259 lines
7 KiB
C
259 lines
7 KiB
C
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/*
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* NI general-purpose counter example. Configures the counter to
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* produce a continuous pulse train. The argument specifies the
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* number of nanoseconds the output pulse should remain high.
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* The example assumes the board has already been configured to
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* route the output signal of the counter to an appropriate
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* location (you may need to route it to a PFI output line
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* for example).
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* Part of Comedilib
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*
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* Copyright (c) 2007 Frank Mori Hess <fmhess@users.sourceforge.net>
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*
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* This file may be freely modified, distributed, and combined with
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* other software, as long as proper attribution is given in the
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* source code.
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*/
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/*
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* Requirements: A board with a National Instruments general-purpose
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* counter, and comedi driver version 0.7.74 or newer.
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*/
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <comedilib.h>
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#include <math.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <getopt.h>
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#include <ctype.h>
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#include "examples.h"
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/*FIXME: move helper functions to common.c so they can be used on other (mostly counter) examples*/
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int arm(comedi_t *device, unsigned subdevice, lsampl_t source)
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{
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comedi_insn insn;
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lsampl_t data[2];
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int retval;
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memset(&insn, 0, sizeof(comedi_insn));
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insn.insn = INSN_CONFIG;
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insn.subdev = subdevice;
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insn.chanspec = 0;
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insn.data = data;
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insn.n = sizeof(data) / sizeof(data[0]);
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data[0] = INSN_CONFIG_ARM;
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data[1] = source;
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retval = comedi_do_insn(device, &insn);
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if(retval < 0)
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{
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fprintf(stderr, "%s: error:\n", __FUNCTION__);
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comedi_perror("comedi_do_insn");
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return retval;
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}
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return 0;
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}
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/* This resets the count to zero and disarms the counter. The counter output
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is set low. */
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int reset_counter(comedi_t *device, unsigned subdevice)
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{
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comedi_insn insn;
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lsampl_t data[1];
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int retval;
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memset(&insn, 0, sizeof(comedi_insn));
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insn.insn = INSN_CONFIG;
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insn.subdev = subdevice;
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insn.chanspec = 0;
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insn.data = data;
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insn.n = sizeof(data) / sizeof(data[0]);
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data[0] = INSN_CONFIG_RESET;
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retval = comedi_do_insn(device, &insn);
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if(retval < 0)
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{
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fprintf(stderr, "%s: error:\n", __FUNCTION__);
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comedi_perror("comedi_do_insn");
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return retval;
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}
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return 0;
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}
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int set_counter_mode(comedi_t *device, unsigned subdevice, lsampl_t mode_bits)
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{
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comedi_insn insn;
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lsampl_t data[2];
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int retval;
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memset(&insn, 0, sizeof(comedi_insn));
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insn.insn = INSN_CONFIG;
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insn.subdev = subdevice;
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insn.chanspec = 0;
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insn.data = data;
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insn.n = sizeof(data) / sizeof(data[0]);
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data[0] = INSN_CONFIG_SET_COUNTER_MODE;
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data[1] = mode_bits;
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retval = comedi_do_insn(device, &insn);
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if(retval < 0)
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{
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fprintf(stderr, "%s: error:\n", __FUNCTION__);
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comedi_perror("comedi_do_insn");
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return retval;
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}
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return 0;
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}
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int set_clock_source(comedi_t *device, unsigned subdevice, lsampl_t clock, lsampl_t period_ns)
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{
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comedi_insn insn;
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lsampl_t data[3];
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int retval;
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memset(&insn, 0, sizeof(comedi_insn));
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insn.insn = INSN_CONFIG;
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insn.subdev = subdevice;
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insn.chanspec = 0;
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insn.data = data;
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insn.n = sizeof(data) / sizeof(data[0]);
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data[0] = INSN_CONFIG_SET_CLOCK_SRC;
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data[1] = clock;
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data[2] = period_ns;
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retval = comedi_do_insn(device, &insn);
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if(retval < 0)
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{
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fprintf(stderr, "%s: error:\n", __FUNCTION__);
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comedi_perror("comedi_do_insn");
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return retval;
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}
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return 0;
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}
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int set_gate_source(comedi_t *device, unsigned subdevice, lsampl_t gate_index, lsampl_t gate_source)
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{
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comedi_insn insn;
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lsampl_t data[3];
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int retval;
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memset(&insn, 0, sizeof(comedi_insn));
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insn.insn = INSN_CONFIG;
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insn.subdev = subdevice;
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insn.chanspec = 0;
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insn.data = data;
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insn.n = sizeof(data) / sizeof(data[0]);
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data[0] = INSN_CONFIG_SET_GATE_SRC;
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data[1] = gate_index;
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data[2] = gate_source;
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retval = comedi_do_insn(device, &insn);
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if(retval < 0)
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{
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fprintf(stderr, "%s: error:\n", __FUNCTION__);
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comedi_perror("comedi_do_insn");
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return retval;
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}
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return 0;
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}
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int ni_gpct_start_pulse_generator(comedi_t *device, unsigned subdevice, unsigned period_ns, unsigned up_time_ns)
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{
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int retval;
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lsampl_t counter_mode;
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const unsigned clock_period_ns = 50; /* 20MHz clock */
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unsigned up_ticks, down_ticks;
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/*
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FIXME:
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How is output initialized to known state for toggling (reset?)
