tinning protects the pads which would have been otherwise oxidised and would prevent solder from sticking to the copper. (Copper gets oxidized when it comes in contact with air, Tin doesn't get oxidised) The dimensions of the PCBs are 160 mm by 103 mm

Top Side (Component Side)

Bottom Side (Solder Side)

Side View

The PCBs featured in the photos are of the same design : "89C51/89C2051 General Purpose PCB" The PCBs and the components in a kit form are available from:

Visha Electronics Corporation

Address: 1st Floor, Kalpana Building, 349 Lamington Road, Opp. Police Station, Mumbai 400 007, INDIA

Phone: +91 22 23862650
+91 22 23862622

Fax: +91 22 23884401

Email: info@vishaworld.com

Prices of the Bare PCB as of August 2010:
FR2 Version - 50 Indian Rupees
CEM1 Version - 70 Indian Rupees
FR4 Version - 90 Indian Rupees

A page describing the assembly and use of this PCB for developing the projects around the 8051 microcontroller is located here.

Links to 3D images of PCB cross-sections found on the web:
Image1 | Image2 | Image3 | Image4 | Image5 | Image6

Also checkout the course website for "Concepts of PCB Design" @ University of Bolton

The Insides!

2010-08-20T17:09:00.008+05:30

What better way to teach students about architecture of embedded systems than to actually open up a few and show it to them?
We opened up a digital camera, an iPod, a GSM Cell phone, a TV game and a few computer accessories. We then stuck their innards between two thick pieces of A4 sized transparent plexiglass each and bolted them together to form exhibits. For the digital camera, we even printed out a pair of transparencies to outline the various sections on the main board. During the workshops, they proved to be a great practical teaching aid for exposing students to some real life design. After a few workshops, the glue gave way and the various sections inside the exhibits started falling apart. Since the sides were open, the dust made matters worse. And because we used to pack all of these 5 exhibits together, the bolts on each of them ended up scratching the surfaces of the plexiglass.
In the second version of these exhibits, we ought to make the transparent box sturdier and dust proof.

The Insides - of Fuji FinePix A345 Digital Camera

The Insides - of Fuji iPod Photo 20GB

The Insides - LG G1800 GSM Cell Phone

The Insides - TV Game (NES Clone)

The Insides - Assorted Computer Accessories

EDN Magazine carries a regular feature called "Prying Eyes" in which they open up a gadget and decribe its internals. The Prying Eyes articles are all available online here.

Restoring P89V51RD2 's Bootloader

2010-08-12T21:17:00.017+05:30

If you have used P89V51RD2 a lot, you would have realised that many times it happens that the microcontroller refuses to be recognized by FlashMagic and then you have to resort to replacing the microcontroller with a new one. Assuming that your hardware circuitry and computer are free from any problems, there are only two things that could have gone wrong - your microcontroller has suffered an internal hadware failure (maybe because of overvoltage or ESD) or the bootloader residing inside the microcontroller has got corrupted. Microcontrollers with spoilt bootloaders can easily be fixed by re-programming the bootloader into their flash memories. So before dunking those seemingly dead micros into the waste baskets, try to resuscitate them by reprogramming their bootloaders. Heres how you can do this using a Universal Programmer:

Step 1:
Acquire a "Universal Programmer". UC Micro System's UNIPro 110u is one such programmer. The photos below explains the process of restoring the bootloader using this programmer. The procedure for doing the same using a different brand of universal programmer would be similar.

Step 2:
Download and install the universal programmer's PC frontend software. In case of UNIPro 110u you can get the latest version from here (as of the day of posting this blog, the latest version was 4.20 and it did not yet work on Windows 7).
Step 3:

Visit the "P89V51RB2_RC2_RD2 Product Information Page" at NXP here.
At the bottom of this page, you will find a link: "P89V/LV51RD2 Boot Loader update V5" (Direct link to ZIP file)
Download this ZIP archive (p89v_lv51rd2_bl_upd.zip). It contains the bootloader HEX file.
Within this ZIP archive, you will find two HEX files. We are interested only in P89V51RD2_BL_V05.hex. (The other HEX file is for updating the bootloader via flashmagic in cases where the original bootloader is still intact inside the microcontroller)

Step 4:
Select the microcontroller in the programmer frontend software.

Step 5:
Select the HEX file: P89V51RD2_BL_V05.hex

Step 6
Press the program button! (In case of UNIPro 110u, ignore the "Need AC Adaptor message" - USB power is enough to program P89V51RD2)

If the microcontroller gets programmed successfully, then the bootloader would now reside in the flash memory of the microcontroller. The microcontroller will now work again with FlashMagic.

NOTE regarding updated bootloader:
An updated version for the bootloader for P89V51RD is available from FlashMagic's website. Direct link here. Read the enclosed PDF file in the ZIP archive to know how to use it.

NOTE for microcontrollers manufactured by SST:
This process will also work with SST89E516RD (manufactured by SST) whose bootloaders are corrupted.
EasyIAP (which is equivalent in functionality to FlashMagic) is used to communicate with SST89E516RD and download program into it.

While operating the Universal Programmer, you will need to select the microcontroller as "SST89E516RD". The bootloader for this microcontroller is available here. Download the ZIP archive named "IntMode_x5xx.zip" (direct link here). The bootloader is in form of a BIN file (instead of a HEX file) named "F51MBLL5.BIN".
The "IntMode_x5xx.zip" archive also contains the setup file for EasyIAP which is similar in functionality as FlashMagic but is instead used for programming SST's microcontrollers.

RC-5 Protocol (InfraRed)

2010-06-28T09:22:00.006+05:30

We have all used InfraRed based remotes to control various appliances around our house. All these remote work by transmitting data in form of flashes of infrared light - and wherever one needs to transmit data, there is always a protocol involved. The RC-5 protocol from Philips has been used in TVs, VCRs and other appliances since the past three decades. It was developed by Philips but was adopted by many other manufacturers.
Now days RC-5 has been superseded by RC-6 and various other protocols from various other manufacturers. These newer protocols have better features and are more flexible. San Bergmans's KnowledgeBase on Consumer IR is a nice place to lookup information (protocol specs, circuits, embedded code) on any of the old or new IR based protocols.

Here is how a RC-5 TV remote control transmitter unit looks like:

And here is a InfraRed receiver/demodulator:

A RC-5 codeword is 14 bit long. The first two are the start bits, then comes the toggle bit and finally the 5 bits of address and 6 bits of command code. The bits are manchester encoded and use a carrier frequency of 36kHz. By carrier frequency we aren't referring to the frequency of the infrared light used (which is around 300 TeraHertz) but the frequency at which the LED is flashed on and off. What all this means is that if we want to transmit a logic zero, we flash an infrared LED 32 times at 36kHz (which takes 889 microseconds) and then keep it completely off for a time equivalent to 32 cycles at 36kHz (ie 889 microseconds). For logic one, we reverse the order (details here).

At the transmitter side, we use a transistor to control the blinking of the LED and at the receiver , a decoder, demodulates the received infrared light into pulses (which are still manchester encoded, although inverted). A common decoder used in receivers is TSOP1736.

Here is a screen shot of a 14-bit RC-5 codeword as demodulated by the InfraRed Receiver. The signal has been saptured using a sound card.

And here are a few (progressively zoomed in) screenshots of waveforms captured on a PC based Oscilloscope. The signal on channel 1 is captured on the base of the transistor controlling the IR LED on the transmitter unit. The singal on channel 2 is captured at the output of the decoder on the receiving unit. Note the obvious delay between the transmitted signal and the decoded signal. You can count the number of pulses in the transmitted half bit is exactly 32 (compare it with waveforms on the wikipedia article).

