PWM for GPIO control

[sdhin001]

Hello,
I have a weird need and want to see if it is possible.

I use the GPIO Input Triggers to play specific sequences as needed. The source of this signal is a Radio Control Transmitter that is able to output a true 3.3v Digital Signal that is on and off. It works great for this purpose. It is a direct connection from the RC Receiver to the Pi's GPIO.

Some radio control systems are only able to output a Pulse Width Modulation(PWM) signal. This cannot plug directly to the GPIO pin with Falcon Player and operate like I want.

With that said, is it possible to modify Falcon Player to measure a PWM signal and use it for input, instead of a constant digital signal?

Thanks

[breese]

There are 4 PWM connections on the Pi. Here is the pinout guide.
https://pinout.xyz/

On the GPIO Imputs, test using the Commands Rising Edge, and the Commands Falling Edge.

[sdhin001]

I have it wired up and it does not work as intended.

It is constantly going between Rising and Falling triggers so the player is stopping and starting 3-4 times per second.

The exact same wiring setup, but with a Digital Output instead of a PWM signal works as intended. I have the capabilities of going between Digital and PWM with my radio transmitter so I know the wiring is ok.

Any other ideas?

[breese]

Sorry, Try using Rising only....
If that does not work, try Falling only.
Using both at the same time would cause the start and stop over and over again.

[tbone321]

I don't believe that a PWM signal is compatible with the current configuration of FPP.  I can't speak for Ver 8 since I haven't installed it on anything yet and probably will not until next year but unless they made some significant changes, I doubt that it will work there either.  

[breese]

There are a number of open and closed issues for PWM in the github.
Maybe one of the closed ones is the fix you are looking for.
https://github.com/FalconChristmas/fpp/issues?q=pwm

[tbone321]

There are a number of open and closed issues for PWM in the github.

The problem that I see is that these issues are for outputs but he is trying to use inputs.

[breese]

Looks like he needs to join the Xlights Zoom room...

[tbone321]

I agree

[MikeKrebs]

I think he needs to look at an external solution like a arduino, pico or stm. It is probably not going to be pretty doing pwm decoding on the RPi while running FPP. The RC PWM seems pretty slow (50Hz?) and the pulse width is apparently only two values but to read it reliably and decode it is probably going to stress FPP. 

If someone can figure it out, it would be pretty cool as another way to get input.

[tbone321]

It's not just 2 values, but the time interval between them and like you said, that could be rather taxing on FPP, especially if you are monitoring multiple pins and then determining what interval to trigger on and if you are looking for specific intervals or changes in those intervals.  There are other ways to trigger events remotely like the big buttons plugin and a cell phone.

[sdhin001]

Thank you all for the replies.

So far, I have been able to use an external PWM to DC converter/interpreter. No issues there. The hope was that I would be able to do it on the Pi without an external component.

As it currently stands, I don't think FPP is able to do it. Super rare use case.