I'm part of a robotics team in my highschool. We work on autonomous robots, which are driven with microcontrollers like the Arduino and "bare" Atmel chips.

Last year we were using a protocol called CAN. CAN is a bus which runs at 1Mbps and it is quite easy to connect devices together. (It's a bus ofc it is). BUT... it needs a terminator at the end, mostly 120 ohm.

Every year we are on a deadline and something broke on our current board and we needed to solder up a new one, but we couldn't find the 120 ohm terminator... ANYWHERE!

At end after searching for it in the workshop for 4h straight (12am- 4am) we finally found it, and soldered up the new board and guess what... it wasn't what we thought, the code was the problem.

After realizing the problem my teammate and I, in silence just stood up, packed our things and went home. Argh!