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*/
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retval = reset_counter(device, subdevice);
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if(retval < 0) return retval;
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retval = set_gate_source(device, subdevice, 0, NI_GPCT_DISABLED_GATE_SELECT | CR_EDGE);
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if(retval < 0) return retval;
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retval = set_gate_source(device, subdevice, 1, NI_GPCT_DISABLED_GATE_SELECT | CR_EDGE);
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if(retval < 0)
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{
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fprintf(stderr, "Failed to set second gate source. This is expected for older boards (e-series, etc.)\n"
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"that don't have a second gate.\n");
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}
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counter_mode = NI_GPCT_COUNTING_MODE_NORMAL_BITS;
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// toggle output on terminal count
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counter_mode |= NI_GPCT_OUTPUT_TC_TOGGLE_BITS;
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// load on terminal count
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counter_mode |= NI_GPCT_LOADING_ON_TC_BIT;
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// alternate the reload source between the load a and load b registers
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counter_mode |= NI_GPCT_RELOAD_SOURCE_SWITCHING_BITS;
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// count down
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counter_mode |= NI_GPCT_COUNTING_DIRECTION_DOWN_BITS;
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// initialize load source as load b register
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counter_mode |= NI_GPCT_LOAD_B_SELECT_BIT;
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retval = set_counter_mode(device, subdevice, counter_mode);
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if(retval < 0) return retval;
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/* 20MHz clock */
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retval = set_clock_source(device, subdevice, NI_GPCT_TIMEBASE_1_CLOCK_SRC_BITS, clock_period_ns);
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if(retval < 0) return retval;
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up_ticks = (up_time_ns + clock_period_ns / 2) / clock_period_ns;
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down_ticks = (period_ns + clock_period_ns / 2) / clock_period_ns - up_ticks;
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/* set initial counter value by writing to channel 0 */
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retval = comedi_data_write(device, subdevice, 0, 0, 0, down_ticks);
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if(retval < 0) return retval;
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/* set "load a" register to the number of clock ticks the counter output should remain low
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by writing to channel 1. */
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comedi_data_write(device, subdevice, 1, 0, 0, down_ticks);
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if(retval < 0) return retval;
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/* set "load b" register to the number of clock ticks the counter output should remain high
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by writing to channel 2 */
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comedi_data_write(device, subdevice, 2, 0, 0, up_ticks);
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if(retval < 0) return retval;
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retval = arm(device, subdevice, NI_GPCT_ARM_IMMEDIATE);
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if(retval < 0) return retval;
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return 0;
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}
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int main(int argc, char *argv[])
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{
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comedi_t *device;
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unsigned up_time;
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unsigned period_ns;
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int retval;
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struct parsed_options options;
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init_parsed_options(&options);
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options.value = -1.;
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parse_options(&options, argc, argv);
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period_ns = lrint(1e9 / options.freq);
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if(options.value < 0.)
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up_time = period_ns / 2;
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else
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up_time = lrint(options.value);
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device = comedi_open(options.filename);
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if(!device)
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{
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comedi_perror(options.filename);
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exit(-1);
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}
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/*FIXME: check that device is counter */
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printf("Generating pulse train on subdevice %d.\n", options.subdevice);
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printf("Period = %d ns.\n", period_ns);
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printf("Up Time = %d ns.\n", up_time);
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printf("Down Time = %d ns.\n", period_ns - up_time);
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retval = ni_gpct_start_pulse_generator(device, options.subdevice, period_ns, up_time);
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if(retval < 0) return retval;
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return 0;
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}
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