Hi! I have a pixracer board here, I have been using it with Arduplane 3.7.x and Arducopter firmware for a year. and recently, I tried updating it with the ArduPlane 3.8.1. Everything was setup properly, but when I tried powering it with my lipo pack, the esc does not seem to recognize the cells, no beeps. Normally the flight controller will send some PWM values to the esc so it will know how many cells are there in the lipo. And since no beeps where emitted by the motor, I can arm the plane but the motor has no response.. I removed the lipo, plugged the Pixracer to my laptop to power the pixracer, and immediately the motor beeped, then I plugged in the lipo, and yes it armed and the motor ran.. Again, I removed the usb cable and lipo, tried powering the pixracer with a lipo only, the issue is back,no beeps from the motor.. I tried reverting the Pixracer to Arduplane 3.7.1 and throttle works..motor beeps normally. but then after I upgrade to 3.8.1 the problem is back.. For now I replaced the pixacer on my plane with a pixhawk lite, flashed it with 3.8.1 and it works flawlessly. Perhaps some bugs with the Pixracer when running AP3.8.1?