- From: Mike Reedy <mike_reedy_at_yahoo.com>
- Date: Mon, 19 Apr 2004 19:03:36 -0700 (PDT)
Hi all, Experimenting with comedilib/demo/mmap.c with Computer Boards pcidas64/16. Repeatedly executing "mmap" with "-nx", which sets the channel count to x, with a dead short on channel 0 Analog input, I see the shorted channel's data change position within the data scan. In other words, the short may appear as channel 0, I Control-C & rerun mmap & I may see the short in column 10, or any other column. Clearly there is some residual data somewhere offsetting the digital data by varying amounts. For anyone that has not tried mmap, it produces a tabular output to the CRT, one column per channel. I modified the output slightly, subtracting 32768 from the A/D count values which, combined with range 0 (+-10V) range, makes the shorted channel stand out. The short gives about 10 A/D counts while the remaining channels drift at several thousand counts. I have found a work around however. By executing "mmap -n1", the next execution of mmap works properly. Can anyone tell me how to clear all buffers & reset all pointers prior to starting a continuous analog acquisition command? Setup: Slackware 9.1, 2.4.25 kernel comedilib & comedi from CVS except cb_pcidas64 taken from comedi-0.7.67 since CVS version hung my system. I'd appreciate the help folks, Mike Reedy __________________________________ Do you Yahoo!? Yahoo! Photos: High-quality 4x6 digital prints for 25¢ http://photos.yahoo.com/ph/print_splash
Received on 2004-04-20Z01:03:36