Getting the PPM encoder working - How To:


I've spent the last 2 odd hours trying to get the Spektrum receiver to work with the PPM input with no luck :( I am trying to gather up bits so I can do a clear "how to" for this as it is all rather disjointed.

I've read the wiki: and it has helped nothing. Not much to go by and the user comments are somewhat disjointed.

I've read other people's post (pleas for help) which seem to have random success.

I've read Sam's blog:

  • I have a spektrum satellite receiver (which is bound)
  • I have the Spektrum PPM adapter. 
  • I've bridged the PPM->CH5 on the back of my APM2
  • All the radio channels show min values. If I don't connect the adapter they show blank so I assume it's getting some data.
  • Any movement of the sticks shows nothing. Everything still sits at 900.

I know I'm close because it is getting some data but it's not working :( 

Any help please? Anyone used the Spektrum adapter on the APM2?



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  • Developer

    Ok, here is the deal.

    - Spektrum satellites output servo channel data as a slightly non standard serial data stream.

    - Spektrum adapter, is not a Spektrum to PPM converter. It is just a 5V <-> 3.3V converter for the Spektrum satellite.

    On APM1 there is a custom firmware for the 328p chip so that it can understand the Spektrum serial data.

    At the moment, there is no custom Spektrum firmware for the APM2. The old APM1 custom firmware would have to be completely rewritten, since the new 32U2 chip also has to support the Arduino USB bootloader at the same time.

  • Anyone used the Spektrum adapter on the APM2?

    It's known that the spectrum adapter does not work with APM2. This is because the entire FTDI and PPM encoder are now done on a single chip and thus the code is entirely different.

    Info on APM2.0 PPM 

    This is why it won't work.

This reply was deleted.


Shivchand Jaysaval liked Shivchand Jaysaval's profile
Aug 25