Missing ESC Telemetry Amp Data Causing Motor Failure Warning

aluna · July 30, 2025, 6:03pm

On take-off I am getting a preflight motor failure warning. When I disconnect my ESC telemetry data I do not get this. My ESC telemetry data using Dshot1200 (mamba f55_128k bl32) does not include motor current and I assume this has something to do with the problem. Is it possible to disable motor failure detection using individual motor currents? I believe there was a similar issue [Bug] False motor failure detected with Dshot telemetry · Issue #23734 · PX4/PX4-Autopilot · GitHub recently. I am using PX4 1.15.4 and PX4_FMU_V6C.

dakejahl · July 30, 2025, 6:09pm

DShot1200 is unreliable and has since been removed. I recommend reducing to DShot600

aluna · July 30, 2025, 6:27pm

Thanks for the advice. This makes sense. I have just checked another setup I have using a Pacer P50A ESC which also does not have motor current in its telemetry and this does not give me the failure warning. Tomorrow I will try DShot600.

aluna · July 31, 2025, 5:59pm

I have now tried DShot600 and there is no differrence. I still get the motor failure warning on take off. The live ESC telemetry data for motor current in QGC shows spurious values while the log shows no values at all.

dakejahl · July 31, 2025, 6:34pm

Which serial port are you using for ESC telem? Can you share a log?

aluna · July 31, 2025, 7:02pm

I am using GPS2. Here is the log using DShot600.

dakejahl · July 31, 2025, 7:50pm

This log does not contain the issue. Can you please share a log that captures the issue?

aluna · July 31, 2025, 8:39pm

The Failsafe Flags show the fd Motor Failure warning - thats all. The spurious motor amp values I am seeing in QGC do not appear to be logged anywhere however, the QGC motor rpm appear correct.

dakejahl · July 31, 2025, 9:26pm

It looks like the issue is that only 1 ESC is reporting valid current values. The other ESCs are reporting near 0, which triggers this failsafe:

github.com/PX4/PX4-Autopilot

src/modules/commander/failure_detector/FailureDetector.cpp

0cddd3dfb


      
          			// Check if ESC current is too low
          			if (cur_esc_report.esc_current > FLT_EPSILON) {
          				_motor_failure_esc_has_current[i_esc] = true;
          			}
          
          			if (_motor_failure_esc_has_current[i_esc]) {
          				float esc_throttle = 0.f;
          
          				if (PX4_ISFINITE(actuator_motors.control[i_esc])) {
          					esc_throttle = fabsf(actuator_motors.control[i_esc]);
          				}
          
          				const bool throttle_above_threshold = esc_throttle > _param_fd_motor_throttle_thres.get();
          				const bool current_too_low = cur_esc_report.esc_current < esc_throttle *
          							     _param_fd_motor_current2throttle_thres.get();
          
          				if (throttle_above_threshold && current_too_low && !esc_timed_out) {
          					if (_motor_failure_undercurrent_start_time[i_esc] == 0) {
          						_motor_failure_undercurrent_start_time[i_esc] = time_now;
          					}

This file has been truncated. show original

dakejahl · July 31, 2025, 9:27pm

I would try adjusting the parameter FD_ACT_MOT_C2T

aluna · August 1, 2025, 5:35am

Thank you for you excellent help. I was looking at the log which was recorded when using DShot1200 which did’nt log motor currents. I have set FD_ACT_MOT_C2T = 0 and using DShot600 and the warning has stopped. Many thanks again !

system · August 8, 2025, 5:35am

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Missing ESC Telemetry Amp Data Causing Motor Failure Warning

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