Possible CPPM issue, MultiWii / FrSky

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wilco1967
Posts: 156
Joined: Thu Aug 18, 2011 6:04 pm
Location: Winterswijk, Netherlands

Possible CPPM issue, MultiWii / FrSky

Post by wilco1967 »

I found some post by Kilrah over at the 9X forums about a possible frame length issue with FrSky CPPM receivers.

http://9xforums.com/forum/viewtopic.php?f=52&t=1044

I tried to duplicate his findings, with the MultiWii, and indeed found problems.
However, as far as I can tell without proper test equipment, it could also be an MultiWii CPPM decoding issue.... In that case, it might also happen with other CPPM receivers (not just FrSky).

BTW... I never experienced any problems in flight, so it is probably not a very serious in real life, but would like to understand what is causing this, and if it can (or need to be) solved

Please have a look over at the 9x forums for the full story by Kilrah.

Greetings,
Wilco.

aidensere07
Posts: 12
Joined: Fri Mar 16, 2012 3:47 pm

Re: Possible CPPM issue, MultiWii / FrSky

Post by aidensere07 »

I am having the same problem with this, if I activate aux 1,2,3 and 4 at the same time as using the sticks multiwii hangs and spazzes out and motors stop, is there any way we can sort this?

PatrikE
Posts: 1957
Joined: Tue Apr 12, 2011 6:35 pm
Location: Sweden
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Re: Possible CPPM issue, MultiWii / FrSky

Post by PatrikE »

I think @Undkon had some trouble like this to.
On one of the models the PPM frameLength was 33 instead of 22.5.

wilco1967
Posts: 156
Joined: Thu Aug 18, 2011 6:04 pm
Location: Winterswijk, Netherlands

Re: Possible CPPM issue, MultiWii / FrSky

Post by wilco1967 »

I used what I hope is a workaround on the aux switches...

Before I used +100% / high / 2000 on the aux switches for active, and 0% / mid / 1500 for off. After reading about this issue, I now use mid / 1500for active, and low / 1000 for off.... This should avoid most problems (I hope)....

Alexinparis
Posts: 1630
Joined: Wed Jan 19, 2011 9:07 pm

Re: Possible CPPM issue, MultiWii / FrSky

Post by Alexinparis »

I understand the phenomena.
And I think there is nothing we can really do to avoid this...
when the overlapping condition is here, nothing can be done to detect the right sync matching the beginning of the PPM frame.

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