Build in HMC5883L compass/magnetometer is very nice feature of Flip32+ flight controller. Too bad it’s not always working like expected and there is a time, when one have to replace it by external device, positioned as far away from power cables as possible.
I’ve encountered that specific problem two weeks ago when I’ve discovered the reason (or at least I think I discovered) why Position Hold and Return To Home GPS assisted flight modes on my Flip32 and Cleanflight were not working. Or rather were working only sometimes, usually when quadcopter was positioned to the north, north east. On any other case, huge overshoots, going in totally different direction than expected. GPS was more less useless. Finally, during one one flight I kept attention to compass heading displayed on OSD. On the ground, heading was correct. After take off, it was drifting to east. Always east. With that data I’ve concluded: Flip32+ built in compass is too close to power cables and when motors are running magnetic field makes compass readings unreliable. Solution: move compass further away from power cables. But with compass already on PCB it was rather impossible. So the only real solution is: disable internal compass and use external HMC5883L connected over I2C bus.
Unfortunately, there is no software solution to disable onboard HMC5883L or just connect external one without physically disabling internal. They both use the same I2C address and that would not work. Internet says that you should cut SDA and SCL lines with a knife. Hmm… cutting PCB is not easy, and those traces are small. Easy to cut something else. If you have hot air station you can just remove compass by unsoldering it. If you don’t, I have different solution: remove it by force.
I used Olfa knife and just hard pressed it from one side. It went off pretty easily. Soldering pads on it are small, and solder itself was not very good (see missing USB port?). So it just popped. Problem solved. Board still works, there is not internal magnetometer and external can be connected to I2C bus with ease. But that will happen tomorrow, when new parts should arrive…