/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- /* * APM_MS5611.cpp - Arduino Library for MS5611-01BA01 absolute pressure sensor * Code by Jose Julio, Pat Hickey and Jordi Muñoz. 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 standard SPI port * Chip Select pin: Analog2 (provisional until Jordi defines the pin)!! * * Variables: * Temp : Calculated temperature (in Celsius degrees * 100) * Press : Calculated pressure (in mbar units * 100) * * * Methods: * init() : Initialization and sensor reset * read() : Read sensor data and _calculate Temperature, Pressure * This function is optimized so the main host don´t need to wait * You can call this function in your main loop * Maximum data output frequency 100Hz - this allows maximum oversampling in the chip ADC * It returns a 1 if there are new data. * get_pressure() : return pressure in mbar*100 units * get_temperature() : return temperature in celsius degrees*100 units * * Internal functions: * _calculate() : Calculate Temperature and Pressure (temperature compensated) in real units * * */ #include #include #include "AP_Baro_MS5611.h" /* on APM v.24 MS5661_CS is PG1 (Arduino pin 40) */ #define MS5611_CS 40 #define CMD_MS5611_RESET 0x1E #define CMD_MS5611_PROM_Setup 0xA0 #define CMD_MS5611_PROM_C1 0xA2 #define CMD_MS5611_PROM_C2 0xA4 #define CMD_MS5611_PROM_C3 0xA6 #define CMD_MS5611_PROM_C4 0xA8 #define CMD_MS5611_PROM_C5 0xAA #define CMD_MS5611_PROM_C6 0xAC #define CMD_MS5611_PROM_CRC 0xAE #define CMD_CONVERT_D1_OSR4096 0x48 // Maximum resolution (oversampling) #define CMD_CONVERT_D2_OSR4096 0x58 // Maximum resolution (oversampling) uint32_t volatile AP_Baro_MS5611::_s_D1; uint32_t volatile AP_Baro_MS5611::_s_D2; uint8_t volatile AP_Baro_MS5611::_d1_count; uint8_t volatile AP_Baro_MS5611::_d2_count; uint8_t AP_Baro_MS5611::_state; uint32_t AP_Baro_MS5611::_timer; bool volatile AP_Baro_MS5611::_updated; uint8_t AP_Baro_MS5611::_spi_read(uint8_t reg) { uint8_t return_value; uint8_t addr = reg; // | 0x80; // Set most significant bit digitalWrite(MS5611_CS, LOW); SPI.transfer(addr); // discarded return_value = SPI.transfer(0); digitalWrite(MS5611_CS, HIGH); return return_value; } uint16_t AP_Baro_MS5611::_spi_read_16bits(uint8_t reg) { uint8_t byteH, byteL; uint16_t return_value; uint8_t addr = reg; // | 0x80; // Set most significant bit digitalWrite(MS5611_CS, LOW); SPI.transfer(addr); // discarded byteH = SPI.transfer(0); byteL = SPI.transfer(0); digitalWrite(MS5611_CS, HIGH); return_value = ((uint16_t)byteH<<8) | (byteL); return return_value; } uint32_t AP_Baro_MS5611::_spi_read_adc() { uint8_t byteH,byteM,byteL; uint32_t return_value; uint8_t addr = 0x00; digitalWrite(MS5611_CS, LOW); SPI.transfer(addr); // discarded byteH = SPI.transfer(0); byteM = SPI.transfer(0); byteL = SPI.transfer(0); digitalWrite(MS5611_CS, HIGH); return_value = (((uint32_t)byteH)<<16) | (((uint32_t)byteM)<<8) | (byteL); return return_value; } void AP_Baro_MS5611::_spi_write(uint8_t reg) { digitalWrite(MS5611_CS, LOW); SPI.transfer(reg); // discarded digitalWrite(MS5611_CS, HIGH); } // Public Methods ////////////////////////////////////////////////////////////// // SPI should be initialized externally bool AP_Baro_MS5611::init( AP_PeriodicProcess *scheduler ) { scheduler->suspend_timer(); pinMode(MS5611_CS, OUTPUT); // Chip select Pin digitalWrite(MS5611_CS, HIGH); delay(1); _spi_write(CMD_MS5611_RESET); delay(4); // We read the factory calibration // The on-chip CRC is not used C1 = _spi_read_16bits(CMD_MS5611_PROM_C1); C2 = _spi_read_16bits(CMD_MS5611_PROM_C2); C3 = _spi_read_16bits(CMD_MS5611_PROM_C3); C4 = _spi_read_16bits(CMD_MS5611_PROM_C4); C5 = _spi_read_16bits(CMD_MS5611_PROM_C5); C6 = _spi_read_16bits(CMD_MS5611_PROM_C6); //Send a command to read Temp first _spi_write(CMD_CONVERT_D2_OSR4096); _timer = micros(); _state = 0; Temp=0; Press=0; _s_D1 = 0; _s_D2 = 0; _d1_count = 0; _d2_count = 0; scheduler->resume_timer(); scheduler->register_process( AP_Baro_MS5611::_update ); // wait for at least one value to be read while (!