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ardupilot/libraries/AP_Baro/AP_Baro_BMP085.cpp

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/// -*- 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/>.
*/
/*
* APM_BMP085.cpp - Arduino Library for BMP085 absolute pressure sensor
* Code by Jordi Mu<4D>oz and Jose Julio. DIYDrones.com
* Sensor is conected to I2C port
* Sensor End of Conversion (EOC) pin is PC7 (30)
*
* Variables:
* RawTemp : Raw temperature data
* RawPress : Raw pressure data
*
* Temp : Calculated temperature (in 0.1<EFBFBD>C units)
* Press : Calculated pressure (in Pa units)
*
* Methods:
* Init() : Initialization of I2C and read sensor calibration data
* Read() : Read sensor data and calculate Temperature and Pressure
* This function is optimized so the main host don<6F>t need to wait
* You can call this function in your main loop
* It returns a 1 if there are new data.
*
* Internal functions:
* Command_ReadTemp(): Send commando to read temperature
* Command_ReadPress(): Send commando to read Pressure
* ReadTemp() : Read temp register
* ReadPress() : Read press register
*
*
*/
// AVR LibC Includes
#include <inttypes.h>
#include <AP_Common.h>
#include <AP_Math.h> // ArduPilot Mega Vector/Matrix math Library
#include <AP_HAL.h>
#include "AP_Baro_BMP085.h"
extern const AP_HAL::HAL& hal;
#define BMP085_ADDRESS 0x77 //(0xEE >> 1)
#define BMP085_EOC 30 // End of conversion pin PC7 on APM1
// the apm2 hardware needs to check the state of the
// chip using a direct IO port
// On APM2 prerelease hw, the data ready port is hooked up to PE7, which
// is not available to the arduino digitalRead function.
#if CONFIG_HAL_BOARD == HAL_BOARD_APM1
#define BMP_DATA_READY() hal.gpio->read(BMP085_EOC)
#else
// No EOC connection from Baro
// Use times instead.
// Temp conversion time is 4.5ms
// Pressure conversion time is 25.5ms (for OVERSAMPLING=3)
#define BMP_DATA_READY() (BMP085_State == 0 ? hal.scheduler->millis() > (_last_temp_read_command_time + 5) : hal.scheduler->millis() > (_last_press_read_command_time + 26))
#endif
// oversampling 3 gives 26ms conversion time. We then average
#define OVERSAMPLING 3
// Public Methods //////////////////////////////////////////////////////////////
bool AP_Baro_BMP085::init()
{
uint8_t buff[22];
hal.gpio->pinMode(BMP085_EOC, GPIO_INPUT);// End Of Conversion (PC7) input
// We read the calibration data registers
if (hal.i2c->readRegisters(BMP085_ADDRESS, 0xAA, 22, buff) != 0) {
healthy = false;
return false;
}
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;
//Send a command to read Temp
Command_ReadTemp();
BMP085_State = 0;
// init raw temo
RawTemp = 0;
healthy = true;
return true;
}
// Read the sensor. This is a state machine
// acumulate a new sensor reading
void AP_Baro_BMP085::accumulate(void)
{
if (!BMP_DATA_READY()) {
return;
}
if (BMP085_State == 0) {
ReadTemp();
} else {
ReadPress();
Calculate();
}
BMP085_State++;
if (BMP085_State == 5) {
BMP085_State = 0;
Command_ReadTemp();
} else {
Command_ReadPress();
}
}
// Read the sensor using accumulated data
uint8_t AP_Baro_BMP085::read()
{
if (_count == 0 && BMP_DATA_READY()) {
accumulate();
}
if (_count == 0) {
return 0;
}
_last_update = hal.scheduler->millis();
Temp = 0.1f * _temp_sum / _count;
Press = _press_sum / _count;
_pressure_samples = _count;
_count = 0;
_temp_sum = 0;
_press_sum = 0;
return 1;
}
float AP_Baro_BMP085::get_pressure() {
return Press;
}
float AP_Baro_BMP085::get_temperature() {
return Temp;
}
// Private functions: /////////////////////////////////////////////////////////
// Send command to Read Pressure
void AP_Baro_BMP085::Command_ReadPress()
{
// Mode 0x34+(OVERSAMPLING << 6) is osrs=3 when OVERSAMPLING=3 => 25.5ms conversion time
uint8_t res = hal.i2c->writeRegister(BMP085_ADDRESS, 0xF4,
0x34+(OVERSAMPLING << 6));
_last_press_read_command_time = hal.scheduler->millis();
if (res != 0) {
healthy = false;
}
}
// Read Raw Pressure values
void AP_Baro_BMP085::ReadPress()
{
uint8_t buf[3];
if (!healthy && hal.scheduler->millis() < _retry_time) {
return;
}
if (hal.i2c->readRegisters(BMP085_ADDRESS, 0xF6, 3, buf) != 0) {
_retry_time = hal.scheduler->millis() + 1000;
hal.i2c->setHighSpeed(false);
healthy = false;
return;
}
RawPress = (((uint32_t)buf[0] << 16)
| ((uint32_t)buf[1] << 8)
| ((uint32_t)buf[2])) >> (8 - OVERSAMPLING);
}
// Send Command to Read Temperature
void AP_Baro_BMP085::Command_ReadTemp()
{
if (hal.i2c->writeRegister(BMP085_ADDRESS, 0xF4, 0x2E) != 0) {
healthy = false;
}
_last_temp_read_command_time = hal.scheduler->millis();
}
// Read Raw Temperature values
void AP_Baro_BMP085::ReadTemp()
{
uint8_t buf[2];
int32_t _temp_sensor;
if (!healthy && hal.scheduler->millis() < _retry_time) {
return;
}
if (hal.i2c->readRegisters(BMP085_ADDRESS, 0xF6, 2, buf) != 0) {
_retry_time = hal.scheduler->millis() + 1000;
hal.i2c->setHighSpeed(false);
healthy = false;
return;
}
_temp_sensor = buf[0];
_temp_sensor = (_temp_sensor << 8) | buf[1];
RawTemp = _temp_filter.apply(_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)RawTemp - 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) RawPress - 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 *= 0.5;
_press_sum *= 0.5;
_count /= 2;
}
}
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