I have a single ESC that continuously beeps while plugged in to my computer via USB and using Mission Planner. I can calibrate the ESC's, calibrate the radio, make changes in Mission Planner, etc,etc. but that one ESC always beeps. When my model is powered up via the flight battery that particular ESC works (and sounds) normal. This nuisance just started since updating to FW 2.9.1
I have only hovered the model since this issue started but it is rock solid in the air. I can't figure out why just one ESC continuously beeps but only when connected to Mission Planner. I have calibrated the throttle with the trim down, trim up, trim middle-no help.
DJI 30 amp Opto ESC's
APM 2.5 with 2.9.1
SunnySky V2216 800kv motors
I'd bet that the ESC which beeps, is the one that usually is supplying the APM with electricity.
When you connect the USB to the APM, you're feeding the APM with +5 volts, the same voltage
will travel back to the ESC and hence booting it up. But since it doesn't have the required voltage
from the battery it starts beeping out errorcodes.
Solution: Remove the cable which feeds your APM when you are using USB.