ardupilot/libraries/AP_Baro/AP_Baro_BMP085.cpp

242 lines
6.2 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/>.
*/
#include "AP_Baro_BMP085.h"
#include <utility>
#include <AP_Common/AP_Common.h>
#include <AP_HAL/AP_HAL.h>
extern const AP_HAL::HAL &hal;
#ifndef BMP085_EOC
#define BMP085_EOC -1
#endif
// oversampling 3 gives 26ms conversion time. We then average
#define OVERSAMPLING 3
AP_Baro_BMP085::AP_Baro_BMP085(AP_Baro &baro, AP_HAL::OwnPtr<AP_HAL::I2CDevice> dev)
: AP_Baro_Backend(baro)
, _dev(std::move(dev))
{
uint8_t buff[22];
// get pointer to i2c bus semaphore
AP_HAL::Semaphore *sem = _dev->get_semaphore();
// take i2c bus sempahore
if (!sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
AP_HAL::panic("BMP085: unable to get semaphore");
}
// End Of Conversion (PC7) input
if (BMP085_EOC >= 0) {
hal.gpio->pinMode(BMP085_EOC, HAL_GPIO_INPUT);
}
// We read the calibration data registers
if (!_dev->read_registers(0xAA, buff, 22)) {
AP_HAL::panic("BMP085: bad calibration registers");
}
ac1 = ((int16_t)buff[0] << 8) | buff[1];
ac2 = ((int16_t)buff[2] << 8) | buff[3];
ac3 = ((int16_t)buff[4] << 8) | buff[5];
ac4 = ((int16_t)buff[6] << 8) | buff[7];
ac5 = ((int16_t)buff[8] << 8) | buff[9];
ac6 = ((int16_t)buff[10] << 8) | buff[11];
b1 = ((int16_t)buff[12] << 8) | buff[13];
b2 = ((int16_t)buff[14] << 8) | buff[15];
mb = ((int16_t)buff[16] << 8) | buff[17];
mc = ((int16_t)buff[18] << 8) | buff[19];
md = ((int16_t)buff[20] << 8) | buff[21];
_last_press_read_command_time = 0;
_last_temp_read_command_time = 0;
_instance = _frontend.register_sensor();
// Send a command to read temperature
_cmd_read_temp();
BMP085_State = 0;
sem->give();
}
/*
This is a state machine. Acumulate a new sensor reading.
*/
void AP_Baro_BMP085::accumulate(void)
{
AP_HAL::Semaphore *sem = _dev->get_semaphore();
if (!_data_ready()) {
return;
}
// take i2c bus sempahore
if (!sem->take(1)) {
return;
}
if (BMP085_State == 0) {
_read_temp();
} else if (_read_pressure()) {
_calculate();
}
BMP085_State++;
if (BMP085_State == 5) {
BMP085_State = 0;
_cmd_read_temp();
} else {
_cmd_read_pressure();
}
sem->give();
}
/*
transfer data to the frontend
*/
void AP_Baro_BMP085::update(void)
{
if (_count == 0 && _data_ready()) {
accumulate();
}
if (_count == 0) {
return;
}
float temperature = 0.1f * _temp_sum / _count;
float pressure = _press_sum / _count;
_count = 0;
_temp_sum = 0;
_press_sum = 0;
_copy_to_frontend(_instance, pressure, temperature);
}
// Send command to Read Pressure
void AP_Baro_BMP085::_cmd_read_pressure()
{
// Mode 0x34+(OVERSAMPLING << 6) is osrs=3 when OVERSAMPLING=3 => 25.5ms conversion time
_dev->write_register(0xF4, 0x34 + (OVERSAMPLING << 6));
_last_press_read_command_time = AP_HAL::millis();
}
// Read raw pressure values
bool AP_Baro_BMP085::_read_pressure()
{
uint8_t buf[3];
if (!_dev->read_registers(0xF6, buf, 3)) {
_retry_time = AP_HAL::millis() + 1000;
_dev->set_speed(AP_HAL::Device::SPEED_LOW);
return false;
}
_raw_pressure = (((uint32_t)buf[0] << 16)
| ((uint32_t)buf[1] << 8)
| ((uint32_t)buf[2])) >> (8 - OVERSAMPLING);
return true;
}
// Send Command to Read Temperature
void AP_Baro_BMP085::_cmd_read_temp()
{
_dev->write_register(0xF4, 0x2E);
_last_temp_read_command_time = AP_HAL::millis();
}
// Read raw temperature values
void AP_Baro_BMP085::_read_temp()
{
uint8_t buf[2];
int32_t _temp_sensor;
if (!_dev->read_registers(0xF6, buf, 2)) {
_dev->set_speed(AP_HAL::Device::SPEED_LOW);
return;
}
_temp_sensor = buf[0];
_temp_sensor = (_temp_sensor << 8) | buf[1];
_raw_temp = _temp_sensor;
}
// _calculate Temperature and Pressure in real units.
void AP_Baro_BMP085::_calculate()
{
int32_t x1, x2, x3, b3, b5, b6, p;
uint32_t b4, b7;
int32_t tmp;
// See Datasheet page 13 for this formulas
// Based also on Jee Labs BMP085 example code. Thanks for share.
// Temperature calculations
x1 = ((int32_t)_raw_temp - ac6) * ac5 >> 15;
x2 = ((int32_t) mc << 11) / (x1 + md);
b5 = x1 + x2;
_temp_sum += (b5 + 8) >> 4;
// Pressure calculations
b6 = b5 - 4000;
x1 = (b2 * (b6 * b6 >> 12)) >> 11;
x2 = ac2 * b6 >> 11;
x3 = x1 + x2;
//b3 = (((int32_t) ac1 * 4 + x3)<<OVERSAMPLING + 2) >> 2; // BAD
//b3 = ((int32_t) ac1 * 4 + x3 + 2) >> 2; //OK for OVERSAMPLING=0
tmp = ac1;
tmp = (tmp*4 + x3)<<OVERSAMPLING;
b3 = (tmp+2)/4;
x1 = ac3 * b6 >> 13;
x2 = (b1 * (b6 * b6 >> 12)) >> 16;
x3 = ((x1 + x2) + 2) >> 2;
b4 = (ac4 * (uint32_t) (x3 + 32768)) >> 15;
b7 = ((uint32_t) _raw_pressure - b3) * (50000 >> OVERSAMPLING);
p = b7 < 0x80000000 ? (b7 * 2) / b4 : (b7 / b4) * 2;
x1 = (p >> 8) * (p >> 8);
x1 = (x1 * 3038) >> 16;
x2 = (-7357 * p) >> 16;
_press_sum += p + ((x1 + x2 + 3791) >> 4);
_count++;
if (_count == 254) {
_temp_sum *= 0.5f;
_press_sum *= 0.5f;
_count /= 2;
}
}
bool AP_Baro_BMP085::_data_ready()
{
if (BMP085_EOC >= 0) {
return hal.gpio->read(BMP085_EOC);
}
// No EOC pin: use time from last read instead.
if (BMP085_State == 0) {
return AP_HAL::millis() > _last_temp_read_command_time + 5;
}
return AP_HAL::millis() > _last_press_read_command_time + 26;
}