Re: [Xenomai-help] DAQ SYSTEM COMPATIBILITY

[Anders Blomdell <anders.blomdell@domain.hid>]

Alexis Berlemont wrote:
> Hi,
> 
>> i need to buy an USB DAQ system and use it with Xenomai. I have an eye
>> on the National Instruments USB 6218 which is provided with linux drivers.
>> How can we now if an hardware will be usable with Xenomai ? 
>> Do we need 
>> the driver sources in order to be able to rewrite it for real time
>> purposes ?
> 
> A nice way would be to recover the Linux driver and make it work with Comedi 
> (which is a kind of framework for acquisition drivers, an RTDM port is 
> available).
> 
> Do you have the driver sources ? Just to see how it works...
> 
> To fully comply with real-time constraints, maybe usb20rt might be 
> necessary...
Another thing to keep in mind when using USB, is that USB microframes/frames are
only sent each 125 us/1 ms which gives a limit to how fast a control loop can
possibly be closed over USB (8kHz/1kHz, which is way below what can achieved
with USB if only data acquisition is needed).

Best regards

Anders Blomdell


-- 
Anders Blomdell                  Email: anders.blomdell@domain.hid
Department of Automatic Control
Lund University                  Phone:    +46 46 222 4625
P.O. Box 118                     Fax:      +46 46 138118
SE-221 00 Lund, Sweden