Re: [Xenomai-help] rt usb

[Jan Kiszka <jan.kiszka@domain.hid>]

Roland Tollenaar wrote:
> Hi Jan,
> 
>>> Is any documentation available which clarifies why usb is a problem 
>>> and how big the problem is (perhaps I can risk it?:) )
>>
>> No longer at hand (a former student of mine did his diploma thesis 
>> about usb4rt). 
> Pity.
> 
>> Generally, there is no real show-stopper, we "just" need a 
>> real-time-aware stack that provides appropriate API (e.g. to 
> 
> So, if I run CAN over USB from a rt thread there is a chance that even 
> though it is not rt-safe, it may not screw up latency?
> 
> I realize that this will seem pointless and is technically incorrect but 
>  if for example the USB device is not addressed by any other processes, 
> what is the chance that I will have problems?

The things is just as with RTnet vs. standard Linux networking: You need 
a stack like the mentioned ones to provide rt-safe access to the USB 
hardware. For CAN (e.g. the Peak dongle), you then need a high-level USB 
driver that connects the RT-USB and RT-CAN stacks. But there is no point 
in trying to tunnel your USB requests through the Linux USB stack, I 
case you meant this.

Jan

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