- From: Tim Holt <holtt_at_nacse.org>
- Date: Fri, 23 Jan 2004 11:16:57 -0800
I've tried to do something similar with no luck on an NI PCI 6071E using
latest CVS from a few weeks ago.
Marc Rawji wrote:
> Hi,
>
> I am fairly new at data acquisition and Linux.
> I am using comedilib 0.7.20 and comedi 0.7.66.
>
> I am able to read and write to both analog and digital channels and I
> can perform continuous acquisition using comedi_command.
>
> Ok, here is the question:
>
> I want to use an external trigger to start an acquisition. This is
> what I have, and it doesn't work
>
> {
> ...
> // I set all the DIO channels (subdevices 2 and 7) as input.
>
> // create the command structure
> memset(&cmd, 0,sizeof(cmd));
> cmd.subdev = 0;
> cmd.flags = 0;
> cmd.start_src = TRIG_EXT;
> cmd.start_arg = 0;
> cmd.scan_begin_src = TRIG_TIMER;
> cmd.scan_begin_arg = 1e9*sampling_period;
> cmd.convert_src = TRIG_TIMER;
> cmd.convert_arg = 5000;
> cmd.scan_end_src = TRIG_COUNT;
> cmd.scan_end_arg = nchan;
> cmd.stop_src = TRIG_COUNT;
> cmd.stop_arg = totalsamples;
> cmd.chanlist = chanlist;
> cmd.chanlist_len = nchan;
> // test the command
> int ret = comedi_command_test(Dev, &cmd);
> if (ret != 0)
> {
> printf("An error occured in the command\n");
> exit(-1);
> }
> //make sure we are still using the same number of samples
> totalsamples = cmd.stop_arg;
> lsampl_t *data = new lsampl_t[totalsamples];
> int samples_read = 0;
> int buff_size = 32;
> char *buff = new char[buff_size];
> if (comedi_command(Dev, &cmd)<0)
> {
> comedi_perror("Comedi command not sent");
> exit(-1);
> }
>
> ... read from /dev/comedi0 and do whatever...
> }
>
> as I understand it, as soon as there is a rising or falling edge to
> PFI0, the board should start the acquisition.
>
> As of now, no errors are returned by any comedi functions, nor by the
> read function. The read function just waits for data to become
> available. Everything works if I set the trigger to TRIG_INT and send
> a software trigger.
>
> Thanks,
> Marc
>
>
>
>
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Received on 2004-01-23Z19:16:57