Tricopter - Pixhawk 2.4.8 latest version

Hello everyone.

I´m building a Y600 tricopter using pixhawk 2.4.8
the first issue is that following this:
If I connect the YAW servo to port #7 of pixhawk nothing works, the only way to have YAW servo responding to the sticker was by wiring it to Taranis receiver port #4.

What is currently happening is that the quad tries to spin, if I correct it on the YAW sticker it gets stable for sometime (few seconds then it again tries to spin, Motor rotation is correct otherwise I would not be able to fly at all.
Flightmode is Stabilize, but Acro does the same (both without GPS for now)

  • Why can´t I use port 7 from the pixhawk as described on the documentation ?
  • can this issue of not using port 7 from the FC causing this problem ?

Any clue ?

check that servo7_function parameter is set to 39, and also make sure that the servo rail has power to it. You will need a 5V bec. DO NOT POWER THE SERVO FROM THE RECEIVER as this will pull too much current from the autopilot.

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Hi James,

I confirmed this si configured to 39 correctly. I have the power module giving power to the pixhawk, is this enough ? Please consider my ESCs are providing the power supply with the BEC.

I have motors on 1,2 and 4, and if I put the servo on 7 nothing happens.

What else you think I could check ?

Many thanks

The power module doesn’t feed the servo rail: servo rail needs to be supplied separately.
If your esc’s have a bec in them (some do, most don’t anymore) then that might suffice but you’ll need to check whether it is sufficient. Often bec on esc’s have a 1A limit, which is probably not enough. I always power the servo rail separately and strongly recommend it. Have a read here: it may help explain.

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I have a separated BEC and its an easy test, worth a try !

I come back to this tomorrow with the result!

Super thanks

frame Tri. Servo7_function 39 . Servo has separated BEC , but dont work. All same Fernando_Labombarda

I’ll try to set up a test over the next few days (my tri doesn’t currently have an autopilot in it), but in the mean time can @Fernando_Labombarda and @damianden please confirm that you haven’t uploaded an old param file from before AC3.5, and also can you please post a log file?

Hi James,

sorry for the delay, I only had the chance to look into this now.
servo7_function is 39 as expected.
I don´t think I have uploaded any old param file James.

This is weird, My board hasn´t generated any log. the APM folder on the card is empty, I checked the settings and the LOG BITMASK is properly configured.

What could possible be wrong ?


Just pasting a link to Dropbox or google drive is easiest.



For some reason the board is not generating log files, SD Card has the APM folder empty, but log bitmask looks correct.
Any idea ?

Just to check: the copter is arming correctly, right?
Anyway, could be an SD card issue, but try with log disarmed to 1 (starts logging when powered on), and see if that gives a different result. Also, if you could save your parameters to a file and upload those it will give me something to look at.

For some reason the board is not generating log files, SD Card has the APM
folder empty, but log bitmask looks correct.
Any idea ?

Arming checks enabled?

What’s LOG_BACKEND_TYPE set to?

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