/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- /* APM_BMP085.cpp - Arduino Library for BMP085 absolute pressure sensor Code by Jordi Mu�oz and Jose Julio. DIYDrones.com This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. 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�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�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 Calculate() : Calculate Temperature and Pressure in real units */ extern "C" { // AVR LibC Includes #include #include } #if defined(ARDUINO) && ARDUINO >= 100 #include "Arduino.h" #else #include "WConstants.h" #endif #include #include // ArduPilot Mega Vector/Matrix math Library #include #include "AP_Baro_BMP085.h" #define BMP085_ADDRESS 0x77 //(0xEE >> 1) #define BMP085_EOC 30 // End of conversion pin PC7 // 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. #define BMP_DATA_READY() (_apm2_hardware?(PINE&0x80):digitalRead(BMP085_EOC)) // oversampling 3 gives highest resolution #define OVERSAMPLING 3 // Public Methods ////////////////////////////////////////////////////////////// bool AP_Baro_BMP085::init( AP_PeriodicProcess * scheduler ) { byte buff[22]; pinMode(BMP085_EOC, INPUT); // End Of Conversion (PC7) input BMP085_State = 0; // Initial state // We read the calibration data registers if (I2c.read(BMP085_ADDRESS, 0xAA, 22, buff) != 0) { healthy = false; return false; } ac1 = ((int)buff[0] << 8) | buff[1]; ac2 = ((int)buff[2] << 8) | buff[3]; ac3 = ((int)buff[4] << 8) | buff[5]; ac4 = ((int)buff[6] << 8) | buff[7]; ac5 = ((int)buff[8] << 8) | buff[9]; ac6 = ((int)buff[10] << 8) | buff[11]; b1 = ((int)buff[12] << 8) | buff[13]; b2 = ((int)buff[14] << 8) | buff[15]; mb = ((int)buff[16] << 8) | buff[17]; mc = ((int)buff[18] << 8) | buff[19]; md = ((int)buff[20] << 8) | buff[21]; //Send a command to read Temp Command_ReadTemp(); BMP085_State = 1; // init raw temo RawTemp = 0; healthy = true; return true; } // Read the sensor. This is a state machine // We read Temperature (state=1) and then Pressure (state!=1) on alternate calls uint8_t AP_Baro_BMP085::read() { uint8_t result = 0; if (BMP085_State == 1){ if (BMP_DATA_READY()){ BMP085_State = 2; ReadTemp(); // On state 1 we read temp Command_ReadPress(); } }else{ if (BMP_DATA_READY()){ BMP085_State = 1; // Start again from state = 1 ReadPress(); Calculate(); Command_ReadTemp(); // Read Temp result = 1; // New pressure reading } } if (result) { _last_update = millis(); } return(result); } float AP_Baro_BMP085::get_pressure() { return Press; } float AP_Baro_BMP085::get_temperature() { return Temp; } int32_t AP_Baro_BMP085::get_raw_pressure() { return RawPress; } int32_t AP_Baro_BMP085::get_raw_temp() { return RawTemp; } // Private functions: ///////////////////////////////////////////////////////// // Send command to Read Pressure void AP_Baro_BMP085::Command_ReadPress() { if (I2c.write(BMP085_ADDRESS, 0xF4, 0x34+(OVERSAMPLING << 6)) != 0) { healthy = false; } } // Read Raw Pressure values void AP_Baro_BMP085::ReadPress() { uint8_t buf[3]; if (!healthy && millis() < _retry_time) { return; } if (I2c.read(BMP085_ADDRESS, 0xF6, 3, buf) != 0) { _retry_time = millis() + 1000; I2c.setSpeed(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 (I2c.write(BMP085_ADDRESS, 0xF4, 0x2E) != 0) { healthy = false; } } // Read Raw Temperature values void AP_Baro_BMP085::ReadTemp() { uint8_t buf[2]; int32_t _temp_sensor; if (!healthy && millis() < _retry_time) { return; } if (I2c.read(BMP085_ADDRESS, 0xF6, 2, buf) != 0) { _retry_time = millis() + 1000; I2c.setSpeed(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 = (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)<> 2; // BAD //b3 = ((int32_t) ac1 * 4 + x3 + 2) >> 2; //OK for OVERSAMPLING=0 tmp = ac1; tmp = (tmp*4 + x3)<> 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 = p + ((x1 + x2 + 3791) >> 4); }