ardupilot/libraries/Desktop/support/sitl_adc.h

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/*
ADS7844 register emulation
Code by Andrew Tridgell November 2011
*/
#ifndef _SITL_ADC_H
#define _SITL_ADC_H
#include <stdlib.h>
#include <math.h>
static const float vibration_level = 2.0;
static const float drift_level = 1.0;
// order zgyro, xgyro, ygyro, temp, xacc, yacc, zacc, aspd
static const float noise_scale[8] = { 150, 150, 150, 0, 400, 400, 400, 0 };
static const float noise_offset[8]= { 0, 0, 0, 0, 0, 0, 0, 0 };
static const float drift_rate[8] = { 0.7, 1.0, 0.5, 0, 0, 0, 0, 0 };
static const float base_noise = 2;
// generate a random float between -1 and 1
static double rand_float(void)
{
float ret = ((unsigned)random()) % 2000000;
return (ret - 1.0e6) / 1.0e6;
}
static inline float gyro_drift(uint8_t chan)
{
if (drift_rate[chan] * drift_level == 0.0) {
return 0;
}
extern long unsigned int micros(void);
double period = 10*drift_rate[chan] * drift_level;
double minutes = fmod(micros() / 60.0e6, period);
if (minutes < period/2) {
return minutes;
}
return period - minutes;
}
static inline float noise_generator(uint8_t chan)
{
extern float sitl_motor_speed[4];
uint8_t i;
float noise = 0;
uint8_t noise_count=0;
extern long unsigned int micros(void);
for (i=0; i<4; i++) {
if (sitl_motor_speed[i] > 0.0) {
float n = rand_float() * noise_scale[chan] * vibration_level;
//double t = micros() / 1.0e6;
//float freq = (rand_float() + 1.0) * sitl_motor_speed[i];
//noise += sin(fmod(t * freq * 2 * M_PI + i,
//2*M_PI)) * n;
noise += n + noise_offset[chan];
noise_count++;
}
}
if (noise_count == 0) {
return rand_float() * base_noise * vibration_level;
}
return gyro_drift(chan) + noise/noise_count;
}
// this implements the UDR2 register
struct ADC_UDR2 {
uint16_t value, next_value;
uint8_t idx;
float channels[8];
ADC_UDR2() {
// constructor
for (uint8_t i=0; i<8; i++) {
channels[i] = 0xFFFF;
}
value = next_value = 0;
idx = 0;
}
/*
assignment of UDR2 selects which ADC channel
to output next
*/
ADC_UDR2& operator=(uint8_t cmd) {
float next_analog;
uint8_t chan;
switch (cmd) {
case 0x87: chan = 0; break;
case 0xC7: chan = 1; break;
case 0x97: chan = 2; break;
case 0xD7: chan = 3; break;
case 0xA7: chan = 4; break;
case 0xE7: chan = 5; break;
case 0xB7: chan = 6; break;
case 0xF7: chan = 7; break;
case 0:
default: return *this;
}
next_analog = channels[chan];
idx = 1;
next_analog += noise_generator(chan) + 0.5;
if (next_analog > 0xFFF) next_analog = 0xFFF;
if (next_analog < 0) next_analog = 0;
next_value = ((unsigned)next_analog) << 3;
return *this;
}
/*
read from UDR2 fetches a byte from the channel
*/
operator int() {
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uint8_t ret;
if (idx & 1) {
ret = (value&0xFF);
value = next_value;
} else {
ret = (value>>8);
}
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idx ^= 1;
return ret;
}
/*
interface to set a channel value from SITL
*/
void set(uint8_t i, float v) {
channels[i] = v;
}
};
#endif // _SITL_ADC_H