POC plugin that controls an RC transmitter

I want to use VCV Rack as a DSP workbench to try out some ideas. And… wow… I am loving it.

Here’s my first attempt at a plugin. All it does is generate a PPM signal. But, if you plug the audio out into an RC airplane transmitter, you could potentially fly an airplane with it:

I’ll need to clean up the signal to hopefully get rid of that jitter. But, yeah, this is going to be fun.


That’s cool. Can’t see the jitter in this video. Where’s it coming from?

yeah, the servos should be still, but you can hear them all constantly adjusting in the video. You can see it at 0:34. The movement should be smooth and then it should hold still, but it doesn’t.

The servo position is determined by a periodic signal that is 22.5ms long. Inside that signal there are 8 pulses that determine servo positions for 8 channels. Position is set by how long you hold a pulse high. 0.7ms is full left, 1.5ms is full right. So, say you hold the pulse for channel 1 high for 1.1ms the servo should hold steady in the middle. My guess is the pulse isn’t consistently staying high for 1.1ms.

And… I just looked at my code…I am literally just counting each time “process” is called instead of adjusting the phase based on sampleTime. doh! I bet that is the problem.

question! How does sampleTime work? is it a delta between the time the sample began and the time “process” was called, or is it literally just a counter? I guess I should ask,is there a writeup somewhere that explains timing? I looked for a few hours and couldn’t find a good explanation. thanks!

I’ve been led to believe it’s a delta. But lightly loaded I wouldn’t expect vcv to ever miss samples. Do you know about the submarine storage scope? It’s awfully handy.


wow, yeah, didn’t know about the submarine plugins but they look great! including that scope. thanks!

And if you ever need an FFT freq analyzer, Bogaudio Analyzer XL.