Re: [Paparazzi-devel] Suggestions

[Tilman Baumann]

On 12/12/13 10:53, Ben Laurie wrote:
> On 12 December 2013 08:59, Michal Podhradsky
> <address@hidden> wrote:
>> Hi Poine,
>>
>> we are working on RT Paparazzi (you can check out the current branch
>> (https://github.com/paparazzi/paparazzi/tree/rt_paparazzi) and we currently
>> have real time rotorcraft firmware. Partially because the code and control
>> loops was designed in quite a neat way.
> Curious: why is existing Paparazzi not RT?
It kind of is. It is designed similarly to the moon lander software. It
runs a list of functions at a fixed interval. The important ones first
the less important ones later.
If it can not finish execution of that list in time it will just start
over at the beginning of the list. This way the important functions can
not starve.

What the paparazzi_rt guys seemed to have done is to port the system to
a 'real' real-time operating system (ChibiOS).
To be honest, this was lacking in the paparazzi design for a long time.
The 'old' way of doing realtime was ok, bit with increasingly more
powerful CPU and the demand to run all sorts of other functions on the
same chip a proper realtime OS would help a lot.
I haven't looked into how much they achieved and how ambitious they do
it. You could just run ppz in one or two tasks (ap and fbw) and keep the
internal interval scheduler. Or you could split all internal ppz tasks
into Chibi tasks...


PS: Sorry this was a very high level view. Hope that it what you where
after.