The RC-5 decoder and remote control are present on the UNI-51-SDK, UNI-51-SDKmkII and UNI-PIC-SDK. These are development kits available from UC Micro Systems. You can acquire these kits if you want to experiment with RC-5 protocol and develop application around it (like remotely switching on/off appliances)

Addendum: Here is a photo of assorted infrared devices:

The ones in the center and top right are IrDA transceivers and the rest are InfraRed Demodulators (used for RC-5 decoding)

I2S

2010-06-25T11:33:00.005+05:30

I²S stands for Inter Integrate Sound and is similar to the I²C which is used for transmitting data between Chips on a circuit board. (wikipedia article on I²S). I²S is used for connecting digital audio devices together, (for example between the main processor and the audio codec chip on cell phones or computers or between the CD transport and the DAC in a CD player).
I²S interface consists of atleast 3 signals:

Clock
Left right clock
Data line

The eKA8562A Chip which is a USB Audio Controller (and can be used as an oscilloscope) sports an I²S interface. Here are a few signals captured at the various pins (I²S output) on this chip:

Pin 5 of eKA8562A - I2S BCLK Output
Clock - This signal is used as the clock to latch in the bits appearing on the data line.

Pin 6 of eKA8562A - I2S LRCLK Output
Left Right Clock - This signal is used to tell the receiving device whether the data being received by it on the data line is meant for the left audio channel or the right audio channel.

Pin 7 of eKA8562A - I2S SDATA Output
Data - This signal carries the actual PCM audio data alternately for the left and the right audio channels.

Since eKA8562A is a USB device, it uses a 12MHz Crystal as its clock source:

12MHz Clock on a USB Device: Pin 4 of eKA8562A

Poor student's oscilloscope

2010-05-27T14:57:00.014+05:30

Enterprising undergrad engineering students can achieve a lot if given the right set of tools. Once you level up to designing some complex circuits, a signal generator and an oscilloscope would definitely go a long way in helping you in debugging your projects. I bought my first oscilloscope (Acute DS1202 200MHz PC based) for INR 37,500 after accumulating my salary for 4 months at my first job. But I always wished I has an access to an oscilloscope as a student. It seems that now days there is a low cost option for students to use: the PCs sound card.
Most modern motherboards have an onboard Audio Codec Chip which is used to accept and output sound, you can find atleast 3 audio jacks labeled Microphone, Line In and Line Out on the back side of your CPU Cabinet. You can then use specialized freeware/shareware applications which can turn your PC into an Oscilloscope/Signal Generator. Here are screen shots of some of these:

Oscilloscope 2.51 (aka Winscope) - the captured waveform is of the character 'a' being transmitted from a microcontroller UART at 9600 bits per second 8-N-1

Soundcard Oscilloscope 1.32 - the captured waveform is of the RC-5 packet as decoded by an InfraRed Receiver

There is also a concern that you may exceed the input voltage range and blow up the sound codec chip on your motherboard, so for that one can buy a cheap USB Audio Controller. These cost somewhere around Rs. 325 in India and so you won't feel that bad when you blow it up! These USB Audio Controllers show up as a standard Audio Controller in Windows Device Manager and can be used like a standard sound card. They are actually ment for use with VoIP applications like Skype, but we can surely use them for different purposes. Here are photos of two of these:

This one is based on the CM108 Chip

And this one on the eKA8562A Chip

So all you need to do to capture a signal is use a wire with 3.5mm mono audio lead at its end plugged into the microphone jack. If your audio controller has a "line in jack", you can capture two signals on the left and right channels. To use line-in you will require a 3.5mm stereo lead (instead of mono lead for microphone). The speaker out can be used as a dual channel signal generator when coupled with the proper software (e.g. Soundcard Oscilloscope 1.32 linked to above)

Also checkout this project: Sound card based multimeter
and another sound card based oscilloscope software: Zelscope

I guess it is also possible to re-purpose bluetooth headsets available now days into low bandwidth wireless oscilloscopes - how cool would that be? You can pair up bluetooth headsets (including those equipped with A2DP) with your windows based PCs running BlueSoleil. Should try that out one of these days.

There is another piece of cool software that one should be aware of: imagine you are in an aircraft (or a train) traveling to someplace and you have lots of time to kill. If you have friends/family traveling with you, then all of you can watch a movie on a laptop - the only problem would be to have multiple set of headphone. Rather than loading a single headphones jack with multiple headphones using a Y-splitter, you can plugin multiple USB audio controllers into your laptop and use Virtual Audio Cable to replicate audio stream to multiple devices. In case you decide to do this, you will also have to adjust the audio/video delay for this - all extra processing causes the video and audio to fall out of sync. If you are using the latest version of VLC media player, you can adjust the audio delay (with respect to video) using "j" and "k" keys - or you can try this. Virtual Audio Cable can also be used to record audio streams from various application (eg Youtube flash video being played from within Firefox, or music played while playing a game, or your conversation while talking to someone on Skype).

GSM 217Hz TDMA noise

2010-05-27T13:11:00.004+05:30

Bring a GSM cellphone near some low grade audio equipment and you can hear some very irritating noises. GSM or Global System for Mobiles uses FDMA, TDMA and SDMA for providing network access to multiple users. This each achieves as follows: Base Transceiver Stations within Cells (a fundamental unit of geographical areacovered by the GSM service provider) surrounding a given cell will all use frequencies different from each other (Frequency Division Multiple Access). The maximum amount of power transmitted by BTS as well as mobile units within a given cell is limited and so cells separated by a considerable geographical area can both reuse the same frequency for transmission (Space Division Multiple Access). And finally within a given cell, mobile units will use Time Division Multiple Access so that man users can be served by the same Base Transceiver Station. Of course different frequencies are used for uplink and downlink. Depending on the country, GSM operates in 800MHz to 900MHz or 1800MHz to 1900MHz bands.

With regards to TDMA, a GSM multiframe lasts 120 milliseconds consists of 26 frames. each of these frames itself last 4.61538 milliseconds and have 8 timeslots each. During a simple conversation, each of these is allotted to a different user - so a cell phone (in an active call) sends a burst of data every 4.61538 milliseconds which results in a 217 Hertz pulse waveform which lies in the audible range and gets coupled into unshielded audio circuits operating in the vicinity of the cell phone.

Of course if you bring an oscilloscope probe near a cellphone and make a call, you can observe these bursts too:

The horizontal scale is 20 milliseconds, you can note that the time between two bursts is approx 4.6 milliseconds. The above waveforms have been captured on a Tektronix TDS3044B Digital Phosphor Oscilloscope with 350MHz bandwidth. While I was trying to get a proper waveform for the 217Hz noise, I ended up capturing some vivid patterns on the scope. These too were captured while the cellphone was on an active call. Note that these waveforms have been improperly captured and cannot be used to deduce much useful information about the signal:

I was also able to capture a clean waveform of the noise induced by a cell phone in a nearby landline telephone - note that the duration of 4.6 milliseconds between two successive bursts is clearly seen. The signal was captured by touching the probes directly to the two wires of the telephone lines.

RF Frequency Modulation

2010-05-27T11:56:00.006+05:30

Visha Electronics carries a very low cost FM transmitter kit based around BF494 NPN Bipolar Junction Transistor. The kit has a condenser microphone to pickup sound. A variable capacitor is also present to tune the transmission frequency anywhere in the 88-108 MHz range. The transmitted signals can be picked up by any stand radio receiver. A simple receiver circuit can also be built, like the one shown here.

Please visit http://www.vishaworld.com for details on more such kits. Students are invited for workshops/courses at our LARE Learning Center for an opportunity to assemble and experiment with such kits.

