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Re: [Paparazzi-devel] Increasing PPM rate


From: Christophe De Wagter
Subject: Re: [Paparazzi-devel] Increasing PPM rate
Date: Wed, 27 Jun 2012 11:20:50 +0200

Many digital receivers have a few fast channels and a few slow channels.  When using a ppm encoder that waits for all pulses to arrive you end up with only the slower. The value you see in paparazzi is what you get. Anything above 20 is good enough to fly. So no issue here. I'm not sure you can redefine the frame rate so the gcs is back green?

On Jun 27, 2012 4:55 AM, "Stephen Dwyer" <address@hidden> wrote:
Hello,

I am not 100% sure, but I think the ppm_rate is the frequency at which
ppm frames are received, based on the count of good ppm frames in 1
second. If that is the case, it would make sense if different
receivers had values less than 50(Hz) because some RC systems run with
a lower update rate. A good example is using Spektrum systems at 22ms
(~45Hz). I think some receivers have constant period and varying reset
times, while others have constant resets and varying periods. For the
ppm encoder, you can actually change these parameters, with the
default being the reset period is constant but the total PPM frame
period is varying, so it might change a bit.

So, I don't think you can really expect it to be 50 every time, and
having a different value is fine. Hope that clears things up a bit.
Someone please correct me if I am wrong.

Thanks,
-Stephen Dwyer

On Tue, Jun 26, 2012 at 7:44 PM, Chris Gough
<address@hidden> wrote:
> Hi Gareth,
>
> Me too, using "Cockpit SX -> IDP7 -> PPM encoder" (always has, right
> back to the SVN days). It did cause me pause to wonder, but  I'm not
> aware of it causing a problem.
>
> I never checked bcause I don't have a scope/logic analyser; is the PPM
> signal actually a bit slow (or is it being under reported)?
>
> Chris Gough
>
> On Wed, Jun 27, 2012 at 9:45 AM, Gareth Roberts
> <address@hidden> wrote:
>> Hi all,
>>
>> I've got a radio conf file that seems to be working fine, except that the
>> ppm_rate in messages is constantly around 47/48, rather than 50. It all
>> seems to work fine, and I've flown with it quite a few times without issue.
>>
>> The file in question is
>> https://github.com/blutack/paparazzi/blob/v3.9/conf/radios/FrSky_TFR4.xml
>>
>> I've searched both mailing list archives & code but can't figure out if this
>> is an issue, and if so how to solve it?
>> If anyone has any ideas, please let me know.
>>
>> Cheers,
>> Gareth
>>
>> _______________________________________________
>> Paparazzi-devel mailing list
>> address@hidden
>> https://lists.nongnu.org/mailman/listinfo/paparazzi-devel
>
>
>
> --
> .
>
> _______________________________________________
> Paparazzi-devel mailing list
> address@hidden
> https://lists.nongnu.org/mailman/listinfo/paparazzi-devel
>

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