Additional VOXL 2 PWM ouputs?

maddyr13

I am trying to attach an additional servo to my m500 flying on VOXL 2. I am using the PX4 v1.14 parameters as specified in the voxl2_io_enable_pwm.params file. When I visit the PX4 website explaining the parameters available for the drone, it is clear that there are only 4 PWM output enabling parameters defined for the VOXL 2.

I know that I will have to attach my servo to the PWM breakout board utilizing a battery eliminator circuit, so at this stage I believe validating my setup is dependent on the support being offered to the VOXL 2.

Are there any updates as to when VOXL 2 plans to support additional PWM outputs beyond the four necessary to fly the drone itself? If there are no plans to do so, I will have to roll back to VOXL 1 where I have previously tested this setup and proven it works.

rdjarvis

@maddyr13, we are using the same VOXL2 IO board to run a 3rd party 4n1 ESC....Without great success. Did you have to update the firmware in order to get the IO to register the motors in Qgrnd?

Alex Kushleyev

@rdjarvis and @maddyr13

We have a pending update for voxl2 io board with a few fixes and it unlocks all 8 pwm channels. We are testing it internally and another forum user has successfully been flying with the new changes. Please see this post with detailed instructions and discussion : https://forum.modalai.com/topic/2446/connecting-i2c-device-on-voxl2/20 (my post on March 19). Please note the user had a crash but it was not related to voxl2_io performance, as discussed in that thread.

This requires to build PX4 from a test branch. If you are unable to do it, i can provide an updated .deb for you to test.

If the instructions from that post are unclear, please let me know. We will post official instructions once the update is formally released.

Alex

rdjarvis

@Alex-Kushleyev Hey Alex, Thanks!!

maddyr13

@Alex-Kushleyev Thank you!

maddyr13

@Alex-Kushleyev Actually, do you have the updated .deb file available that I could use?

Alex Kushleyev

@maddyr13 , sure, here you go : link

I built it using the voxl2-io-cleanup branch, which has latest from voxl-dev with added voxl2 io updates.

maddyr13

@Alex-Kushleyev Great, thank you! I was able to update the drone and see the increased number of PWM outputs. However, when I flew the drone the motors got incredibly hot after a very short flight, which they had not done on previous flights prior to updating. Do you happen to know of any other changes made with this update that may have caused this?

Alex Kushleyev

@maddyr13

besides enabling 4 additional channels, the changes included:

introduce new UART message between PX4 and M0065 board to allow specifying output pulse with high resolution (previously limited to only command range of 0-800 which was remapped to 1-2ms)
change the output pulse to OneShot, which means for every command from Flight Controller, there is only one PWM pulse (per channel) generated. This synchronizes the PWM output to Flight Controller update cycle and reduces total delay between FC and ESCs.
there was a bug in case of SBUS input was used, the output PWM rate was reduced to only 100hz (normally about 400hz using 1-2ms pulse, which is a limitation of the pulse width, since flight controller update loop is 800hz).

I am curious if you were using SBUS input into M0065 before for your RC, in which case the pwm update rate was reduce to only 100hz.

Change to OneShot should not have effect on the pulse width, only the delay of it. It is possible that with new firmware, the ESCs are getting updates at higher rate, which could mean that if there is high frequency noise (picked up by gyro from propeller vibrations), the ESCs are now receiving more noisy commands, which would cause the motors to heat up more.

If you have the PX4 logs from before the M0065 firmware change, you can take a look and see if gyro was picking up a lot of noise (more than 5-10 deg/s is considered more than normal). Additionally you can check the noise in the actuator outputs.

Are you still using m500 frame? did you modify it in any way? maybe VOXL2 needs more vibration insulation. Also, what you could do is restore the original M0065 firmware, use unmodified PX4 and compare results again (making sure to save the logs).

Also, did you go through the ESC calibration and updated the PX4 actuator ranges, as instructed, after uploading the new M0065 firmware?

Alex