PPM signal timings

Hi, I'm trying to feed PX4 with a PPM signal created in software, I can't get it work correctly because I can't find the timings needed.

For example,

1)PPM pulses must be active high or active low?

2)What is minimum and maximum duration of each pulse?

3) Must I provide a fixed number of channels or the board itself counts the available channels on PPM?

Thank you!

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Replies

  • Hey, did you manage to successfully accomplish this? And do you have any more information on this topic?

  • Hi, I resolved on my own, just for the curious ones:

    1) For PX4 is not important since it watches for the edges, however i used an active low configuration

    2) minimum and maximum duration of a ppm pulse is for PX4 between 200 and 600 us

    3) the board itself counts of many channels are present with a minimum of 5

    • Hi there, I am trying to do the same thing, I wonder if you mentioned ppm pulse between 200 and 600us is the Pulse duration (which is 1200us - 1900us usually) or the interval between 2 edges of Pulses?

      • Hi duc:

        I just intended that in order for the edge to be detected it is enough to set a value between 200 and 600 us. But this value is not the pwm pulse duration.

        The pwm pulse duration in ppm is accounted like this:

        PPM Signal:

        __| 400us |________________________| 400us |__________________|          |__________

           <---------------------------------------------------><----------------------------------------><------------------------------....

            PWM Channel 1 (1000us-1900us typ)     PWM Channel 2 (...)                   PWM Channel n

        • thanks, it works great for me!

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