Next problem: PPM

So I want to use a PPM encoder for the PWM receiver I have.

No oscilloscope :frowning:

The PPM encoder I am using is based around the ATMEL ATMEGA328p AVR processor; design of the encoder is based on the Paparazzi PPM Encoder.

First, is there a change I can make in the PPM.cpp example to read inverted PPM signals? If I can see them, I know I need to reprogram the encoder.


This encoder should work with Navio+ right away. Are you experiencing any issues?

Doesn’t work.

In Mission Planner, when I do the radio config - no movement from movement of the sticks. I can see that the PPM encoder is working , because when I move the throttle channel the LED on the encoder blinks slower or faster based on where the throttle is. But nothing in Mission Planner.

Connections double checked, power to encoder is separate, etc., etc.

PPM.cpp example produces only zeros for values for the channels…


Also, remember, I have the Navio RAW

I also had some problems initially with my PPM decoder that I was able to solve so I thought I would pass those along.

  1. Check the voltage output of the PPM encoder signal. The Navio (original) is setup for a 5V PPM input signal but mine was only 3.3V so I had to remove a resistor in the voltage divider to get it to work.

  2. Make sure the ‘Options’ in the header are set for your system. This can be a bit tricky without an o-scope. Some PPM encoders output 8 channels no matter what, but mine only outputs as many channels as signals were going into the encoder. The ‘ppmSyncLength’ also was different for my encoder. The default is 4000, mine was 7000.

Hope this helps.

Tim, do you have a voltmeter (multimeter)? If yes, could you please measure the PPM output of the receiver?

Oh yes, Navio Raw will not work with Paparazzi derived designs as they are 3.3v. This is fixed in Navio+. Please remove R8 on the bottom of the board to use with 3.3V logic. After you remove it do not connect 5V PPM there as it will damage the RPi.

I’ll give it a try.


Works fine now. Thanks. But I think I am going to need a Navio+, really, so I am on the same page as everybody else (since the Navio+ outputs raw data for RTKLIB). How much is my NavioRAW trade-in worth? :smiley: