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Solved: Pixhawk APM 3.2 + Throttle Anomaly (Possible mistake Tx, Rx, PPM encoder or Pixhawk RCIN logic)

Posted by Eva on February 10, 2015 at 2:25am

Hello!

In stabilize mode my drone could not take off (radio thr stick was over mid position, but drone "jumped"): please look at video attached.

Video: http://youtu.be/b9PoUtGiBQ0

I will attach log file: LOG

If You see the RCIN and RCOU parameters, then You can see, that for some reason throttle signals falls randomly to minimum, that explains the "jumping" in stabilize mode.

TEST_FAIL.mov

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Tags: 3dr, c3, ppm, pixhawk, thrin, throut, encoder
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  • Eva February 10, 2015 at 11:28am

    Hi again.

    From logfile I can see why drone suddenly falls - throttle signal is "lost". Failsafe is set to 925, but here I see, that it is just going to minimum. Look picture and logfile on 8 min - there is 3 distinct throttle falls.


    I do not know, if I interpreted parameters from logfile correctly:
    CTUN - ThrOut (it should be final throttle which is given to motor controllers as output)
    CTUN - ThrIn    (it should be (?) signal, which comes from transmitter's receiver, scaled from 0 - 1000)
    RCIN - C3         (should be throttle in input signal from radio receiver via PPM encoder -> PPM signal)


    So

    1) maybe mistake is on TX side
    2) Maybe mistake is on RX side
    3) Maybe mistake is with 3DR PPM encoder
    4) Maybe mistake is with Pixhawk's RCIN port or logic ...?

    If someone experienced this problem, then let me know.


    Logfile of this flight is here: logfile3701931993?profile=original

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    • Eva > Eva February 12, 2015 at 12:04am

      Case closed.

      Fourtunately mistake was on Tx-Rx not firmware nor PPM encoder <-> firmware

      I made one more flight and measured Rx values directly and this error occured already there.

      Look at the pic: Upper - log from Pixhawk C3 (throttle signal input), excel - measurements directly from Rx (Pwm -> active duty cycle -> ticks).

      3702547606?profile=original

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