/* SCP1000 Barometric Pressure Sensor Display Shows the output of a Barometric Pressure Sensor on a Uses the SPI library. For details on the sensor, see: http://www.sparkfun.com/commerce/product_info.php?products_id=8161 http://www.vti.fi/en/support/obsolete_products/pressure_sensors/ This sketch adapted from Nathan Seidle's SCP1000 example for PIC: http://www.sparkfun.com/datasheets/Sensors/SCP1000-Testing.zip Circuit: SCP1000 sensor attached to pins 6, 7, 10 - 13: DRDY: pin 6 CSB: pin 7 MOSI: pin 11 MISO: pin 12 SCK: pin 13 created 31 July 2010 modified 14 August 2010 by Tom Igoe */ // the sensor communicates using SPI, so include the library: #include //Sensor's memory register addresses: const int PRESSURE = 0x1F; // 3 most significant bits of pressure const int PRESSURE_LSB = 0x20; // 16 least significant bits of pressure const int TEMPERATURE = 0x21; // 16 bit temperature reading cont byte READ = 0b11111100; // SCP1000's read command const byte WRITE = 0b00000010; // SCP1000's write command // pins used for the connection with the sensor // the other you need are controlled by the SPI library): const int dataReadyPin = 6; const int chipSelectPin = 7; void setup() { Serial.begin(9600); // start the SPI library: SPI.begin(); // initalize the data ready and chip select pins: pinMode(dataReadyPin, INPUT); pinMode(chipSelectPin, OUTPUT); //Configure SCP1000 for low noise configuration: writeRegister(0x02, 0x2D); writeRegister(0x01, 0x03); writeRegister(0x03, 0x02); // give the sensor time to set up: delay(100); } void loop() { //Select High Resolution Mode writeRegister(0x03, 0x0A); // don't do anything until the data ready pin is high: if (digitalRead(dataReadyPin) == HIGH) { //Read the temperature data int tempData = readRegister(0x21, 2); // convert the temperature to celsius and display it: float realTemp = (float)tempData / 20.0; Serial.print("Temp[C]="); Serial.print(realTemp); //Read the pressure data highest 3 bits: byte pressure_data_high = readRegister(0x1F, 1); pressure_data_high &= 0b00000111; //you only needs bits 2 to 0 //Read the pressure data lower 16 bits: unsigned int pressure_data_low = readRegister(0x20, 2); //combine the two parts into one 19-bit number: long pressure = ((pressure_data_high << 16) | pressure_data_low)/4; // display the temperature: Serial.println("\tPressure [Pa]=" + String(pressure)); } } //Read from or write to register from the SCP1000: unsigned int readRegister(byte thisRegister, int bytesToRead ) { byte inByte = 0; // incoming byte from the SPI unsigned int result = 0; // result to return // SCP1000 expects the register name in the upper 6 bits // of the byte. So shift the bits left by two bits: thisRegister = thisRegister << 2; // now combine the address and the command into one byte dataToSend = thisRegister & READ; // take the chip select low to select the device: digitalWrite(chipSelectPin, LOW); // send the device the register you want to read: SPI.transfer(dataToSend); // send a value of 0 to read the first byte returned: result = SPI.transfer(0x00); // decrement the number of bytes left to read: bytesToRead--; // if you still have another byte to read: if (bytesToRead > 0) { // shift the first byte left, then get the second byte: result = result << 8; inByte = SPI.transfer(0x00); // combine the byte you just got with the previous one: result = result | inByte; // decrement the number of bytes left to read: bytesToRead--; } // take the chip select high to de-select: digitalWrite(chipSelectPin, HIGH); // return the result: return(result); } //Sends a write command to SCP1000 void writeRegister(byte thisRegister, byte thisValue) { // SCP1000 expects the register address in the upper 6 bits // of the byte. So shift the bits left by two bits: thisRegister = thisRegister << 2; // now combine the register address and the command into one byte: dataToSend = thisRegister | WRITE; // take the chip select low to select the device: digitalWrite(chipSelectPin, LOW); SPI.transfer(dataToSend); //Send register location SPI.transfer(thisValue); //Send value to record into register // take the chip select high to de-select: digitalWrite(chipSelectPin, HIGH); }