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101 lines
2.1 KiB
C
101 lines
2.1 KiB
C
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/*
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* atrf-xtal/atusb.c - ATUSB-specific driver and evaluation
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*
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* Written 2011 by Werner Almesberger
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* Copyright 2011 Werner Almesberger
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <sys/time.h>
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#include <usb.h>
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#include <gsl/gsl_fit.h>
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#include "at86rf230.h"
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#include "atusb/ep0.h"
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#include "atrf.h"
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#include "atrf-xtal.h"
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#define FROM_DEV ATUSB_FROM_DEV(0)
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#define F_NOMINAL_Hz 8000000 /* nominal frequency, in Hz */
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static uint64_t get_sample(struct atrf_dsc *dsc, double *t0, double *t1)
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{
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struct timeval tod0, tod1;
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uint64_t cnt;
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int res;
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gettimeofday(&tod0, NULL);
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res = usb_control_msg(atrf_usb_handle(dsc),
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FROM_DEV, ATUSB_TIMER, 0, 0, (void *) &cnt, sizeof(cnt), 1000);
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gettimeofday(&tod1, NULL);
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if (res < 0) {
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fprintf(stderr, "ATUSB_TIMER: %s\n", usb_strerror());
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exit(1);
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}
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*t0 = tod0.tv_sec+tod0.tv_usec/1000000.0;
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*t1 = tod1.tv_sec+tod1.tv_usec/1000000.0;
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return cnt;
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}
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void do_atusb(struct atrf_dsc *dsc, int trim, int dump_raw, double ppm,
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int n)
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{
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double t0[n], t1[n], cnt[n], w[n];
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double c0, c1, cov00, cov01, cov11, chisq;
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double d;
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double tz = 0, cntz = 0;
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double rel;
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int i;
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atrf_reg_write(dsc, REG_XOSC_CTRL,
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(XTAL_MODE_INT << XTAL_MODE_SHIFT) | trim);
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for (i = 0; i != n; i++) {
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cnt[i] = get_sample(dsc, t0+i, t1+i);
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if (!i) {
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tz = t0[0];
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cntz = cnt[0];
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}
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t0[i] -= tz;
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t1[i] -= tz;
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cnt[i] -= cntz;
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/*
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* see http://en.wikipedia.org/wiki/
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* Uniform_distribution_(continuous)
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*/
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d = (t1[i]-t0[i])*F_NOMINAL_Hz;
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w[i] = 12/(d*d);
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}
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if (dump_raw) {
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for (i = 0; i != n; i++)
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printf("%.6f %.6f %.0f\n", t0[i], t1[i], cnt[i]);
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return;
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}
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gsl_fit_wlinear (t0, 1, w, 1, cnt, 1, n,
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&c0, &c1, &cov00, &cov01, &cov11, &chisq);
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rel = (c1/F_NOMINAL_Hz-1)*1000000;
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printf("%+.2f ppm", rel);
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if (ppm && fabs(rel) > ppm) {
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printf(" (outside bounds)\n");
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exit(1);
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}
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putchar('\n');
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}
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