ardupilot/libraries/AP_Baro/AP_Baro_SITL.cpp

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#include <AP_HAL/AP_HAL.h>
#include <AP_Vehicle/AP_Vehicle_Type.h>
#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
#include "AP_Baro_SITL.h"
extern const AP_HAL::HAL& hal;
/*
constructor - registers instance at top Baro driver
*/
AP_Baro_SITL::AP_Baro_SITL(AP_Baro &baro) :
_sitl(AP::sitl()),
_has_sample(false),
AP_Baro_Backend(baro)
{
if (_sitl != nullptr) {
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_instance = _frontend.register_sensor();
#if APM_BUILD_TYPE(APM_BUILD_ArduSub)
_frontend.set_type(_instance, AP_Baro::BARO_TYPE_WATER);
#endif
hal.scheduler->register_timer_process(FUNCTOR_BIND(this, &AP_Baro_SITL::_timer, void));
}
}
// adjust for board temperature
void AP_Baro_SITL::temperature_adjustment(float &p, float &T)
{
const float tsec = AP_HAL::millis() * 0.001f;
const float T0 = _sitl->temp_start;
const float T1 = _sitl->temp_flight;
const float tconst = _sitl->temp_tconst;
const float baro_factor = _sitl->temp_baro_factor;
const float Tzero = 30.0f; // start baro adjustment at 30C
T = T1 - (T1 - T0) * expf(-tsec / tconst);
if (is_positive(baro_factor)) {
// this produces a pressure change with temperature that
// closely matches what has been observed with a ICM-20789
// barometer. A typical factor is 1.2.
p -= powf(MAX(T - Tzero, 0), baro_factor);
}
}
void AP_Baro_SITL::_timer()
{
// 100Hz
const uint32_t now = AP_HAL::millis();
if ((now - _last_sample_time) < 10) {
return;
}
_last_sample_time = now;
float sim_alt = _sitl->state.altitude;
if (_sitl->baro_disable) {
// barometer is disabled
return;
}
sim_alt += _sitl->baro_drift * now / 1000.0f;
sim_alt += _sitl->baro_noise * rand_float();
// add baro glitch
sim_alt += _sitl->baro_glitch;
// add delay
uint32_t best_time_delta = 200; // initialise large time representing buffer entry closest to current time - delay.
uint8_t best_index = 0; // initialise number representing the index of the entry in buffer closest to delay.
// storing data from sensor to buffer
if (now - _last_store_time >= 10) { // store data every 10 ms.
_last_store_time = now;
if (_store_index > _buffer_length - 1) { // reset buffer index if index greater than size of buffer
_store_index = 0;
}
_buffer[_store_index].data = sim_alt; // add data to current index
_buffer[_store_index].time = _last_store_time; // add time_stamp to current index
_store_index = _store_index + 1; // increment index
}
// return delayed measurement
const uint32_t delayed_time = now - _sitl->baro_delay; // get time corresponding to delay
// find data corresponding to delayed time in buffer
for (uint8_t i = 0; i <= _buffer_length - 1; i++) {
// find difference between delayed time and time stamp in buffer
uint32_t time_delta = abs(
(int32_t)(delayed_time - _buffer[i].time));
// if this difference is smaller than last delta, store this time
if (time_delta < best_time_delta) {
best_index = i;
best_time_delta = time_delta;
}
}
if (best_time_delta < 200) { // only output stored state if < 200 msec retrieval error
sim_alt = _buffer[best_index].data;
}
#if !APM_BUILD_TYPE(APM_BUILD_ArduSub)
float sigma, delta, theta;
AP_Baro::SimpleAtmosphere(sim_alt * 0.001f, sigma, delta, theta);
float p = SSL_AIR_PRESSURE * delta;
float T = 303.16f * theta - C_TO_KELVIN; // Assume 30 degrees at sea level - converted to degrees Kelvin
temperature_adjustment(p, T);
#else
float rho, delta, theta;
AP_Baro::SimpleUnderWaterAtmosphere(-sim_alt * 0.001f, rho, delta, theta);
float p = SSL_AIR_PRESSURE * delta;
float T = 303.16f * theta - C_TO_KELVIN; // Assume 30 degrees at sea level - converted to degrees Kelvin
#endif
_recent_press = p;
_recent_temp = T;
_has_sample = true;
}
// Read the sensor
void AP_Baro_SITL::update(void)
{
if (!_has_sample) {
return;
}
WITH_SEMAPHORE(_sem);
_copy_to_frontend(_instance, _recent_press, _recent_temp);
_has_sample = false;
}
#endif // CONFIG_HAL_BOARD