Serial Peripheral Interface

2010-05-27T10:36:00.007+05:30

SPI is a serial link standard used between chips. Now days most microcontrollers have an on board SPI block. SPI link is made of atleast one master and one slave. The link is composed of four wires:

SCLK - Serial Clock, always provided by the Master
MOSI - Master Out Slave In, Data (from master to slave)
MISO - Master In Slave Out, Data (from slave to master, clock still has to be provided by master)
nSS - Slave Select, usually the Chip Select signal for the slave.

Sensors, ADC/DAC, memory and many other devices had slave SPI interfaces. Some examples of SPI compatible ICs/Devices:-

Accelerometers (ADIS16201)
4-20mA current control (AD420)
Flash Memory (EN25T80)
Nokia 6610 Colour Graphical STN LCD (PCF8833)
Nokia 3310 Monochrome Graphical LCD (PCD8544)
EEPROM (25AA640)
SD Card
10BASET Ethernet Controller (ENC28J60)

Many microcontrollers - like AT89S52 and all the AVR devices available from Atmel - are programmed via SPI.

Here is a screen shot of SPI signals captured as a master sends a byte to a slave:

All signals captured are from microcontroller (master) to slave device
Channel 4: nSS
Channel 2: SCLK
Channel 3: MOSI
In this particular case, each data bit is clocked in by the slave device at the falling edge of the clock. Some slaves sample the data at the rising edge.

Binary Phase Shift Keying

2010-05-26T23:02:00.003+05:30

Here are some photos and waveforms from a PSK generation lab practicals. All undergraduate students pursuing engineering in electronics and its allied fields get a chance to do it at least once during their four years.
The process of PSK generation in a lab is as follows:

Generate a sinusoidal carrier wave from a signal generator. Call it Signal A
Use an operational amplifier to shift the phase of Signal A by a fixed amount : usually 90 degrees in case of Binay Phase Shift Keying. Call this Signal B.
Apply Signal A and Signal B to the two inputs of a 2:1 analog multiplexer.
Apply the data signal to the select line of the analog switch. The output of the analog switch will be the required PSK signal. The data signal is a simple digital signal with two states 1 and 0 i.e. 0 and +5V. This can be emulated using a 555 Timer wired to generate a simple square wave. The analog switch will select Signal A or Signal B depending on the logic level of this data signal thereby outputting a sine wave which abruptly changes phase as the bit value changes.

Highway Addressable Remote Transducer Protocol

2010-05-25T16:12:00.006+05:30

HART is a digital industrial automation protocol which has been in use for quite some time now. It uses "Continuous Phase" Frequency Shift Keying to transmit data over the same wires (a pair of wires - one for each direction of flow of current) which had been used for 4-20 mA current loop signaling. bit 1 is represented by a sinusoid at 1200 Hz and bit 0 is represented by a sinusoid at 2200 Hz. The signal has an amplitude of 1mA peak to peak (current signaling):

Top: HART Signal Below: Data Transmitted

The HART Packet consists of a sequence of fields each consisting of varying number of bytes:

Various fields of HART Packet sent from Master to Slave

Each byte is it self a standard UART frame sent out at 1200 bps in 8-O-1 format. So a PC equipped with a serial port can act as a master simply by using a HART modem and appropriate application:

A HART Modem (black device with white sticker on right) from MACTek. The PCB shown here is used to sniff the data being sent from the PC to the modem.

Windows Application - VIATOR Check utility that came with the MACTek HART Modem.

Of course one can use good ol' DOS prompt too to send data out the serial port using simple commands.

And finally here are a the captured waveforms of a HART frame being transmitted:

Measuring the frequencies for Bits 1 (1200 Hz) and 0 (2200Hz). FFT of the signal clearly shows peaks at these two frequencies:

And finally one can use Serial Monitor from HHD Software to monitor the data being sent out the serial port by any Microsoft Windows based application running on your PC. Here are some screen shots:

Square Wave: Zooming in!

2010-05-22T01:41:00.001+05:30

Oscilloscopes are fun. And I like collecting stuff. So inevitably this led me to start collecting "waveforms" of common signals propagating in and between the various electronic equipment that run our lives.
First up is a simple square wave captured on a Tektronix TPS2024 oscilloscope. The square wave is taken from the oscilloscope itself and is actually meant for probe calibration/compensation. The square wave is 1KHz 5volt peak to peak. The animated GIF file below shows the square wave at each step as the time division knob is moved . I always wanted to make such an animation - sort of satisfies our inherent kiddish desires to play with knobs and buttons and move them/bang on them randomly madly!

Here is an FFT (Hanning window) of the above waveform:

Measuring some characteristics of the square wave using oscilloscope's built-in features:

Transient analysis (rise time measurement) of the above square wave:

S.M.Dees: The Album!

2010-04-16T23:06:00.000+05:30

So how do you explain about Integrated Circuits and IC Packages, about thru hole and SMDs, and electronic components - in general - to a fresher undergrad engineering student?

Of course you go about by getting them to open up old electronics devices and letting them observe the various printed circuit boards installed in those devices. You can then point out the various components soldered on to the boards to help them get started with identifying the kind and package of each components: "This one's a 33 kiloohms 0805 resistor, and thats a Case B 10 microfarad 35 volts Case C Tantalum Capacitor and that big flat black thing there is a 240 Pin 0.5 mm pitched LQFP package - an Application Specific Integrated Circuit - the brains which used to make this DVD writer drive work its magic!"

So after you are done breaking things apart and guiding the students through the component "jungles" inside modern day electronics, you realize that they would still need a ready reckoner which they can refer to regularly till they have built up enough confidence to identify components in various packages and so here's what we came up with:

We stuffed a coin album from Archies (a novelty/gift brand in India) with as many variety of components as we can find. The album had 8 sheets, we used the alternate sheets to hold labels for the components held in the preceding sheet. The labels themselves are colour coded - different label colour for different kind of components - sky blue for ICs, tan for diodes, parrot green for crystals and so on. Here are the scans of each of the 4 pair of sheets:

Sheet 1 - SMD ICs:

Sheet 2 - SMD ICs and SMD Passives:

Sheet 3 - thru hole Passives:

Sheet 4 - thru hole Passives:

Extra Sheet - a thin slice (wafer) of silicon with transistors etched on it :

We use such teaching aids at LARE's Learning Center, India during practical hands-on courses for undergraduates in the field of embedded electronic design. Do join us for a unique learning experience and go beyond your academic courseware!

Using Showcase Pieces at Learning Center

2010-04-16T01:56:00.007+05:30

Many manufacturers send distributors & shopkeepers a collection of samples of their products to display in their showcases for customers. We figured these can prove to be a great teaching aid for students - a nice tangible way to introduce them to the wide variety of electronic components available to an engineer today. Here is one with samples of a variety of Screw Terminals:

LARE's Learning Center, India conducts practical hands-on courses for undergraduates in the field of embedded electronic design. Do join us for a unique learning experience and go beyond your academic courseware.

See my 8051 Collection !

2010-04-16T01:07:00.009+05:30

While working on new chapters for Kenneth J. Ayala's Book on 8051 Microcontroller with Prof. Dhananjay Gadre, I had this desire to collect as many actual samples of 8051 variants as possible. I already had a sample of the original 8051 and Gadre sir was able to find me some 87C51s. I was able to add some more samples to my collection over the past 2 years. I put them all in a nice box, labelled them and presented the collection to LARE's Learning Center, Belapur, India for use as a teaching aid during their workshops/seminars/courses. Its fun to collect stuff! I hope this collection will help students realize the ubiquity of the 8051 based microcontrollers - they come in all sizes and have a wide range of feature sets, and even today they are installed in way too many systems as compared to other family of microcontrollers. Here are a few snaps of my humble collection:

The Box:

The 8051s:

Their labels on the box covers (part numbers and specs - image mirrored & rotated)

The SMD ones in detail:

Keil maintains a database of datasheets of all 8051 variants.

