I am exhibiting at the World Maker Faire (September 23 – September 24)

August 24, 2017

I haven’t been actively maintaining my blog these days. I recently moved to the Buffalo, New York area and settling down. I am willing to keep up with my blog posts. I have some great news to share with my readers.

My brother and I are going to be exhibiting at the World Maker Faire on September 23rd and 24th, 2017 in New York City. We are going to be showing off a DIY Personal Health Dashboard.  We have been working on a visual aid that motivates one to stay physically active.


I plan to share my progress of our dashboard through the different stages.


We look forward to seeing you there.


Flashing an Arduino Mega 2560 with firmware stored on a micro SD card

May 31, 2015

I was trying to determine if it is possible to remotely flash firmware on an ATmega2560 microcontroller using a micro SD card. I came across this repository of an ATmega2560 bootloader that flashes the microcontroller’s flash memory when a particular address on the EEPROM (Address: 0x1FF)  is set to the value ‘0xF0’.

When the microcontroller is reset, if the EEPROM value(at address ‘0x1FF’) is set to ‘0xF0’, the bootloader looks for a file ‘firmware.bin’ on the SD card and flashes the microcontroller with the new firmware.


Adafruit Music Maker shield mounted on the Arduino Mega2560

I had to make minor modifications to make use of this bootloader. I changed the Chip Select pin number of the micro SD Card (there are tutorials that explain how SD cards are interfaced to microcontrollers) in the macro definition to match that of the Adafruit Music Maker shield (the micro SD holder’s chip select pin is connected to Digital Pin 4 of the Arduino. This corresponds to pin 5, PORTG on the ATmega2560. Source: Arduino Mega 2560 schematic).

In the file asmfunc.S, I changed the CS pin to pin 5 on PORTG:

I also had to change the pin number of the LED used to indicate the progress of flashing the microcontroller by the bootloader.

After recompiling the bootloader’s source files, I flashed the new bootloader using AVR ISP MK II. I also had to make sure that the BOOTRST fuse was set in the ATmega2560’s fuse settings.


ATmega2560 fuse settings

I compiled an LED blinking sketch and converted it into a binary file by executing the following command:

Note: The Arduino IDE compiles and stores its hex files in a temporary directory. In order to save the hex file upon compilation, edit the IDE preferences after closing the IDE. The preferences text file can be located at File–>Preferences


Arduino IDE preferences

A line build.path has to be added to the preferences file. I included the path where the output of the compiled Arduino sketch would be located. I used Atmel Studio to convert the Arduino sketch’s hex file to a binary file (the avr-objcopy command shown in the above code snippet). I copied the binary file onto a micro SD card and inserted into the music maker shield’s micro SD card holder.

I made use of this sketch to set the value ‘0xF0’ at the address ‘0x1FF’. Upon reset, the bootloader flashed the microcontroller with the binary file located on the SD card.

Things to investigate:

1) When I was looking for a bootloader that would flash a microcontroller from an SD card, I read about problems encountered by others. I found out that people had problems using certain types of micro SD cards. I did have a hard time getting the bootloader working but it was due to the fact that I did not set the BOOTRST fuse.

Do let me know if you have used this bootloader or something similar in the past.

Starting to program with your FreeDuino

November 16, 2009

For those who aren’t aware of Arduino boards, I am posting some basic information.

Arduino is an open source hardware provided with a Free IDE. The information about Arduino Boards are available at :


As a beginner, you might not be proficient in soldering circuits and debugging them.  It is better to purchase an Arduino board that is readily available in the market.

If you are from India, one of the vendors in India for the Arduino boards is :


They are based in Pune and they are quite helpful in shipping the material and assisting you with all the necessary information. Their sales team was quick enough to answer to my queries.

In my opinion, 600INR  is worth spending on this board.

You may download the IDE from :


However, there are lots of constraints with this software like:

If you are using a low bandwidth connection, you may feel that the file size is quite large ( 80 MB).

It requires a Java run time engine ( that was not a problem for me at least ). Imagine a high school kid or a someone who is very new to computers and electronics trying to start with Arduino.  These minute details need some attention!

However, an Arduino is the best way to start your hobby.

When you power your board using a 9V adaptor, the Red LED on your board, starts blinking. It would have been loaded with the LED program already and it shows that your board is in a good condition.

When you launch the arduino.exe file, a screen appears before you as shown in the figure below:


I found the IDE to be user friendly. When I started learning MPLab (PIC Microcontrollers) and AVR Studio ( AVR microcontrollers), they were complex enough to make me lose interest in learning them.

There are good examples available along with this IDE. You may access them as shown in the figure below:

Launching an application

This opens up a LED Blinking program in a new window.

LED blinking

The actual code for the program is available at the link highlighted in the picture.


int ledPin =  13;
The 13th pin is where your LED is connected. So it is assigned to a variable ledPin.
void setup()   {

pinMode(ledPin, OUTPUT);
The 13th Pin is configured as an output pin.
void loop() — This is where the body of the program is written.  
digitalWrite(ledPin, HIGH);
A signal “1”is sent to the 13th pin.
There are code libraries which generate delay in milliseconds when you enter an integer value in the delay(integer) function. Here the delay is for 1000 ms.
digitalWrite(ledPin, LOW);
A signal “0”is sent to the 13th pin.
A delay for another 1000 ms.
Hence your LED switches on and off every second.
Any code needs to be compiled before you run it. You can compile this code by clicking the button : Play
Now when your compiling is done,  a “Done compiling” message appears below your window.
Press “Ctrl+U”, The LED connected to your 13th pin starts blinking!