Hello,

the FT2232 knows other operation modes than the pure RS232 one. CPU
host emulation for example allows to access simple bus connected devices.

The SJA1000 is a CAN Bus Controller.There are projects using the SJA1000 on
an ISA or PCI cards or connected to the parallel port. The task breaks down
to reading and writing to the controller and waiting for an interrupt
triggered by the controller. Canbus4linux
http://sourceforge.net/projects/canbus4linux is one driver framework, using
the parport framweork to access the paralle port connected device.

On page 45 of the FT2232 datasheet
http://www.ftdichip.com/Documents/DataSheets/ds2232c_15.pdf such a SJA1000
Controller is shown connected to the FT2232. I would like to extend the
canbus4linux driver for that setup. Implementing Read/Write access to the
controller via USB is straightforward, at least as long as performance
issues are left aside and things happen in small chunks. I know about the
round trip times needed for writing USB packages...

However for mapping the interrupt mechanism available in the parport
framework to the USB layer I have no idea. In basic, the status register of
the SJA1000 needs to be polled at a high rate.1000 Hz would probably do,
like the time frame for non Full spped USB devices use. When a certain
condition is met, the USB layer needs to react appropriate and needs to
inform higher levels.

Is there already something like a parport framework for the USB layer? I
know about libusb, but it is in user space and has therefore some drawbacks,
but also some advantages...

Thanks for any pointers and help!
-- 
Uwe Bonnes                [EMAIL PROTECTED]

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------



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