ardupilot/libraries/SITL/SIM_MS5611.cpp

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#include "SIM_MS5611.h"
#include <SITL/SITL.h>
#include <stdio.h>
using namespace SITL;
// forward conversion, copied from driver:
void MS5611::convert_forward(int32_t D1, int32_t D2, float &P_Pa, float &Temp_C)
{
// _D1 and _D2 are stored as floats in driver
const float _D1 = D1;
const float _D2 = D2;
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float dT;
float TEMP;
float OFF;
float SENS;
dT = _D2-(((uint32_t)prom[5])<<8);
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TEMP = (dT * prom[6])/8388608;
OFF = prom[2] * 65536.0f + (prom[4] * dT) / 128;
SENS = prom[1] * 32768.0f + (prom[3] * dT) / 256;
TEMP += 2000;
if (TEMP < 2000) {
// second order temperature compensation when under 20 degrees C
float T2 = (dT*dT) / 0x80000000;
float Aux = sq(TEMP-2000.0);
float OFF2 = 2.5f*Aux;
float SENS2 = 1.25f*Aux;
if (TEMP < -1500) {
// extra compensation for temperatures below -15C
OFF2 += 7 * sq(TEMP+1500);
SENS2 += sq(TEMP+1500) * 11.0*0.5;
}
TEMP = TEMP - T2;
OFF = OFF - OFF2;
SENS = SENS - SENS2;
}
P_Pa = (_D1*SENS/2097152 - OFF)/32768;
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Temp_C = TEMP * 0.01f;
}
void MS5611::convert(float P_Pa, float Temp_C, uint32_t &D1, uint32_t &D2)
{
const uint8_t Q1 = Qx_coeff[0];
const uint8_t Q2 = Qx_coeff[1];
const uint8_t Q3 = Qx_coeff[2];
const uint8_t Q4 = Qx_coeff[3];
const uint8_t Q5 = Qx_coeff[4];
const uint8_t Q6 = Qx_coeff[5];
const float TEMP = Temp_C * 100;
// second order temperature compensation when under 20 degrees C
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if (TEMP < 2000) {
// Solve the quadratic equation for D2 when TEMP < 2000
D2 = 128 * (2 * int64_t(prom[5]) - sqrt(sq(int64_t(prom[6])) - 131072 * (TEMP - 2000)) + int64_t(prom[6]));
// Must compute the pressure compensation values using D2
const float dT = float(D2) - (int64_t(prom[5]) << Q5);
float TEMP_forward = 2000 + (dT * int64_t(prom[6])) / (1L << Q6);
float OFF = int64_t(prom[2]) * (1L << Q2) + (int64_t(prom[4]) * dT) / (1L << Q4);
float SENS = int64_t(prom[1]) * (1L << Q1) + (int64_t(prom[3]) * dT) / (1L << Q3);
const float Aux = sq(TEMP_forward - 2000);
float OFF2 = 2.5 * Aux;
float SENS2 = 1.25 * Aux;
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if (TEMP < -1500) {
// extra compensation for temperatures below -15C
OFF2 += 7 * sq(TEMP_forward + 1500);
SENS2 += sq(TEMP_forward + 1500) * 11.0 * 0.5;
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}
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OFF = OFF - OFF2;
SENS = SENS - SENS2;
D1 = ((P_Pa * float(1L << 15) + OFF) * float(1L << 21)) / SENS;
} else {
const float dT = (TEMP - 2000) * (1L << Q6) / int64_t(prom[6]);
const float OFF = int64_t(prom[2]) * (1L << Q2) + (int64_t(prom[4]) * dT) / (1L << Q4);
const float SENS = int64_t(prom[1]) * (1L << Q1) + (int64_t(prom[3]) * dT) / (1L << Q3);
D1 = ((P_Pa * float(1L << 15) + OFF) * float(1L << 21)) / SENS;
D2 = dT + (int64_t(prom[5]) << Q5);
}
}
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void MS5611::check_conversion_accuracy(float P_Pa, float Temp_C, uint32_t D1, uint32_t D2)
{
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float f_P_Pa;
float f_Temp_C;
convert_forward(D1, D2, f_P_Pa, f_Temp_C);
if (fabs(f_P_Pa - P_Pa) > 0.2) {
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AP_HAL::panic("Invalid pressure conversion");
}
if (fabs(f_Temp_C - Temp_C) > 0.02) {
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AP_HAL::panic("Invalid temperature conversion");
}
}
void MS5611::get_pressure_temperature_readings(float &P_Pa, float &Temp_C)
{
float sigma, delta, theta;
float sim_alt = AP::sitl()->state.altitude;
sim_alt += 2 * rand_float();
AP_Baro::SimpleAtmosphere(sim_alt * 0.001f, sigma, delta, theta);
P_Pa = SSL_AIR_PRESSURE * delta;
Temp_C = KELVIN_TO_C(SSL_AIR_TEMPERATURE * theta) + AP::sitl()->temp_board_offset;
// TO DO add in temperature adjustment by inheritting from AP_Baro_SITL_Generic?
// AP_Baro_SITL::temperature_adjustment(P_Pa, Temp_C);
// TO DO add in wind correction by inheritting from AP_Baro_SITL_Generic?
// P_Pa += AP_Baro_SITL::wind_pressure_correction(instance);
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}