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git://projects.qi-hardware.com/antorcha.git
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72 lines
1.4 KiB
C
Executable File
72 lines
1.4 KiB
C
Executable File
#include <stdbool.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <math.h>
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#define G 28 /* 1 Earth gravity in accelerometer units */
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#define MID 512 /* accelerometer middle value */
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#define S 1000 /* sample rate (samples/s) */
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#define F 2 /* rotational speed in Hz */
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#define R 0.46 /* radius of accelerometer orbit */
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#define H (G/2) /* hysteresis, in accelerometer units */
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/* noise pattern: frequency, amplitude pairs */
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static struct noise {
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int f; /* frequency (in samples) */
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int a; /* amplitude (in accelerometer units) */
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} noise[] = {
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{ 1, G/3 }, /* general noise */
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{ S/F/10, 5*G }, /* hits caused by the chain "jumping" */
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{ 0, }
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};
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static uint16_t sample(double t)
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{
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int fz = R*4*M_PI*M_PI*F*F/9.81*G;
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int fg = cos(2*M_PI*F*t)*G;
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int f = fz+fg;
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const struct noise *n;
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for (n = noise; n->f; n++)
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if (!(random() % n->f))
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f += random() % (2*n->a) - n->a;
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return f+MID;
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}
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#define E_SHIFT 3 /* ~ 0.1 */
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#define M_SHIFT 10 /* ~ 1/S */
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int main(void)
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{
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uint16_t e = MID << E_SHIFT;
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uint32_t m = MID << M_SHIFT;
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int d;
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int i;
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bool up = 0;
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for (i = 0; i != 10*S; i++) {
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unsigned v = sample((double) i/S);
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e = v+(e-(e >> E_SHIFT));
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m = v+(m-(m >> M_SHIFT));
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d = (e >> E_SHIFT)-(m >> M_SHIFT);
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if (up) {
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if (d < -H)
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up = 0;
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} else {
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if (d > H)
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up = 1;
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}
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printf("%d %d %d %d %d\n",
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v, e >> E_SHIFT, m >> M_SHIFT, d, up);
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}
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return 0;
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}
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