_updated) ; healthy = true; return true; } // Read the sensor. This is a state machine // We read one time Temperature (state=1) and then 4 times Pressure (states 2-5) // temperature does not change so quickly... void AP_Baro_MS5611::_update(uint32_t tnow) { // Throttle read rate to 100hz maximum. // note we use 9500us here not 10000us // the read rate will end up at exactly 100hz because the Periodic Timer fires at 1khz if (tnow - _timer < 9500) { return; } _timer = tnow; if (_state == 0) { _s_D2 += _spi_read_adc(); // On state 0 we read temp _d2_count++; if (_d2_count == 32) { // we have summed 32 values. This only happens // when we stop reading the barometer for a long time // (more than 1.2 seconds) _s_D2 >>= 1; _d2_count = 16; } _state++; _spi_write(CMD_CONVERT_D1_OSR4096); // Command to read pressure } else { _s_D1 += _spi_read_adc(); _d1_count++; if (_d1_count == 128) { // we have summed 128 values. This only happens // when we stop reading the barometer for a long time // (more than 1.2 seconds) _s_D1 >>= 1; _d1_count = 64; } _state++; _updated = true; // New pressure reading if (_state == 5) { _spi_write(CMD_CONVERT_D2_OSR4096); // Command to read temperature _state = 0; } else { _spi_write(CMD_CONVERT_D1_OSR4096); // Command to read pressure } } } uint8_t AP_Baro_MS5611::read() { bool updated = _updated; if (updated) { uint32_t sD1, sD2; uint8_t d1count, d2count; // we need to disable interrupts to access // _s_D1 and _s_D2 as they are not atomic uint8_t oldSREG = SREG; cli(); sD1 = _s_D1; _s_D1 = 0; sD2 = _s_D2; _s_D2 = 0; d1count = _d1_count; _d1_count = 0; d2count = _d2_count; _d2_count = 0; _updated = false; SREG = oldSREG; if (d1count != 0) { D1 = ((float)sD1) / d1count; } if (d2count != 0) { D2 = ((float)sD2) / d2count; } _pressure_samples = d1count; _raw_press = D1; _raw_temp = D2; } _calculate(); if (updated) { _last_update = millis(); } return updated ? 1 : 0; } // Calculate Temperature and compensated Pressure in real units (Celsius degrees*100, mbar*100). void AP_Baro_MS5611::_calculate() { float dT; float TEMP; float OFF; float SENS; float P; // Formulas from manufacturer datasheet // sub -20c temperature compensation is not included // we do the calculations using floating point // as this is much faster on an AVR2560, and also allows // us to take advantage of the averaging of D1 and D1 over // multiple samples, giving us more precision dT = D2-(((uint32_t)C5)<<8); TEMP = (dT * C6)/8388608; OFF = C2 * 65536.0 + (C4 * dT) / 128; SENS = C1 * 32768.0 + (C3 * dT) / 256; if (TEMP < 0) { // second order temperature compensation when under 20 degrees C float T2 = (dT*dT) / 0x80000000; float Aux = TEMP*TEMP; float OFF2 = 2.5*Aux; float SENS2 = 1.25*Aux; TEMP = TEMP - T2; OFF = OFF - OFF2; SENS = SENS - SENS2; } P = (D1*SENS/2097152 - OFF)/32768; Temp = TEMP + 2000; Press = P; } float AP_Baro_MS5611::get_pressure() { return Press; } float AP_Baro_MS5611::get_temperature() { // callers want the temperature in 0.1C units return Temp/10; } int32_t AP_Baro_MS5611::get_raw_pressure() { return _raw_press; } int32_t AP_Baro_MS5611::get_raw_temp() { return _raw_temp; }