RX - Support 16 channel PPM receivers

[secretspy711]

Cleanflight does not recognize the PPM stream coming from my DTF UHF receiver, but in Baseflight it works perfectly. I have it set to 12 channel PPM but the same problem occurs when it's set to 8-channel also. This video sums it up: http://www.youtube.com/watch?v=Wnf1iHivLzk

I tried again using a FrSky ppm capable receiver, and it works perfectly. Why not with the DTF UHF?

[secretspy711]

solved, solution described at the youtube link above. closing this issue.

[ledvinap]

Could you post your solution here, please? Video is IMO terrible format to document it ...

On Mon, Jan 12, 2015 at 2:00 AM, secretspy711 notifications@github.com wrote:

solved, solution described at the youtube link above. closing this issue.

— Reply to this email directly or view it on GitHub https://github.com/cleanflight/cleanflight/issues/343#issuecomment-69520903 .

  Ing. Petr Ledvina
   ekoTIP ID s.r.o.

identifikační technologie Hálkova 1507/50 30100 Plzeň tel:608101056 www: ekotip.cz ledvina@ekotip.cz

[thenickdude]

It's in the video description:

Update 1/11/2015, SOLVED:

While fiddling with this today, I realized that even though I need more than 8 channels in total, I only need 8 within the PPM stream. So I went into the DTF UHF transmitter settings and realized that I had it set to 16 channels instead of 12 or 8 , and also the receiver option to "limit ppm output to 8 channels" set to "no." I must have done that a while back, thinking one day I might have a need for 16 channels.

Setting it to 12 channels instead of 16 solved the problem. Setting the option to "limit ppm output to 8 channels" set to "yes" also worked, when it was still set to 16-channel PPM.

[hydra]

The problem was that his tx was set to 16channel ppm when CH didn't work. Setting it to 12 fixed the problem.

I don't consider that a solution though so I will change this ticket to a feature request to support the 16ch ppm of that receiver.

I suspect that its likely a simple timing configuration in the ppm code that needs adjusting to deal with what I suspect is either a longer frame or a shorter delay between frames.

The ppm code in cleanflight is much more robust than the code in baseflight I would add.

[ledvinap]

#define MAX_SUPPORTED_RC_PPM_CHANNEL_COUNT 12

#define PPM_CAPTURE_COUNT 12
#define PWM_PORTS_OR_PPM_CAPTURE_COUNT PPM_CAPTURE_COUNT
#define PPM_IN_MAX_NUM_CHANNELS     PWM_PORTS_OR_PPM_CAPTURE_COUNT

[hydra]

Hahha yeah. Could be that :)

[hydra]

@secretspy711 please try this

https://www.dropbox.com/s/gy2a6frij1hbknv/cleanflight_NAZE-16CH-PPM.hex?dl=0

I created a new branch for this with the changes, you can see them here:

https://github.com/cleanflight/cleanflight/commits/ppm-16ch

baseflight only supports 8 channels so it was just reading the first 8 channels and ignoring the rest. Cleanflight first checks the ppm stream is valid before using it.

https://github.com/multiwii/baseflight/blob/master/src/drv_pwm.h#L9 https://github.com/multiwii/baseflight/blob/master/src/drv_pwm.c#L291-L312

vs

https://github.com/cleanflight/cleanflight/blob/master/src/main/drivers/pwm_rx.c#L142-L227

I did a video about the differences here:

https://www.youtube.com/watch?v=EViw4lBRa94

[secretspy711]

@hydra that binary works perfectly when my UHF system is set to 16 channels :) I can tell by watching the bars move that there's just a bit of latency (as expected), but it definitely works. Thank you.

[jamesboone]

@hydra is this fix now in the stable master branch?

[Lordnibbler]

@hydra any chance we can get this merged? i see its still not in master https://github.com/cleanflight/cleanflight/blob/master/src/main/drivers/pwm_rx.c#L38

[JohnieBraaf]

Would be nice if this was a cli option

[hydra]

I'll look into at merging the commits in that branch.

[007trains]

@hydra Any updates on this? Been quiet for over a year