- From: Calin A. Culianu <calin_at_ajvar.org>
- Date: Wed, 31 Aug 2005 18:59:45 -0400 (EDT)
I'm trying to see if it's possible to do very fast digital I/O from a real-time loop synchronously (I might want to do control from within the loop, which is why synch. I/O is the way to go for me). On my current hardware it seems a read/write to all 24 channels of my NI DaqCard DIO 24 takes 10 microseconds or so. That would mean I can't very well achieve rates above 100KHz. Any ideas if the 10us time for the comedi_insn is a limit of the PCI bus somehow or more likely a limit of the speed of the I/O card? BTW: A look at the 8255 driver seems to indicate writing to all 24 channels takes 6 outb instructions which presumably become 6 separate PCI Write operations -- each of which takes 4 PCI cycles minimum so that would mean 24 PCI cycles per DIO read/write... that should mean I could easily get over 1MHz transfer rates... but instead 1KHz is my limit... Any thoughts would be appreciated.. -Calin
Received on 2005-08-31Z21:59:45