- From: John Conner <conner_at_empiredi.com>
- Date: Tue, 04 Jun 2002 18:38:16 -0600
Well I think I know why the CIO-DAS16JR is failing while the PC104-DAS16jr/16 works. The das16.c driver suggests a buffer size that will fill in 1/3 of a second - given the values I'm using this works out to 336 scans. Seems a bit familiar. So the driver has to process a dma interrupt every third of a second. The one thing I don't have is a number for is how long 1it takes to process the dma interrupt. My guess is something longer than 62 microseconds. There is one REALLY BIG but mostly undocumented difference between the CIO-DAS16jr and the PC104-DAS16jr/16. The PC104 Board has a FIFO! It does not have any real access the way most FIFOs do it just sets in the data path. The FIFO is 512 samples deep. The PC104-DAS16jr/12 also has the FIFO. What happens is that the boards continue generating samples while the DMA system is being reset and some of the samples are dropped on the CIO board. On the PC104 board they stack up in the FIFO and are eventually read out. Looks like current comedi das16 driver will not work at the rates I need with the CIO-DAS16jr boards. John Conner Empire Digital Instruments
Received on 2002-06-04Z23:38:16