The most challenging part to the design and development of a power meter is certainly the packaging – or maybe it’s the programming, either way it’s actually not the instrumentation side of things. I think I’ve found a way to package the electronics out of the way and not interfere with the RF signal which was an issue with V2. I’m planning to move to the nRF51422 eventually but until then I’m using a hobbyist microcontroller board to speed development. The new board is to be mounted to the inside of the the chain ring side crank arm. The AP2 module will hang off behind the arm. This means there is no metal near the module to interfere with the signal. I still need to incorporate the battery. I might take the Rotor route and use the higher capacity cell rather than the 2032. Perhaps the 2477 cell.
The unrouted trace is a ground, there are multiple grounds and I’m avoiding ground loops.