Pixhawk 2.1, APM 3.5 and DJI E800 issue


We’re having issues with the DJI E800 propulsion system, it uses the 620S ESCs.

Copter 3.5 is set up correctly, sensors calibrated. Everything seems fine but the motors that don’t spin at the same RPM. Of course I tried to calibrate the ESCs but it seems to don’t work as for my T-Motor ESCs.

Flight mode is stabilized, raising the throttle one or two motors start to slow down progressively.

Also, after about one minute, the FC crashes.

Please watch this video and turn on subtitles to understand more: https://youtu.be/aQN3-HW242k

Could you please help me to solve this problem?

Thanks for the video. There’s a few things going on here, I’ll try to explain them all. The important thing to remember is that the flight controller doesn’t know that you’re just testing the copter on the ground - it assumes that it might be flying, so it attempts to control the attitude of the drone while on the ground. This has several effects:

  • It is trying to stabilize itself. This is why the motors slowly change speed by themselves - probably, the flight controller isn’t perfectly level, so the I term of the PID controller is winding up causing the drone to try harder and harder to correct its attitude.

  • As the drone tries to change its attitude, it begins to realize that the attitude is not responding to its motor commands. This is especially true when you give stick inputs. The crash detector uses a threshold of motor commands vs. attitude change to detect when the copter is crashed. This often leads to crash detection when testing on the ground, especially when you give stick inputs.

  • DJI ESCs are a bit strange, as they use a weird PWM range, have a ‘soft motor start’ function, and they cannot be calibrated. You must change the motor PWM outputs to match DJI’s specification. You do with with the MOT_PWM_MIN and MOT_PWM_MAX parameters. The DJI E2000 uses a PWM range of 1120-1920, but I don’t know if this is true for all of their propulsion systems. You may also need to play with MOT_SPIN_ARM and MOT_SPIN_MIN parameters. There’s a few posts about it on these forums.

Thanks Rick for your exhaustive answer. The drone is perfectly leveled so I rule out any issue about that matter.

I will look for 620S PWM range and eventually will post the solution here.

Thank you very much again for your support.


I had problems with some esc when it gave more power the drone was deseblilized, I would try other ESCs.

luck and regards