/* 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 and Altitude This function is optimized so the main host don´t need to wait You can call this function in your main loop Maximun data output frequency 100Hz 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 get_altitude() : return altitude in meters Internal functions: calculate() : Calculate Temperature and Pressure (temperature compensated) in real units */ #include #include "AP_Baro_MS5611.h" #define MS5611_CS A2 // Chip select pin (provisional) #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 // Maximun resolution #define CMD_CONVERT_D2_OSR4096 0x58 // Maximun resolution uint8_t MS5611_SPI_read(byte reg) { byte dump; uint8_t return_value; byte addr = reg; // | 0x80; // Set most significant bit digitalWrite(MS5611_CS, LOW); dump = SPI.transfer(addr); return_value = SPI.transfer(0); digitalWrite(MS5611_CS, HIGH); return(return_value); } uint16_t MS5611_SPI_read_16bits(byte reg) { byte dump,byteH,byteL; uint16_t return_value; byte addr = reg; // | 0x80; // Set most significant bit digitalWrite(MS5611_CS, LOW); dump = SPI.transfer(addr); byteH = SPI.transfer(0); byteL = SPI.transfer(0); digitalWrite(MS5611_CS, HIGH); return_value = ((uint16_t)byteH<<8) | (byteL); return(return_value); } uint32_t MS5611_SPI_read_ADC() { byte dump,byteH,byteM,byteL; uint32_t return_value; byte addr = 0x00; digitalWrite(MS5611_CS, LOW); dump = SPI.transfer(addr); 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 MS5611_SPI_write(byte reg) { byte dump; digitalWrite(MS5611_CS, LOW); dump = SPI.transfer(reg); digitalWrite(MS5611_CS, HIGH); } // The conversion proccess takes 8.2ms since the command uint8_t AP_Baro_MS5611::MS5611_Ready() { if ((millis()-MS5611_timer)>10) // wait for more than 10ms return(1); else return(0); } // Public Methods ////////////////////////////////////////////////////////////// // SPI should be initialized externally void AP_Baro_MS5611::init() { pinMode(MS5611_CS, OUTPUT); // Chip select Pin MS5611_SPI_write(CMD_MS5611_RESET); delay(4); // We read the factory calibration C1 = MS5611_SPI_read_16bits(CMD_MS5611_PROM_C1); C2 = MS5611_SPI_read_16bits(CMD_MS5611_PROM_C2); C3 = MS5611_SPI_read_16bits(CMD_MS5611_PROM_C3); C4 = MS5611_SPI_read_16bits(CMD_MS5611_PROM_C4); C5 = MS5611_SPI_read_16bits(CMD_MS5611_PROM_C5); C6 = MS5611_SPI_read_16bits(CMD_MS5611_PROM_C6); //Send a command to read Temp first MS5611_SPI_write(CMD_CONVERT_D2_OSR4096); MS5611_timer = millis(); MS5611_State = 1; Temp=0; Press=0; } // 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... uint8_t AP_Baro_MS5611::read() { uint8_t result = 0; if (MS5611_State == 1){ if (MS5611_Ready()){ D2=MS5611_SPI_read_ADC(); // On state 1 we read temp MS5611_State++; MS5611_SPI_write(CMD_CONVERT_D1_OSR4096); // Command to read pressure MS5611_timer = millis(); } }else{ if (MS5611_State == 5){ if (MS5611_Ready()){ D1=MS5611_SPI_read_ADC(); calculate(); MS5611_State = 1; // Start again from state = 1 MS5611_SPI_write(CMD_CONVERT_D2_OSR4096); // Command to read temperature MS5611_timer = millis(); result = 1; // New pressure reading } }else{ if (MS5611_Ready()){ D1=MS5611_SPI_read_ADC(); calculate(); MS5611_State++; MS5611_SPI_write(CMD_CONVERT_D1_OSR4096); // Command to read pressure MS5611_timer = millis(); result = 1; // New pressure reading } } } return(result); } // Calculate Temperature and compensated Pressure in real units (Celsius degrees*100, mbar*100). void AP_Baro_MS5611::calculate() { int32_t dT; long long TEMP; // 64 bits long long OFF; long long SENS; long long P; // Formulas from manufacturer datasheet // TODO: optimization with shift operations... (shift operations works well on 64 bits variables?) // We define parameters as 64 bits to prevent overflow on operations dT = D2-((long)C5*256); TEMP = 2000 + ((long long)dT * C6)/8388608; OFF = (long long)C2 * 65536 + ((long long)C4 * dT ) / 128; SENS = (long long)C1 * 32768 + ((long long)C3 * dT) / 256; /* if (TEMP < 2000){ // second order temperature compensation long long T2 = (long long)dT*dT / 2147483648; long long Aux_64 = (TEMP-2000)*(TEMP-2000); long long OFF2 = 5*Aux_64/2; long long SENS2 = 5*Aux_64/4; TEMP = TEMP - T2; OFF = OFF - OFF2; SENS = SENS - SENS2; } */ P = (D1*SENS/2097152 - OFF)/32768; Temp = TEMP; Press = P; } uint32_t AP_Baro_MS5611::get_pressure() { return(Press); } uint16_t AP_Baro_MS5611::get_temperature() { return(Temp); } // Return altitude using the standard 1013.25 mbar at sea level reference float AP_Baro_MS5611::get_altitude() { float tmp_float; float Altitude; tmp_float = (Press / 101325.0); tmp_float = pow(tmp_float, 0.190295); Altitude = 44330 * (1.0 - tmp_float); return (Altitude); }