Re: How to use comedi for synchronous acquisition

From: Bernd Porr <bp1_at_cn.stir.ac.uk> · Date: Sun, 18 May 2003 16:19:58 +0100

Hi!

you have to issue only _one_ command with TRIG_NONE for the stop_src 
argument:

        comedi_cmd *cmd=new comedi_cmd;

        int r = comedi_get_cmd_generic_timed(dev,
                                             subdevice,
                                             cmd,
                                             (int)(1e9/1000));
        if(r<0){
                printf("comedi_get_cmd_generic_timed failed\n");
                exit(-1);
        }

        /* Modify parts of the command */
        cmd->chanlist           = chanlist;
        cmd->chanlist_len       = n_chan;

        cmd->scan_end_arg = n_chan;

        cmd->stop_src=TRIG_NONE;
        cmd->stop_arg=0;
:

After you've issued the command you can do read-commands until you 
cancel the aquisition.

/Bernd

Cheng-Ling Kuo wrote:

>Hi, 
>
>   I want to use  comedi for synchronous acquisition.
>   To do an acquisition at 8 khz freq, record data into a file on linux every day.
>   Could you tell me any example or suggestions?
>
>   I tried the function "comedi_command", but it seem asynchronous.
>   It losts data between two "comedi_command"s.
>
>   The document says that comedi_do_insn is synchronous. But how to do it?
>
>   Thanks a lot!
>
>Best regards, 
>
>Cheng-Ling Kuo
>
>Tel:+886-6-2757575-65276 
>Fax:+886-6-2096035 
> 
>Assistant Engineer 
>Science Data Distribution Center 
>ISUAL Project, The Scientific Payload of ROCSAT-2 
>Department of Physics 
>National Cheng Kung University 
>(http://www.phys.ncku.edu.tw) 
>
>_______________________________________________
>comedi mailing list
>comedi_at_comedi.org
>https://cvs.comedi.org/cgi-bin/mailman/listinfo/comedi
>  
>

-- 
http://www.cn.stir.ac.uk/~bp1/
mailto:bp1_at_cn.stir.ac.uk