Which DA card?

Hi,

I'm a German student working on a data acquisition project. For this project
we bought a PowerDAQ PD2-AO-8/16 AO card from UEIDAQ.com
(http://www.ueidaq.com/products/products.asp?MM_browse=true&pc_RecordId=59&pt_RecordId=7&pn_RecordId=5&MM_RecordId=202). The card shall output up to 8 analog signals which
are calculated in a realtime task using RTLinux. The card works fine except
that we are only able to use interrupt driven communication, i.e. at a specific
rate the card generates an interrupt and the realtime task is triggered to
calculate the signals and to send them to the card to be converted. Of course
this solution using interrupts is very slow and instable. We messured a
maximum interrupt rate of 50 usec delay. That's not enough, we need at least 25
usec. So we thought about using FIFO techniques using the driver shipped with
the card. The driver isn't Open Source. So one idea was to precalculate 360
values and sending them as a packet to the card so that the card does the
output by itself independently from the rt-task. That would be much faster and
reliable. But the whole thing doesn't work. Either the driver or the card is not
working correct. We don't know what's wrong and ueidaq hasn't got a solution
yet!
Now we are planning to buy another card which supports the given
specifications we need:
- up to eight analog output channels (with 16bit resolution) and at least
two digital I/O lines
- the minimum delay between two conversations is 25 usec, so 100kS per
channel may be enough
- after every convertion one of the digital output line has to trigger an
external device, in this case the best method would be that the card generates
this signal by itself not affecting the rt-task
- the rt-task should only calculate the data, not spending to much time
communicating with the card (we need the CPU power for calculation), so DMA
access or mmio or similar techniques are preferred

Can you help me and recommend a card for this purpose (which is supported by
the comedi project)?
I've already visited the national instruments web site looking for the
PCI-6731 card. But a note in comedi/drivers/ni_pcimio.c file says that the digital
I/O lines may not work and streaming isn't supported.
Btw: Is there a driver for the a.m. PowerDAQ PD2-AO-8/16 card avaible or
currently developed?
If you have further questions please email me.

Regards,
Philipp Hasse

Received on 2003-06-21Z15:16:22