mirror of https://github.com/ArduPilot/ardupilot
134 lines
3.2 KiB
C
134 lines
3.2 KiB
C
/*
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ADS7844 register emulation
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Code by Andrew Tridgell November 2011
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*/
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#ifndef _SITL_ADC_H
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#define _SITL_ADC_H
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#include <stdlib.h>
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#include <math.h>
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static const float vibration_level = 0.2;
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static const float drift_speed = 0.2; // degrees/second/minute
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static const float drift_time = 5; // time to reverse drift direction (minutes)
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// order zgyro, xgyro, ygyro, temp, xacc, yacc, zacc, aspd
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static const float noise_scale[8] = { 150, 150, 150, 0, 400, 400, 400, 0 };
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static const float noise_offset[8]= { 0, 0, 0, 0, 0, 0, 0, 0 };
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static const float drift_rate[8] = { 1.0, 1.0, 1.0, 0, 0, 0, 0, 0 };
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static const float base_noise = 2;
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// generate a random float between -1 and 1
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static double rand_float(void)
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{
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float ret = ((unsigned)random()) % 2000000;
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return (ret - 1.0e6) / 1.0e6;
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}
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static inline float gyro_drift(uint8_t chan)
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{
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if (drift_rate[chan] * drift_speed == 0.0) {
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return 0;
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}
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extern long unsigned int micros(void);
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double period = drift_rate[chan] * drift_time * 2;
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double minutes = fmod(micros() / 60.0e6, period);
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if (minutes < period/2) {
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return minutes * drift_speed / 0.4;
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}
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return (period - minutes) * drift_speed / 0.4;
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}
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static inline float noise_generator(uint8_t chan)
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{
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extern float sitl_motor_speed[4];
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uint8_t i;
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float noise = 0;
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uint8_t noise_count=0;
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extern long unsigned int micros(void);
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for (i=0; i<4; i++) {
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if (sitl_motor_speed[i] > 0.0) {
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float n = rand_float() * noise_scale[chan] * vibration_level;
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//double t = micros() / 1.0e6;
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//float freq = (rand_float() + 1.0) * sitl_motor_speed[i];
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//noise += sin(fmod(t * freq * 2 * M_PI + i,
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//2*M_PI)) * n;
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noise += n + noise_offset[chan];
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noise_count++;
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}
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}
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if (noise_count == 0) {
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return gyro_drift(chan) + rand_float() * base_noise * vibration_level;
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}
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return gyro_drift(chan) + noise/noise_count;
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}
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// this implements the UDR2 register
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struct ADC_UDR2 {
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uint16_t value, next_value;
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uint8_t idx;
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float channels[8];
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ADC_UDR2() {
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// constructor
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for (uint8_t i=0; i<8; i++) {
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channels[i] = 0xFFFF;
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}
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value = next_value = 0;
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idx = 0;
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}
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/*
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assignment of UDR2 selects which ADC channel
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to output next
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*/
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ADC_UDR2& operator=(uint8_t cmd) {
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float next_analog;
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uint8_t chan;
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switch (cmd) {
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case 0x87: chan = 0; break;
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case 0xC7: chan = 1; break;
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case 0x97: chan = 2; break;
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case 0xD7: chan = 3; break;
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case 0xA7: chan = 4; break;
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case 0xE7: chan = 5; break;
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case 0xB7: chan = 6; break;
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case 0xF7: chan = 7; break;
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case 0:
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default: return *this;
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}
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next_analog = channels[chan];
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idx = 1;
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next_analog += noise_generator(chan) + 0.5;
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if (next_analog > 0xFFF) next_analog = 0xFFF;
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if (next_analog < 0) next_analog = 0;
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next_value = ((unsigned)next_analog) << 3;
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return *this;
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}
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/*
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read from UDR2 fetches a byte from the channel
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*/
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operator int() {
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uint8_t ret;
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if (idx & 1) {
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ret = (value&0xFF);
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value = next_value;
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} else {
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ret = (value>>8);
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}
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idx ^= 1;
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return ret;
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}
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/*
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interface to set a channel value from SITL
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*/
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void set(uint8_t i, float v) {
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channels[i] = v;
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}
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};
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#endif // _SITL_ADC_H
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