Inside a Bourns 3296 Potentiometer

2010-04-15T16:45:00.007+05:30

Taking things apart to see how they work is the most fun that we get to do. Here's what a Bourns 3296 Potentiometer looks from Inside. You can easily make out how the multiturn feature works - there is a screw and cog arrangement. The cog carries the brush which moves the electrical position of the center tap along the circular cermet track (black coloured). Cermet is a ceramic/metal mixture. Do checkout Wikipedia's entry on Potentiometers.

Mesmerizing Masses of Microcontrollers

2010-04-04T21:00:00.009+05:30

One "P89V51RD2 Microcontroller BreadBlock" :

Many "P89V51RD2 Microcontroller BreadBlocks" :
(Panelized for ease of manufacture, these panels when panelized make for nice desktop wallpapers)

Assorted SMD Components

2010-03-23T15:44:00.007+05:30

Here is a high resolution scanned image of assorted SMD components.
It took me one hour to place the components on the scanner glass and scan it at 1200dpi.
Why did I do it? I don't know, just like that.
Actually, this pic is quite useful to acquaint an engineering student with various SMD packages:
SOT23, TQFP, SOIC, TSSOP, Case B, 0805, MELF, QFN ... blah blah blah..

Here is the full A4 size image (low res.):

Here are the various sections of the above image in high resolution:

Jugaad: VCD skip prevention

2010-03-23T01:51:00.003+05:30

A picture speaks better than a thousand words and "jugaad" is a word best defined thru pictures, so I will be putting up photos of jugaads whenever I come across them.

Jugaad inside an intercity Bus (Chandrapur <> Nagpur) to prevent VCD skipping due to jerks from potholes and bumps on the road:

Glut

2010-03-23T01:39:00.007+05:30

Lots of "lots ofs"

0.1 microfard Mylar Capacitors (5 mm pitch) (scanned 'em ;) ):

0.1 microfarad box capacitors:

ATmega8535L:

ATtiny2313:

SPDT Slide Switches:

3.6864 MHz Crystals:

Lots of random SMD components:

Capacitors: so many shapes, so many sizes, so irritating

2010-03-23T01:25:00.008+05:30

I made these two charts/pics as references for use while laying out PCBs:

Diameters of common thru hole cylindrical Electrolytic Capacitors

and Length and Breadths of SMD Tantalum Caps:

Notice that in thru hole electrolytic capacitors, the black band mark the negative terminals and in case of SMD tantalums, the black band marks the positive terminals. I learnt this the hard way - by soldering the tantalums the otherway round and watching them blow up. I wonder why some engineers make life so difficult for other engineers. How hard could it have been to follow the same standard on all kinds of polarized caps?

The Laboratory

2010-02-27T03:27:00.006+05:30

Here, are some pics of our Laboratory.
This lab is used by the Research Center and Design Services.
Notice how well organized the lab is - I know, I am actually trying to show off here :P

Link to the above album on Picasa (ie thumbnailed gallery)

Getting Serial Port to work under Ubuntu!

2010-02-04T14:51:00.019+05:30

The setup: I have a Intel motherboard inside my office desktop with a built-in serial port. Over the days, I managed to screw up the builtin COM port (and my friends at office did the same to their desktop PCs too.. haha!). What probably happened is that does to some ESD or overvoltage on one of the pins during experimentation caused the RS232 Driver on board the motherboard to get spoilt.
As a result, the COM port (COM1 in this case) was detected alright by windows XP but Bray's Terminal or Hyperterminal were either not able to receive or transmit data out of the port.

So we all got Serial Port PCI cards which costed around Rs.250 a piece. Each of these cards are based around the CH352 (more specifically CH325L) chip made by WCH (a chinese company).

WCH Website (Chinese): www.wch.cn
WCH Website (English): www.wch-ic.com
CH352 Product Page and Datasheet: http://www.wch-ic.com/product/pci/ch352.asp

All these cards have 2 Serial Ports on them. and they worked super fine on windows XP.
Then one day we all uninstalled Windows XP from our PCs and installed Ubuntu 9.10 x86 32bit. All of our hardware worked directly without any intervention on Ubuntu except the PCI Serial Cards.

Here is a list of what all I tried and what finally worked.

1) First I installed "Serial Port Terminal" from Ubuntu Software Center. This is actually "gtkterm"

2) Of course the serial ports werent working directly out of the box. The COM ports are named differently under ubuntu:

Windows Linux
COM1 /dev/ttyS0
COM2 /dev/ttyS1
COM3 /dev/ttyS2
COM4 /dev/ttyS3

Why? you ask: well under Linux and UNIX each and every hardware device treated as a file. These are called device files.
(as an aside: USB to serial convertors based around popular ICs like Prolific's PL2303 and FTDI's FT232RL work directly without any configuration on ubuntu. They appear as /dev/ttyUSB0 , dev/ttyUSB1 etc.
There is a blog post by swamytk on how to run FlashMagic (for programming P89V51RD2 microcontrollers via UART) on ubuntu using Wine: here . In the comments section on that page you can see how to redirect I/O from what appears as COM1 to /dev/ttyUSB0 - which is what USB-Serial convertors appear as under ubuntu)

Googling led me to the command for listing all the serial ports under ubuntu:

setserial -g /dev/ttyS*

But before you use that command, you will need to install the setserial package. You can install that by going over to Synaptic Package Manager and searching for and installing "setserial". Alternatively you can issuse the command "sudo apt-get install setserial" at the terminal prompt.

The output of the setserial -g /dev/ttyS* came out as:

/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: undefined, Port: 0x1108, IRQ: 18
/dev/ttyS2, UART: undefined, Port: 0x1100, IRQ: 18
/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3

The first entry was of /dev/ttyS0 which would have been COM1 on Windows. Thats the motherboard's detectable but nor working COM port. The entries for ttyS1 and ttyS2 had the same Interrupt Request Number and so I knew those were the entries for the two serial ports on the PCI card that I had installed. The number "16550A" refers to the UART type. 16550 is the part number of the IC invented by National Semiconductor which was first used to implement UART. Read more about 16550 UART and 16550A (improved version) on wikipedia.

The output of lspci -v command for the serial port PCI card was:

05:04.0 Serial controller: Device 4348:3253 (rev 10) (prog-if 02)
Subsystem: Device 4348:3253
Flags: medium devsel, IRQ 18
I/O ports at 1108 [size=8]
I/O ports at 1100 [size=8]
Kernel driver in use: serial

and some of the serial port related system messages uncovered by dmesg were:

[ 0.808748] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
[ 0.808852] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
[ 0.809268] 00:0a: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
[ 0.809362] serial 0000:05:04.0: PCI INT A -> GSI 18 (level, low) -> IRQ 18
[ 0.809438] 0000:05:04.0: ttyS1 at I/O 0x1108 (irq = 18) is a XScale
[ 0.809530] 0000:05:04.0: ttyS2 at I/O 0x1100 (irq = 18) is a XScale

3) Next I found the driver CD that came with the PCI card. There was a linux driver for the card on it. There was am executable file named "ch35x_80x86.o" on it. The instructions were as follows:

This installation guide describes the procedures to install and uninstall CH35X PCI to two serial ports,one serial and one parport,
two serial ports and one parport,four serial ports in Linux platform.
1-install and uninstall CH35X PCI boards

(1)-install
<1>-copy ch35x_80x86.o to /usr/sbin
<2>-Add /usr/sbin/ch35x_80x86 at the end of the /etc/rc.d/rc.local.
<3>-reboot
if you inster two serials port board
The ttyS2 and ttyS3 are ready for application.

if you inster one serial port and one parport port board
The ttyS2 and LPT1 or LPT2 ready for application.

if you inster four serials port board
The ttyS2 ttyS3 ttyS4 and ttyS5 are ready for application.

if you inster two serials port and aone parport port board
The ttyS2 ttyS3 and LPT1 or LPT2 are ready for application.

