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SumPPM problem with 2.40b6 ?
  • davidm
    I'm using GUI / Firmware 2.40b6, and my receiver is configured in CPPM (FrSky with 27ms period). My Flight controller (APM2.5) decode perfectly my receiver SumPPM signal, but I have a strange behaviour with this firmware.
    SumPPM signal is connected to RxR.
    In "RC settings" tab :
    - mode is set to "Sum-PPM"
    - PITCH has a virtual channel (VIRT_CH_6 in my case)
    - CMD has a virtual channel (VIRT_CH_7 in my case)
    - FC_ROLL is set to EXT_ROLL - PWM
    - FC_PITCH is set to EXT_PITCH - PWM

    In this configuration, without any change on my transmitter, my gimbal pitch has sometimes sudden moves with a quick green led flash on my board. If I set PITCH to "no input", sudden moves disappear.
    When my command switch is in the middle/high position, "Command Assignment" display a value around 1500/2000, but regularly, this box is quickly cleared (get black) with a quick green led flash on my board.

    It's like sometimes SumPPM signal is not well decoded.
    I don't have any I2C errors.
  • Garug
    Sounds like you have a some problem on the PPM signal, how does it look on Realtime data?

    APM2.5 might have some filtering that mask this problem.

    Have you tried the LPF on RC Settings, I currently use 3 and receive all mentioned information over Sum.PPM ok.
  • Garug
    3 seems to be the smallest LPF value that is accepted. 0 can be sent, but when reading back it is 3.
  • davidm
    With a low LPF value (3), my gimbal has bigger sudden move, with bigger LPF value (9/10), sudden move are smaller. But this only mask the problem. At this point I don't know if the problem cames from my receiver (seems strange because I don't have any problem with my flight controller), or something else.
    In realtime data, value are displayed correctly, but regularly, values are quickly cleared. So there's a problem, but I don't know what.
  • Garug
    Mine frame rate is currently 22.5 ms, but I do not think this should affect, I am thinking using even shorter frame-rate to improve FC data performance.

    Have you connected/shared the same PPM to APM and BaseCam? if you disconnect it from APM, will it improve the situation? It could be some level or grounding problem.

    Did your current system work ok with 2.3?
  • davidm
    Yes PPM is shared between PPM and APM, I didn't made a test with APM disconned, I'll make a try.
    For grounding, problem, the only ground connected is the one with the power cable (so only one ground cable), the other cables connected are only signal cable.

    I couldn't make any test with 2.3, because in my previous system, I needed VIRT_CH_8, and it wasn't possible to choose it with GUI 2.3, but my system was working fine with 2.2.
    Next step :
    - Test with CMD not assigned
    - Test with CMD assigned to another channel
    - Test with FC_ROLL / FC_PITCH not connected
    - Test with APM not connected
    - Display PPM signal with an arduino, to check if there're any signal problem

    I'll keep in touch
  • davidm
    Test with CMD not assigned : no change, small pitch movement
    Test with CMD assigned to another channel : no change, small pitch movement
    Test with FC_ROLL / FC_PITCH not connected : working fine
    Test with FC_ROLL connected, FC_PITCH not connected : no change, small pitch movement
    Test with FC_ROLL not connected, FC_PITCH connected : no change, small pitch movement

    So it seems there's a conflict between PPM Sum and Standard PWM Signal
  • Garug
    I did not think of that, that is good to know.
  • davidm
    I made a little test with an arduino, and I don't have any error, I manage to decode CMD channel in CPPM and I manage to decode in the same time the standard PWM coming from my flight controller (EXT_FC ROLL/PITCH).
    So there's no problem coming from my receiver / flight controller, pulse are correct.
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