Hello !

I've been trying to understand the functionning of the PPM and PWM signals for some days in order to write an algorithm that can generate them via a an arduino . However , I can't find suitable informations about the communication protocol used by RC transmitters . 
How is the receiver able to differentiate between the channels when it receive a PPM signal ? 
How am I supposed to send a PPM signal that maintains the motors running if it's a serie of 20ms pulses ? 

Sorry if those looks like dumb questions but I'm trying to understand RC control as much as I can and those issues are really slowing me .
Also , if you have any useful links explaining with accuracy PPM signals (for multicopters use only) , I would gladly read it . (It can be in english , french or spanish , I don't mind)

Thanks in advance!

Hi, such algorithms are part of the firmwares used in the mini quads like betaflight, cleanflight, etc. Since those projects are open source and available on GitHub, you can read through the code to see how they were implemented.

PPM combines several PWM signals into one. Each channel is one of those signals. The first position of the PPM pulse will be channel 1 and so on.

As always Oscar has covered this in detail: https://oscarliang.com/pwm-ppm-difference-conversion/
And a nice PWM to PPM converter: https://oscarliang.com/build-pwm-ppm-con...-receiver/

Because PPM can be transmitted over a single wire (well 2 with a ground reference) an audio cable is a great medium. Hence, most radios have an audio (trainer) jack in the back that accepts PPM. Modify that DIY arduino project to send pre-set values to the PPM routine and plug it in a radio configured as a trainer slave. Chances are you will see your values mapped to the channels preserving the original order.