(2)-uninstall
(1)-Remove /usr/sbin/ch35x_80x86 at the end of the /etc/rc.d/rc.local.
(2)-Remove /usr/sbin/ch35x_80x86.o

Of course this didnt work (note that on ubuntu, the file to be modified is "/etc/rc.local" instead of "/etc/rc.d/rc.local". You will have to do sudo gedit /etc/rc.local to edit that file.)

4) While I was doing all this (people with similar problems), my friend Rajesh somehow got the serial port to work on his PC. When we asked him how he did it, he said he didnt know. Being complete a n00b to linux (that includes all of us!) , he had forgotten that led him to get it to work. We tried gtkterm on his PC and shorted pins 2 and3 on the RS232 Connector and could see the characters being echoed back!
the setserial list command on Rajesh's PC yielded:

/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: 16550A, Port: 0x9000, IRQ: 19, Flags: spd_cust
/dev/ttyS2, UART: 16550A, Port: 0x9400, IRQ: 19
/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3

which led me to believe that maybe the PCI was detected properly on my PC but the linux's serial driver didnt know what kind uart was there on the PCI card.

Further surfing on the web saw me stumble acrosss the following link: http://serial.sourceforge.net/
which is the Project repository for the Linux Serial Driver. The page refers to using the lspci-v command to get port address information about your PCI card and then using the information with setserial command to get your serial ports working. Here is the extract:

Hopefully, there are one or more I/O port regions associated with the card. If you're comfortable using the setserial command, try setting one of your unusued /dev/ttyS devices to one of the I/O port regions listed by lspci, and set its IRQ to the IRQ listed by the lspci listing, and see if you can communicate to your serial port or your modem. I recommend using a low-level modem communications program such as C-Kermit for this testing purpose. If you find that some number of the lspci's I/O regions allow you to talk to the serial port/modem, let me know in your report to me.

Reading this give me inspiration to go and read the manual pages for setserial. (how many times have we heard RTFM thrown at our face!!)

Some points I picked up from the setserial man pages:

uart uart_type
This option is used to set the UART type. The permitted types
are none, 8250, 16450, 16550, 16550A, 16650, 16650V2, 16654,
16750, 16850, 16950, and 16954. Using UART type none will dis‐
able the port.

Some internal modems are billed as having a "16550A UART with a
1k buffer". This is a lie. They do not have really have a
16550A compatible UART; instead what they have is a 16450 com‐
patible UART with a 1k receive buffer to prevent receiver over‐
runs. This is important, because they do not have a transmit
FIFO. Hence, they are not compatible with a 16550A UART, and
the autoconfiguration process will correctly identify them as
16450's. If you attempt to override this using the uart parame‐
ter, you will see dropped characters during file transmissions.
These UART's usually have other problems: the skip_test parame‐
ter also often must be specified.

..I can live with a few dropped characters.. as long as my serial works!!

MULTIPORT CONFIGURATION
Certain multiport serial boards which share multiple ports on a single
IRQ use one or more ports to indicate whether or not there are any
pending ports which need to be serviced. If your multiport board sup‐
ports these ports, you should make use of them to avoid potential lock‐
ups if the interrupt gets lost.

In order to set these ports specify set_multiport as a parameter, and
follow it with the multiport parameters. The multiport parameters take
the form of specifying the port that should be checked, a mask which
indicate which bits in the register are significant, and finally, a
match parameter which specifies what the significant bits in that reg‐
ister must match when there is no more pending work to be done.

...this multiport thing was probaly applicable to my card, but I thought lemme first get the ports working, and so I issued the following two commands to for the serial driver to think of my ports as 16550A:

sudo setserial /dev/ttyS1 uart 16550A
sudo setserial /dev/ttyS2 uart 16550A

and lo! and behold! they started working!! used gtkterm with 2 and 3 pins shorted and I was able to get the echo back!

The setserial -g /dev/ttyS* now yields:

/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: 16550A, Port: 0x1108, IRQ: 18
/dev/ttyS2, UART: 16550A, Port: 0x1100, IRQ: 18
/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3

Elecrama 2010

2010-01-26T13:30:00.003+05:30

LARE & UC Micro Systems had put up a stall at Elecrama 2010 (20th to 24th January).
We got a fantastic response from all kinds of visitors - professionals and students alike. (Being one of the handful few of electronics based company in a large exhibition full of electrical companies did help! :) )

Here are a few pics from the event:

Number Plate of an Engineer

2010-01-20T13:34:00.008+05:30

What better way to say "Hey! this car belongs to an Embedded Systems Engineer!!!"
Of course when I get one, it will be some swanky one with AUTOSAR compliant interconnected (via FlexRay/LIN/CAN) ECUs.

By the way this number plate is actually cool in one other way too... MFC stands for Microsoft Foundation Classes - which projects the image that the owner is a complete hardware AND software geek!!

Wireless Photography!!

2010-01-06T11:51:00.031+05:30

We needed to take photos of our products (mainly UNIBlocks) and put them on our online webshop. We were impressed by the product photos put up on their websites by a few other similar companies based in countries other than India (like Sparkfun, Jee Labs and Seeed Studios). So we set out on a quest for "technology and methodology" for taking the perfect photo of our products. We had a DSLR camera (Nikon D40x), but we needed something more. And since we were at it, I thought why not try to make the whole photography process simpler - so that even those who were new to DSLRs and expensive studio equipment, could easily and swiftly take good photos.

Step 1) Eye.fi

The first step was to get a eye.fi card. Having a way to quickly and conveniently pull a photo from the camera (and that too wirelessly!) would be super useful - I would be able to look at the final photo immediately after clicking it and check if it has come out properly. This minimizes the time for arriving at optimal settings for a particular scene via the "trial and error" method.

eye.fi is a small PCB with a microprocessor (running an OS), some flash memory and a WiFi Chipset all packaged inside a standard SD card connector. It works just like a standard SD card. The camera saves photos on the card and after doing that, the card sends the photos over WiFi to your PC.

eye.fi's aren't available in India. So I asked one of my friends in US, to buy one and send it to me - and I was pretty much impressed with the results!

Photo being transferred over WiFi (an application running in the background on your PC with its icon on the taskbar takes care of this):

The photo itself (of a laptop RAM module):

Nokion D40x Loaded with an eye.fi:

eye.fi's are available in many variations, some can upload photos directly to flickr/picasa, others can transfer videos and raw files. You can check out their website to see which options suit you best. In our case, the simplest one which could transfer pictures to a PC was all that was needed.

2) The digital lights, boom and a wireless trigger!

Since I knew zilch about professional studio equipment, I turned to a friend of mine. Tejal and I were classmates for 4 years at our undergrad college - Vivekanand. Tejal works with her dad who is a professional photographer and has his own studio. I had been pestering her to allow me to install an eye.fi card in one or more of her cameras (and a wifi router) at her studios to ease their workflow and to help me buy equipment for my own customized mini studio. So we set out to upgrade her sudio and setup my own. After looking at the products whose photos I wanted to take, Tejal's dad suggested that a pair of digital studio lights would do the trick. So they graciously agreed to help me with that, and after they were done, I had a complete mini-studio at my workplace.

They got me two digital lights:

And a super-boom to hold the camera in place in case I needed to take shots from vertically up. I got a low but wide plastic table and put a white plastic sheet (which Tejal and uncle had got for me too) over it to form a nice tabletop on which I would the stuff I wanna take photos of. The super-boom was mounted on a thick stainless steel pipe which could be rotated sideways along the vertical axis. Since the super-boom was heavy, we had to add an extra piece of support midway. The whole setup finally looked like this:

One very important piece of equipment which Tejal and her dad got me was the wireless trigger. The system has two parts, one of them fits over the camera (the socket which is meant for attaching a flash), and the other sits on one of the studio lights (connected in series with the power supply to the light). When you click a picture, the module sitting over the camera wirelessly sends a signal to the receiver connected to one of the lights. The receiver fires the flash trigger of the light to which it is connected. The optical sensor on the second studio light senses the flash from first light and triggers its own flash. The DIP switches on the wireless trigger system allow addressability - so in effect if u have a huge studio with multiple people working, you can have upto 4 wireless trigger systems working simultaneously without cross triggering each other.

Wireless trigger transmitter:

Wireless trigger receiver:

3) The Infrared Remote camera trigger

There is an optional accessory which one can buy for Nikon D40x, its an infrared remote control (called ML-L3) for triggering the camera to click a picture from a distance. This is specially useful if you have mounted the camera on a tripod with an intention of clicking picture with yourself in it. So I asked Tejal's dad to get me one.

After the whole setup was done, I couldn't help but grin - pondering over the seemingly magic created by the convergence of technologies:

I use an infrared remote control to WIRELESSLY trigger the camera which clicks a photos while simultaneously triggering the studio lights WIRELESSLY using RF. The photo itself is then WIRELESSLY transmitted to my desktop computer sitting next door using WiFi!. The photo appears on my laptop sitting in the studio over a Network Share accessed WIRELESSLY over WiFi - What Fun!

Clicking crisp photos of electronics has become a pleasant and fun experience. The photos put up for the UNIBlocks at shop.lare.in have all been taken by this setup. Here are a few samples:

(Thank you Tejal, and thank you Uncle for making this happen!)

If your camera uses a CompactFlash Card instead of an SD Card, consider acquiring

Synchrotech's CFMulti CompactFlash Type II to Eye-Fi™ + Multi-Card Adapter (link):

Logos!

2009-12-28T12:17:00.004+05:30

We already have a nice sweet logo for LARE. (See the banner above)
But as a company whose major business lies in designing electronics, a simple logo is very desirable. The aim is that the logo's design should lend itself to convenient reproduction via any of the huge variety of processes. For example, the fabrication process for Printed Circuit Boards requires that the logo should be made of monochromatic line art. Here are a few trials by my "confederate in crazy/creative works" towards designing an alternative logo for LARE.

Have to admit, trying out various designs for a logo is good fun!

Here is a scan of a PCB Panel during when we were trying out various designs for UNIBlocks:

Here is a scan of a small PCB with LARE logo on it. The logo has come out sad isn't it!

WRT54GL & UNIBlocks

2009-12-25T02:24:00.012+05:30

Linksys WRT54GL is a well known very hackable WiFi router.
Of the numerous open source (and some closed source) software available for extending the functionality of this router, DD-WRT is the most popular. DD-WRT is a linux based replacement firmware (Wikipedia Entry | Official Site).

DD-WRT allows one to connect a SD Card to the router. The SD card can be used to store logs, webpages etc..
The following webpages describe the hardware modification required to add a SD Card to the router:
DD-WRT Wiki | craig at powco

DD-WRT also dumps system messages one one of its two serial ports. The serial ports can be accessed by connecting then to your Computer's COM Port via a RS-232 Level Translator. The modification goes something like this.

Well, as it turns out, UNIBlocks are pretty convenient to get these mods done. Here are some photos on how I did it!

Here is the screen shot of the console output I received from DD-WRT over Serial Port 0 when I first attached a 16MB SD Card to it. The 1GB SD card show in the photo above was giving me problems (it was probably because of the bad flash block that it might have developed over the months of use or might be because that support for larger memory cards in DD-WRT is not complete, I had also tried to work a brand new 2GB SD card with it - the router detected the card alright this time but it kept rebooting!):

Screenshot of the webpage showing the memory capacity of the SD Card:

And finally, you can use WinSCP to browse the file system on the router and copy files to and fro. The SD card is formatted automatically by the router with the ext2 filesystem. The card is mounted in /dev/mmc.
More on this here: http://www.dd-wrt.com/wiki/index.php/WinSCP

Here's text for the console output:

CFE version 1.0.37 for BCM947XX (32bit,SP,LE)
Build Date: Tue Jun 20 16:22:41 CST 2006 (root@localhost.localdomain)
Copyright (C) 2000,2001,2002,2003 Broadcom Corporation.

Initializing Arena
Initializing Devices.

No DPN
et0: Broadcom BCM47xx 10/100 Mbps Ethernet Controller 3.90.37.0
CPU type 0x29008: 200MHz
Total memory: 16384 KBytes

Total memory used by CFE: 0x80300000 - 0x803A39C0 (670144)
Initialized Data: 0x803398D0 - 0x8033BFE0 (10000)
BSS Area: 0x8033BFE0 - 0x8033D9C0 (6624)
Local Heap: 0x8033D9C0 - 0x803A19C0 (409600)
Stack Area: 0x803A19C0 - 0x803A39C0 (8192)
Text (code) segment: 0x80300000 - 0x803398D0 (235728)
Boot area (physical): 0x003A4000 - 0x003E4000
Relocation Factor: I:00000000 - D:00000000

Boot version: v3.7
The boot is CFE

mac_init(): Find mac [00:1A:70:5A:92:0D] in location 0
Nothing...

