- From: David Antliff <dave.antliff_at_paradise.net.nz>
- Date: Tue, 27 Aug 2002 15:30:23 +1200 (NZST)
Further to my previous email: Even though I don't have the top 8 channels working yet, something strange happens when I try to capture 16 channels at a sampling rate of 1kHz per channel (the card is supposed to work up to 20KHz which I'm assuming means 20/16 = 1.25kHz per channel over 16 channels). What happens is that the call to 'read' hangs/stops under certain circumstances. I've used some printfs and fflush() to verify this. GDB isn't a lot of help with this since it's happening inside libc. Here's some GDB output - first column is 'scan' (?) number (well, set of one sample from each of 16 channels), other columns are the channel data: (Note that channels 8 to 15 are zero, as per my previous email - I still haven't worked out what's going on there...) .... 474: 32690 32690 32690 32688 32690 32690 32688 32688 0 0 0 0 0 0 0 0 475: 32691 32690 32689 32688 32689 32690 32691 32690 0 0 0 0 0 0 0 0 476: 32692 32690 32688 32688 32688 32690 32690 32690 0 0 0 0 0 0 0 0 477: 32690 32689 32689 32688 32686 32688 32690 32689 0 0 0 0 0 0 0 0 478: 32690 32690 32690 32690 32689 32689 32690 32688 0 0 0 0 0 0 0 0 479: reading... Program received signal SIGINT, Interrupt. 0x400febb4 in read () from /lib/libc.so.6 (gdb) bt #0 0x400febb4 in read () from /lib/libc.so.6 #1 0x00000200 in ?? () #2 0x400550bf in __libc_start_main () from /lib/libc.so.6 The SIGINT is due to me hitting CTRL-C. It always happens during a 'read' and the exact read is seemingly random each time it is run. Just to recap - I'm trying to modify cmd.c to capture over 16 channels. I've tried sampling at the same rate over less channels. 8 always works. 9 works 99%ish of the time. 10 exhibits the problem more often and anything above this almost every run it stops. Reducing the sampling rate to 100Hz/channel also makes the problem go away for any number of channels. I've had a look through the entire comedi mailing list archive, but it's hard to find anything when I don't really know what I'm looking for - any help or a point in the right direction would be appreciated. Many thanks, David. David Antliff dave_at_med-dev.co.nz Design Engineer Med-Dev Ltd. tel. +64-4-972-7661 Wellington, New Zealand www.med-dev.co.nz
Received on 2002-08-27Z02:30:23