Re: [Xenomai-help] CAN errors and real-time behaviour

["Stéphane ANCELOT" <sancelot@domain.hid>]

Hi,
May be this related to your problem,I am trying to deal with some 
problems regarding CAN applications when NOTHING IS CONNECTED and my 
system  :

Like you I have a first  task that reads the CAN bus
a second task is doing nothing than waiting for a a semaphore.
A third  task begins to send two messages in can bus (the second message 
has got error) and goes to 5ms peridoic loop


The major problem is as follow :
I launch my RT TASK : no problem .I can do things in my linux console .

Now,  I start X , X begins to launch and is frozen.If I plug the bus 
CAN, "magician things " happen : X manage to launch and everything goes 
normal  ......

important NOTE for the behavour : CAN RX has got a timeout of almost 
100ms and tx of 10 ms. if something goes wrong task 2 rt_task_sleeps for 
a while.

I think the problem is related to can driver behavour.Do you think it is 
related to the same problem origin you have?


roland Tollenaar wrote:
> HI,
> 
> I thought I would put this in a separate thread.
> 
> The experiment works as follows. I have a 1ms and a 2 ms rt periodic task.
> 
> In the real-time periodic task I am only reading out the message
> buffer (only work done in the task). In the 2ms task I am doing
> nothing.
> 
> I always read-out the measured period times. This is done by writing
> the measured value into a variable which is displayed in a separate
> thread outside the rt tasks so the display does not influence the
> measurement. (Unlike  printf is said to do).
> 
> There is nothing connected to the rtcan2 device (Peak dongle). The
> applicaiton runs fine the tasktimes relatively well maintained
> (fluctuatin about 0.003ms) around 1ms and 2ms.
> 
> The moment I write to the device using rtcansend eg:
> ./rtcansend rtcan2 -i 0x700 0x03 0x02
> 
> the buserror comes up and the protocol error. from that moment onwards
> the messagebuffer gets flooded and does not stop being flooded forever
> after.
> 
> The period times then fluctuate badly up to 0.2ms around their nominal 
> values.
> 
> This is not desirable behavior. Firstly its not necessary to have the
> message buffer flooded all the time I would think. How do I change
> that so that I will only pick up an error once in response to a failed
> send?
> Secondly what am I doing wrong that breaks the real-time behaviour? If
> the bus gives an error on one part of the process I don;t want other
> processes that may have nothing to do with the CAN bus to misbehave.?
> 
> I do suspect that if I can prevent the message buffer flooding forever
> and manage to clean it out that the behaviour will be better because
> if its flooded then messages get sent to dmesg well wherever dmesg
> reads from that is) and this may explain the behavior?
> 
> Can anyone comment on this please?
> 
> Regards,
> 
> Roland.
> 
> _______________________________________________
> Xenomai-help mailing list
> Xenomai-help@domain.hid
> https://mail.gna.org/listinfo/xenomai-help
> 
>