PPM with more than 8 channels

[Andrew Tridgell]

Hi Stefan,

I saw your request for more than 8 channel support for PPM. The key is
to get a developer with the ability to tackle this a PPM receiver that
can do more than 8 channels. What affordable systems are around that
could be bought for testing this?

Cheers, Tridge

[Josh Welsh]

Hey Tridge,

I personally use the EzUHF system. If you have a Taranis or JR, a module
can be purchased for $99 US and then a receiver for roughly that much more
again. Their 4-channel "lite" receiver can't be used as it doesn't
currently output more than 8ch.

I'd be very happy to help anyone through the testing process one on one if
you/they wanted to go that route. Don't know that me testing the code for
the remote developer is ideal, but via skype, etc., I'm sure we could make
it work if it comes to that. Like Stefan, I also have an interest in PPM
support above 8ch so I'd be willing to do whatever I could (outside sending
my gear) to help!

Josh

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[Brandon Clifford]

The Open LRS modules are super cheap and can do more then 8ch. Let me know if there is anything I could do to test as well. More then 8ch would be great! You can get those Orange LRS systems RX / TX for 50$ can't beat that.

[john...@gmail.com]

>8ch channels just means there are more channel pulses before the >4ms termination pulse. So support in the decoding part is trivial. The downside is that the channel refresh rate will be decreased since 8ch is the max you can have at ~50hz (8*2ms + 4ms). So 16ch will give you worst case 27hz channel refresh instead. It is of course possible to increase the refresh by using shorter pulse times then the standard 2ms, but then it's not standard PPM any longer and you run into a whole new range of problems trying to robustly detect what type of PPM signal is being received.

- JAB

[Josh Welsh]

Agreed, and suggest a configurable setting where the user can choose between 10, 12, 14, and 16 channels total so as not to sacrifice timing for 16 channels when the user may need only 10 decoded? Not sure how much that would complicate the refresh frequency?

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[john...@gmail.com]

As long as the decoder is able to decode >8ch and uses the termination pulse to count the number of channels received, this will be controlled by the radio receiver.
If the receiver transmitts 8 channels + termination then you get 8 channel timing, or if the receiver transmits 12ch + termination then you get that timing etc.

- JAB