eou_key_init(): Find key pair in location 0
The eou device id is same
The eou public key is same
The eou private key is same
Device eth0: hwaddr 00-1A-70-5A-92-0D, ipaddr 192.168.1.1, mask 255.255.255.0
gateway not set, nameserver not set
Reading :: Failed.: Timeout occured
Loader:raw Filesys:raw Dev:flash0.os File: Options:(null)
Loading: .. 3856 bytes read
Entry at 0x80001000
Closing network.
Starting program at 0x80001000
CPU ProcId is: 0x00029008, options: 0x0000004d
Linux version 2.4.37 (root@dd-wrt) (gcc version 3.4.6 (OpenWrt-2.0)) #7585 Sat Oct 10 02:08:51 CEST 2009
Setting the PFC to its default value
Determined physical RAM map:
memory: 01000000 @ 00000000 (usable)
On node 0 totalpages: 4096
zone(0): 4096 pages.
zone(1): 0 pages.
zone(2): 0 pages.
Kernel command line: root=/dev/mtdblock2 rootfstype=squashfs,jffs2 noinitrd console=ttyS0,115200
CPU: BCM5352 rev 0 at 200 MHz
Using 100.000 MHz high precision timer.
Calibrating delay loop... 199.47 BogoMIPS
Dentry cache hash table entries: 2048 (order: 2, 16384 bytes)
Inode cache hash table entries: 1024 (order: 1, 8192 bytes)
Mount cache hash table entries: 512 (order: 0, 4096 bytes)
Buffer cache hash table entries: 1024 (order: 0, 4096 bytes)
Page-cache hash table entries: 4096 (order: 2, 16384 bytes)
Checking for 'wait' instruction... unavailable.
POSIX conformance testing by UNIFIX
PCI: no core
PCI: Fixing up bus 0
Initializing RT netlink socket
Starting kswapd
devfs: v1.12c (20020818) Richard Gooch (rgooch@atnf.csiro.au)
devfs: boot_options: 0x1
squashfs: version 3.0 (2006/03/15) Phillip Lougher
pty: 256 Unix98 ptys configured
Serial driver version 5.05c (2001-07-08) with MANY_PORTS SHARE_IRQ SERIAL_PCI enabled
ttyS00 at 0xb8000300 (irq = 3) is a 16550A
ttyS01 at 0xb8000400 (irq = 3) is a 16550A
PCI: Setting latency timer of device 00:01.0 to 64
PCI: Setting latency timer of device 00:05.0 to 64
sb_doattach: incoming bus is PCI but it's a lie, switching to SB devid:0x4320
PPPoL2TP kernel driver, V0.13
Universal TUN/TAP device driver 1.5 (C)1999-2002 Maxim Krasnyansky
Physically mapped flash: Found an alias at 0x400000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x800000 for the chip at 0x0
Physically mapped flash: Found an alias at 0xc00000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1000000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1400000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1800000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1c00000 for the chip at 0x0
Amd/Fujitsu Extended Query Table v3.3 at 0x0040
number of CFI chips: 1
cfi_cmdset_0002: Disabling fast programming due to code brokenness.
Flash device: 0x400000 at 0x1c000000
bootloader size: 262144
Physically mapped flash: Filesystem type: squashfs, size=0x2a491b
partition size = 2798592
Creating 5 MTD partitions on "Physically mapped flash":
0x00000000-0x00040000 : "cfe"
0x00040000-0x003f0000 : "linux"
0x00124c00-0x003d0000 : "rootfs"
mtd: partition "rootfs" doesn't start on an erase block boundary -- force read-only
0x003f0000-0x00400000 : "nvram"
0x003d0000-0x003f0000 : "ddwrt"
sflash not supported on this router
Initializing Cryptographic API
IP Protocols: ICMP, UDP, TCP, IGMP
IP: routing cache hash table of 512 buckets, 4Kbytes
TCP: Hash tables configured (established 1024 bind 2048)
ip_conntrack version 2.1 (512 buckets, 4096 max) - 336 bytes per conntrack
ip_tables: (C) 2000-2002 Netfilter core team
ipt_random match loaded
netfilter PSD loaded - (c) astaro AG
ipt_osf: Startng OS fingerprint matching module.
ipt_IPV4OPTSSTRIP loaded
NET4: Unix domain sockets 1.0/SMP for Linux NET4.0.
802.1Q VLAN Support v1.8 Ben Greear
All bugs added by David S. Miller
VFS: Mounted root (squashfs filesystem) readonly.
Mounted devfs on /dev
starting Architecture code for broadcom
Booting device: Linksys WRT54G/GL/GS
loading sysinit
boardflags are 0x2558
enable Afterburner, boardflags are 0x2758
sh: can't create /proc/switch/eth1/reset: nonexistent directory
sh: can't create /proc/sys/net/ipv4/tcp_congestion_control: nonexistent directory
mmc: starting module with: SD_DI=0x4, SD_DO=0x10, SD_CLK=0x8, SD_CS=0x80
Size = 14560, hardsectsize = 512, sectors = 29120
VFS: Can't find ext2 filesystem on dev mmc(121,1).
mke2fs 1.38 (30-Jun-2005)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
3632 inodes, 14528 blocks
726 blocks (5.00%) reserved for the super user
First data block=1
2 block groups
8192 blocks per group, 8192 fragments per group
1816 inodes per group
Superblock backups stored on blocks:
8193

Writing inode tables: done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 21 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
eth1: Operation not supported
wl0.1: No such device
wl0.2: No such device
wl0.3: No such device
eth1: Invalid argument
eth1: Invalid argument
br0: Bad file descriptor
br0: Bad file descriptor
eth1: Operation not supported
wl0.1: No such device
wl0.2: No such device
wl0.3: No such device
eth1: Invalid argument
eth1: Invalid argument
SIOCGIFFLAGS: No such device
vlan1: Setting MAC address to 00 1a 70 5a 92 0e.
SIOCGIFFLAGS: No such device
SIOCGIFFLAGS: No such device
SIOCGIFFLAGS: No such device
need_reboot=1: committing changes
ip_conntrack_pptp version 1.9 loaded
ip_nat_pptp version 1.5 loaded
nvram_commit(): end
Restarting system.
Please stand by while rebooting the system...

CFE version 1.0.37 for BCM947XX (32bit,SP,LE)
Build Date: Tue Jun 20 16:22:41 CST 2006 (root@localhost.localdomain)
Copyright (C) 2000,2001,2002,2003 Broadcom Corporation.

Initializing Arena
Initializing Devices.

No DPN
et0: Broadcom BCM47xx 10/100 Mbps Ethernet Controller 3.90.37.0
CPU type 0x29008: 200MHz
Total memory: 16384 KBytes

Total memory used by CFE: 0x80300000 - 0x803A39C0 (670144)
Initialized Data: 0x803398D0 - 0x8033BFE0 (10000)
BSS Area: 0x8033BFE0 - 0x8033D9C0 (6624)
Local Heap: 0x8033D9C0 - 0x803A19C0 (409600)
Stack Area: 0x803A19C0 - 0x803A39C0 (8192)
Text (code) segment: 0x80300000 - 0x803398D0 (235728)
Boot area (physical): 0x003A4000 - 0x003E4000
Relocation Factor: I:00000000 - D:00000000

Boot version: v3.7
The boot is CFE

mac_init(): Find mac [00:1A:70:5A:92:0D] in location 0
Nothing...

