ardupilot/libraries/AP_Airspeed/AP_Airspeed_I2C.cpp

117 lines
2.9 KiB
C++

/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
backend driver for airspeed from a I2C MS4525D0 sensor
*/
#include <AP_Common.h>
#include <AP_HAL.h>
#include <AP_Math.h>
#include <AP_Airspeed_I2C.h>
extern const AP_HAL::HAL& hal;
#define I2C_ADDRESS_MS4525DO 0x28
// probe and initialise the sensor
bool AP_Airspeed_I2C::init(void)
{
_measure();
hal.scheduler->delay(10);
_collect();
if (_last_sample_time_ms != 0) {
hal.scheduler->register_timer_process(AP_HAL_MEMBERPROC(&AP_Airspeed_I2C::_timer));
return true;
}
return false;
}
// start a measurement
void AP_Airspeed_I2C::_measure(void)
{
_measurement_started_ms = 0;
if (hal.i2c->writeRegisters(I2C_ADDRESS_MS4525DO, 0, 0, NULL) != 0) {
return;
}
_measurement_started_ms = hal.scheduler->millis();
}
// read the values from the sensor
void AP_Airspeed_I2C::_collect(void)
{
uint8_t data[4];
_measurement_started_ms = 0;
if (hal.i2c->read(I2C_ADDRESS_MS4525DO, 4, data) != 0) {
return;
}
uint8_t status = data[0] & 0xC0;
if (status == 2) {
return;
} else if (status == 3) {
return;
}
int16_t dp_raw, dT_raw;
dp_raw = (data[0] << 8) + data[1];
dp_raw = 0x3FFF & dp_raw;
dT_raw = (data[2] << 8) + data[3];
dT_raw = (0xFFE0 & dT_raw) >> 5;
_temperature = ((200 * dT_raw) / 2047) - 50;
_pressure = fabs(dp_raw - (16384 / 2.0f));
_last_sample_time_ms = hal.scheduler->millis();
}
// 1kHz timer
void AP_Airspeed_I2C::_timer(void)
{
if (_measurement_started_ms == 0) {
_measure();
return;
}
if ((hal.scheduler->millis() - _measurement_started_ms) > 10) {
_collect();
// start a new measurement
_measure();
}
}
// return the current differential_pressure in Pascal
bool AP_Airspeed_I2C::get_differential_pressure(float &pressure)
{
if ((hal.scheduler->millis() - _last_sample_time_ms) > 100) {
return false;
}
pressure = _pressure;
return true;
}
// return the current temperature in degrees C, if available
bool AP_Airspeed_I2C::get_temperature(float &temperature)
{
if ((hal.scheduler->millis() - _last_sample_time_ms) > 100) {
return false;
}
temperature = _temperature;
return true;
}