Building CubeSat is fun. It is more fun, if there are proper instruments. With our CubeSat debug tool it is possible to measure, disconnect or modify interconnection of any signal from standard 104 pin CubeSat connector. I2C bus pull-up resistor is missing? No problem, if you have common resistor with wire leads to plug it in. Is there some problem with signal allocation? The board probably needs to be modified, but it can be tested now by making correction on debug tool. Measurement of currents flowing from one board to another is also simple thanks to possibility of disconnecting path and insertion of ampermeter. There is also dual-channel USB converter with serial or parallel interface enabling communication of devices with PC.