eou_key_init(): Find key pair in location 0
The eou device id is same
The eou public key is same
The eou private key is same
Device eth0: hwaddr 00-1A-70-5A-92-0D, ipaddr 192.168.1.1, mask 255.255.255.0
gateway not set, nameserver not set
Reading :: Failed.: Timeout occured
Loader:raw Filesys:raw Dev:flash0.os File: Options:(null)
Loading: .. 3856 bytes read
Entry at 0x80001000
Closing network.
Starting program at 0x80001000
CPU ProcId is: 0x00029008, options: 0x0000004d
Linux version 2.4.37 (root@dd-wrt) (gcc version 3.4.6 (OpenWrt-2.0)) #7585 Sat Oct 10 02:08:51 CEST 2009
Setting the PFC to its default value
Determined physical RAM map:
memory: 01000000 @ 00000000 (usable)
On node 0 totalpages: 4096
zone(0): 4096 pages.
zone(1): 0 pages.
zone(2): 0 pages.
Kernel command line: root=/dev/mtdblock2 rootfstype=squashfs,jffs2 noinitrd console=ttyS0,115200
CPU: BCM5352 rev 0 at 200 MHz
Using 100.000 MHz high precision timer.
Calibrating delay loop... 199.47 BogoMIPS
Dentry cache hash table entries: 2048 (order: 2, 16384 bytes)
Inode cache hash table entries: 1024 (order: 1, 8192 bytes)
Mount cache hash table entries: 512 (order: 0, 4096 bytes)
Buffer cache hash table entries: 1024 (order: 0, 4096 bytes)
Page-cache hash table entries: 4096 (order: 2, 16384 bytes)
Checking for 'wait' instruction... unavailable.
POSIX conformance testing by UNIFIX
PCI: no core
PCI: Fixing up bus 0
Initializing RT netlink socket
Starting kswapd
devfs: v1.12c (20020818) Richard Gooch (rgooch@atnf.csiro.au)
devfs: boot_options: 0x1
squashfs: version 3.0 (2006/03/15) Phillip Lougher
pty: 256 Unix98 ptys configured
Serial driver version 5.05c (2001-07-08) with MANY_PORTS SHARE_IRQ SERIAL_PCI enabled
ttyS00 at 0xb8000300 (irq = 3) is a 16550A
ttyS01 at 0xb8000400 (irq = 3) is a 16550A
PCI: Setting latency timer of device 00:01.0 to 64
PCI: Setting latency timer of device 00:05.0 to 64
sb_doattach: incoming bus is PCI but it's a lie, switching to SB devid:0x4320
PPPoL2TP kernel driver, V0.13
Universal TUN/TAP device driver 1.5 (C)1999-2002 Maxim Krasnyansky
Physically mapped flash: Found an alias at 0x400000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x800000 for the chip at 0x0
Physically mapped flash: Found an alias at 0xc00000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1000000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1400000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1800000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1c00000 for the chip at 0x0
Amd/Fujitsu Extended Query Table v3.3 at 0x0040
number of CFI chips: 1
cfi_cmdset_0002: Disabling fast programming due to code brokenness.
Flash device: 0x400000 at 0x1c000000
bootloader size: 262144
Physically mapped flash: Filesystem type: squashfs, size=0x2a491b
partition size = 2798592
Creating 5 MTD partitions on "Physically mapped flash":
0x00000000-0x00040000 : "cfe"
0x00040000-0x003f0000 : "linux"
0x00124c00-0x003d0000 : "rootfs"
mtd: partition "rootfs" doesn't start on an erase block boundary -- force read-only
0x003f0000-0x00400000 : "nvram"
0x003d0000-0x003f0000 : "ddwrt"
sflash not supported on this router
Initializing Cryptographic API
IP Protocols: ICMP, UDP, TCP, IGMP
IP: routing cache hash table of 512 buckets, 4Kbytes
TCP: Hash tables configured (established 1024 bind 2048)
ip_conntrack version 2.1 (512 buckets, 4096 max) - 336 bytes per conntrack
ip_tables: (C) 2000-2002 Netfilter core team
ipt_random match loaded
netfilter PSD loaded - (c) astaro AG
ipt_osf: Startng OS fingerprint matching module.
ipt_IPV4OPTSSTRIP loaded
NET4: Unix domain sockets 1.0/SMP for Linux NET4.0.
802.1Q VLAN Support v1.8 Ben Greear
All bugs added by David S. Miller
VFS: Mounted root (squashfs filesystem) readonly.
Mounted devfs on /dev
starting Architecture code for broadcom
Booting device: Linksys WRT54G/GL/GS
loading sysinit
boardflags are 0x2558
enable Afterburner, boardflags are 0x2758
sh: can't create /proc/switch/eth1/reset: nonexistent directory
sh: can't create /proc/sys/net/ipv4/tcp_congestion_control: nonexistent directory
mmc: starting module with: SD_DI=0x4, SD_DO=0x10, SD_CLK=0x8, SD_CS=0x80
Size = 14560, hardsectsize = 512, sectors = 29120
EXT2-fs warning: mounting unchecked fs, running e2fsck is recommended
eth1: Operation not supported
wl0.1: No such device
wl0.2: No such device
wl0.3: No such device
eth1: Invalid argument
eth1: Invalid argument
br0: Bad file descriptor
br0: Bad file descriptor
eth1: Operation not supported
wl0.1: No such device
wl0.2: No such device
wl0.3: No such device
eth1: Invalid argument
eth1: Invalid argument
vlan1: Setting MAC address to 00 1a 70 5a 92 0e.
SIOCGIFFLAGS: No such device
SIOCGIFFLAGS: No such device
SIOCGIFFLAGS: No such device
SIOCGIFFLAGS: No such device
ip_conntrack_pptp version 1.9 loaded
ip_nat_pptp version 1.5 loaded
Apply:submit_button=[Management] service=[management] sleep_time=[0] action=[4]
nvram_commit(): end

Team Bonding (using stickers!)

2009-12-23T22:34:00.014+05:30

We like to do things differently at LARE - here you can see us working together putting version stickers on lots of ATmega8s for some project that we just completed.
It's a "building the team spirit" activity - rather than playing games at some corporate picnic (corporate is too big a word for our - as yet a small organization!), we all take a break every now and then and spend time togehter on these little joys of life! (there were songs playing in the back ground!!)
This reminds me of my childhood.. used to love all those stickers.. In fact I still love stickers very much, both my home & my office desktop CPU Cabinets are covered with them!! (Deeksha, thank you for the stickers!)

Home Desktop:

Office Desktop:

buying, selling, merging, spinning-off and renaming

2009-11-29T22:15:00.001+05:30

We constantly hear of semiconductors companies being acquired by other semiconductor companies. For a student who has just entered the workforce, it might be a bit diffuclt for him/her to assimilated the whole scene and identify each player under various categories - micros, mempories, RF etc. The diagram prepared by the folks at EFT ON is a nice way to visualize whats been happening so far:

http://www.efton.sk/t0t1/semic_change.htm

Some amazing Embedded C programming Tips and Tricks

2009-10-11T00:11:00.007+05:30

Using macros to handle individual or groups of bit in SFRs easily:
Barr Code: Binary Literals in C

CRC:
CRC Implementation Code in C by Michael Barr

Will be updated as and when I come across new articles.

Who are we?

2009-05-08T01:35:00.006+05:30

Hi, I am Anurag Chugh. I work at LARE
LARE is an Indian company working in the field of embedded electronics.
Our website is located at www.lare.in.

Here is a short description of what we do:

UC Micro Systems (www.ucmicrosys.com)
LARE is a "Services Only" Company and is a subsidiary of UC Micro Systems (www.ucmicrosys.com). UC Micro Systems manufactures and sells various products - mostly development tools for electronics engineers involved in developing embedded systems. The UNIPro Universal Programmers are the most popular product series sold by UC Micro Systems in India.

LARE Learning Center
LARE provides corporate and academic training solutions in the field of electronics. We do so in two ways: either by carrying out courses at out Learning Centers or at the client's venue. Our first "Learning Center" was inaugurated in April 2009 at Belapur, New Mumbai, India. We have a lot of resources here , which the students can make use of to get hands on experience developing latest technologies being used in latest consumer and industrial electronics.
Through these "Learning Centers" we in intend to fill in the gaps in knowledge which the student has acquired at college.
At college, the student might learn what a capacitor is and how it looks on paper. But when the student actually enters professional life, he/she finds that there are a million kinds of capacitors in millions of packages with many different parameters other than just the capacitance value. A 10 microfarad capacitor might be made of tantalum in a Case B Surface Mount form rated at 16Volts or it might be cylinderical and a centimeter high with leads spaced 0.1 inches apart and rated at 25 Volts.
This tantalum capacitor might be used in a power supply section of a board sporting a multi-core IC with RISC microprocessor and a digital signal processor running linux playing a full-HD movie from the SD card on a 17" LCD TV. Well if you want to know how to select a single capacitor from amongst a million and how to go about using it in developing hardware and software for systems as simple as a wrist watch or a calculator to those as complex as the kind used in the cellphones, this is the place to come.

LARE Research Center
The Research Center provides design services and technical support to all internal departments of LARE and UC Micro Systems. It's like the brain - The Fountainhead if you may - behind all the activities carried out at LARE. Whether its developing universal modular electronics blocks (UNIBlocks) for use in student projects/ professional prototypes or Hobbyist Kits (VishaKits) or even full fledged development tools (SDKs for UC Micro Systems) - Research Center does it all.

LARE Design Services
LARE Design Services provides solutions to develop products for external clients. The activities carried out at "Design Services" are similar to those at "Research Center" but catering to external clients. The main theme here is "System Integration". If you want the legacy equipment in you company to be updated using latest technologies like Ethernet, WiFi, Bluetooth then this is the place to come to. It doesn't matter what your product involve : LCDs, stepper motors, GPS, any kind of sensor - smoke or oxygen, hall effect or dirt, load cell or colour - we can definitely come up with a design as per your needs. Currently we are serving only Indian clients.

LARE Resource Center
Takes care of the sales and marketing of LARE Services and UC Micro Systems Products.
It also provides Technical Support to clients who have opted to buy services and products from us.

Visha Electronics Corporation (www.vishaworld.com)
Visha Electronics is a very well known components distributor based in Mumbai, India. Visha Electronics aids the LARE Resource Center in its Sales and Marketing activities.

Address:	1st Floor, Kalpana Building, 349 Lamington Road, Opp. Police Station, Mumbai 400 007, INDIA
Phone:	+91 22 23862650 +91 22 23862622
Fax:	+91 22 23884401
Email:	info@vishaworld.com