I've come to discover that we may be triggering our PPM pulse samples based on the wrong edge (rising vs. falling).
Can anyone post PPM sum traces from their Rx(s)? I'm looking for if the signal is positive (normally low) or inverted (normally high). These FrSky captures (below) are "inverted," at least for our purposes (purple, green, and orange lines). The individual channels shown in the first capture would be considered positive, I believe.
Most of the captures I've found online from Rxs with PPM sum output are also inverted (including the Ardu/Paparazzi PPM encoder). The current AQ code is triggering based on a positive signal. When I invert it in the code, the PPM decoding of my FrSky Rxs improves significantly (way fewer invalid pulses and no dropped frames). It does work fine the current way, but the results are much cleaner when triggering on the correct edge. And it does resolve the issue I was having with the 27ms FrSky firmware.
Thanks,
-Max