Pololu 3pi robot acting highly unusually

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!


Why did you pick PC6 and PB3 on the 3pi to connect your external clock to? If you do not already know, PB3 is used for motor control and ICSP programming and PC6 for reset. You can find that information in the “Pin Assignment Tables” section of the 3pi user’s guide.

Can you post close-up pictures showing the expansion area on the 3pi, especially the damaged pads?

Does the your 3pi only work when you connect your USBtiny programmer to it? Can you remove the LCD from the 3pi and try loading one of the buzzer examples (e.g. buzzer1) from the Pololu AVR C/C++ library? Does the buzzer work? Can you also try loading the motors1 example?

- Amanda