/usr/share/doc/libcomedi-dev/demo/insn.c is in libcomedi-dev 0.10.2-2.
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* Instruction example
* Part of Comedilib
*
* Copyright (c) 1999,2000 David A. Schleef <ds@schleef.org>
*
* This file may be freely modified, distributed, and combined with
* other software, as long as proper attribution is given in the
* source code.
*/
/*
This example shows how to use instructions, i.e., comedi_insns.
Using instructions directly, as in this example, is not recommended
for the beginner. Use the higher-level functions such as
comedi_data_read(), comedi_data_write(), etc., as demonstrated
in the inp, outp, and dio examples. Then, if you need the
additional flexibility that using instructions directly
provides, study this example and the implementations of
comedi_data_read(), etc.
*/
#include <stdio.h>
#include <comedilib.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/time.h>
#include <unistd.h>
#include "examples.h"
/*
* This example does 3 instructions in one system call. It does
* a gettimeofday() call, then reads N_SAMPLES samples from an
* analog input, and the another gettimeofday() call.
*
* (Note: The gettimeofday() value is obtained using an INSN_GTOD
* instruction, which places the seconds value in data[0] and the
* microseconds in data[1], so the seconds value is limited to
* 32-bits even on 64-bit systems.)
*/
#define MAX_SAMPLES 128
comedi_t *device;
int main(int argc, char *argv[])
{
int ret,i;
comedi_insn insn[3];
comedi_insnlist il;
lsampl_t t1[2], t2[2];
lsampl_t data[MAX_SAMPLES];
struct parsed_options options;
init_parsed_options(&options);
options.n_scan = 10; /* override default n_scan value to something more suitable */
parse_options(&options, argc, argv);
if(options.n_scan > MAX_SAMPLES ){
fprintf( stderr, "Requested too many samples, reducing to %i\n", MAX_SAMPLES );
options.n_scan = MAX_SAMPLES;
}
device = comedi_open(options.filename);
if(!device){
comedi_perror(options.filename);
exit(-1);
}
if(options.verbose){
printf("measuring device=%s subdevice=%d channel=%d range=%d analog reference=%d\n",
options.filename, options.subdevice, options.channel, options.range, options.aref);
}
/* Set up a the "instruction list", which is just a pointer
* to the array of instructions and the number of instructions.
*/
il.n_insns=3;
il.insns=insn;
/* Instruction 0: perform a gettimeofday() */
insn[0].insn=INSN_GTOD;
insn[0].n=2;
insn[0].data=t1;
/* Instruction 1: do 10 analog input reads */
insn[1].insn=INSN_READ;
insn[1].n = options.n_scan;
insn[1].data=data;
insn[1].subdev = options.subdevice;
insn[1].chanspec=CR_PACK(options.channel, options.range, options.aref);
/* Instruction 2: perform a gettimeofday() */
insn[2].insn=INSN_GTOD;
insn[2].n=2;
insn[2].data=t2;
ret=comedi_do_insnlist(device,&il);
if(ret<0){
comedi_perror(options.filename);
exit(-1);
}
printf("initial time: %d.%06d\n", t1[0], t1[1]);
for(i = 0; i < options.n_scan; i++){
printf("%d\n", data[i]);
}
printf("final time: %d.%06d\n", t2[0], t2[1]);
printf("difference (us): %ld\n",(long)(t2[0]-t1[0]) * 1000000 +
(t2[1] - t1[1]));
return 0;
}
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