Hello there, The Pololu 3pi is a fantastic robot that I unfortunately didn’t get to work with very long until it apparently broke. I was thinking of adding a i2C real time clock to the pololu 3pi to print out the actual time into the LCD screen, this seemed like a cool little project to do. The pololu 3 pi has some pins next to the battery holders labeled PD0, PD1, PC6, PB3, etc. all around the board, I assume that these are the ATmega’s I/O pins. The library I was using to control the real time clock allowed for any pins to be used as SDA and SCL, so I deided to just put the clock’s SDA and SCL in any pin at all, then I could just tell the library to use those pins for i2C. So I set out in soldering the clock’s VCC, GND to corresponding pins. And I soldered SDA and SCL to PC6 and PB3, damaging two solder pads in the process, unfortunately.
The second I turned the 3pi on, from memory I recall that that LCD showed the title screen, but it was extremely dim, then it turned off. I programmed it to beep a couple times when turned on, as well, it did not beep. I panicked and immediately turned it off, and desoldered the clock’s pins to see what in the world had happened to my 3pi.
I connected my Sparkfun avrdude USBtiny into the Pololu, which had worked before (Note: The USBtiny can provide it’s own power to a board). The LCD lit up finely, but did not do anything, the top row just filled with black boxes, I was concerned now. I ran avrdude with Atmel Studio to check and see if the IC’s devie signature was recognized, it was only a random string of numbers. I tried again, this time with the 3pi shut down as I conneced it, and when I connected it in, i boot up perfectly with no issues. Then, I disconnected the USBtiny from the board, the LCD was extremely dim again, I reset the board and it didn’t boot up at all. Some one please, help!