ardupilot/libraries/AP_HAL_SITL/sitl_barometer.cpp

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/*
SITL handling
This simulates a barometer
Andrew Tridgell November 2011
*/
#include <AP_HAL/AP_HAL.h>
#include <AP_Math/AP_Math.h>
#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
#include "AP_HAL_SITL.h"
using namespace HALSITL;
extern const AP_HAL::HAL& hal;
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <math.h>
/*
setup the barometer with new input
altitude is in meters
*/
void SITL_State::_update_barometer(float altitude)
{
static uint32_t last_update;
float sim_alt = altitude;
if (_barometer == NULL) {
// this sketch doesn't use a barometer
return;
}
if (_sitl->baro_disable) {
// barometer is disabled
return;
}
// 80Hz, to match the real APM2 barometer
uint32_t now = hal.scheduler->millis();
if ((now - last_update) < 12) {
return;
}
last_update = now;
sim_alt += _sitl->baro_drift * now / 1000;
sim_alt += _sitl->baro_noise * _rand_float();
// add baro glitch
sim_alt += _sitl->baro_glitch;
// add delay
uint32_t best_time_delta_baro = 200; // initialise large time representing buffer entry closest to current time - delay.
uint8_t best_index_baro = 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_baro >= 10) { // store data every 10 ms.
last_store_time_baro = now;
if (store_index_baro > baro_buffer_length-1) { // reset buffer index if index greater than size of buffer
store_index_baro = 0;
}
buffer_baro[store_index_baro].data = sim_alt; // add data to current index
buffer_baro[store_index_baro].time = last_store_time_baro; // add time_stamp_baro to current index
store_index_baro = store_index_baro + 1; // increment index
}
// return delayed measurement
delayed_time_baro = now - _sitl->baro_delay; // get time corresponding to delay
// find data corresponding to delayed time in buffer
for (uint8_t i=0; i<=baro_buffer_length-1; i++) {
time_delta_baro = abs(delayed_time_baro - buffer_baro[i].time); // find difference between delayed time and time stamp in buffer
// if this difference is smaller than last delta, store this time
if (time_delta_baro < best_time_delta_baro) {
best_index_baro = i;
best_time_delta_baro = time_delta_baro;
}
}
if (best_time_delta_baro < 200) { // only output stored state if < 200 msec retrieval error
sim_alt = buffer_baro[best_index_baro].data;
}
_barometer->setHIL(sim_alt);
}
#endif