Pixhawk2 no servo output

I’m having problems getting any output to the servos or ESC. I suspect it’s a arming error but can’t see anything in the logs.

[MAV 001:1] ArduPlane V3.8.0beta2 (5baf37f7) 
[MAV 001:1] PX4: 3df5644c NuttX: be6ff61a 
[MAV 001:1] PX4v2 00210033 34355111 38393730 
[MAV 001:1] u-blox 0 HW: 00080000 SW: EXT CORE 3.01 (107900) 
[MAV 001:1] EKF2 IMU1 is using GPS 
[MAV 001:1] EKF2 IMU0 is using GPS 
[MAV 001:1] Throttle armed 

I’ve changed the ARMING_CHECK to 0 and tried again but no luck. All mandatory setup done. The Edison companion board is running APSync which works well to connect to APM Planner over wifi. I’ve added tape to the Pixhawk Cube and changed SERVO5_FUNCTION=33, SERVO1_FUNCTION=0 as per the Service Bulletin. Currently using ArduPlane 3.8.0beta2 but it does not work with 3.7.1 either.

Is there something that I’ve forgotten?


Could it be an issue with safety switch?

Hi Oliver,

I’ve tried both the safety switch which comes with the Pixhawk2 and the Here+ switch. Both flash red 4 in a row then blank. If I press and hold either switch it goes solid red and the servo twitch. The servos don’t move but they do change pitch ever-so-slightly when I move the transmitter sticks.

All the servos, ESC and batteries work with the Pixhawk1.

Today I’ve reset the parameters, reloaded the firmware and gone through all the mandatory setup in APM Planner also switched out the ESC and servos for other known working ones. Still the same problem.

Next I’m going to try removing the Edison. If that does not work, I’ll try QGroundControl.

If that does not work, I’ll go back to the Pixhawk1 since I’m loosing the will to live!

I’ve taken the Edison out but now the ESC just beeps indicating “Throttle is not in the lowest position”. Radio is calibrated and I’ve tried two FrSky x4r receivers and a FlySky i6 receiver, all with the beeping. Pixhawk2 has been reset again and recalibrated.

I’m going to rebuild with the Pixhawk1 so I can actually fly this plane and wait for Pixhawk2 inspiration.


Do servos resist movement when you apply force?

It was weird, the servos did resist movement but only one way.

Anyway, found the issue…

Very late last night I replaced the Pixhawk2 with a known working Pixhawk1. This plane has 4 servos and none worked with the Pixhawk2 but 3 worked with the Pixhawk1. I changed the dead servo for a new one but that did not work either. Tested the servo extension cable and it had a short between signal and gnd so replaced that (took ages because it was embedded in the EPO) and all servos then worked fine.

Switched the Pixhawk2 back in and all is working! Yay!

So, conclusion is… The pixhawk1 is more tolerant of bad connections than the pixhawk2. Also the pixhawk2 seems to carry the symptoms over between reboots - I changed the servos and bypassed the extension cable yesterday morning and still had the same symptoms.

It would be interesting to know what would happen if a short happened during flight - maybe the pixhawk2 would gracefully glide to earth where the pixhawk1 would try to control the remaining servos and land, err, more dramatically…