[136] | 1 | /*
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| 2 | SCP1000 Barometric Pressure Sensor Display
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| 3 |
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| 4 | Shows the output of a Barometric Pressure Sensor on a
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| 5 | Uses the SPI library. For details on the sensor, see:
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| 6 | http://www.sparkfun.com/commerce/product_info.php?products_id=8161
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| 7 | http://www.vti.fi/en/support/obsolete_products/pressure_sensors/
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| 8 |
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| 9 | This sketch adapted from Nathan Seidle's SCP1000 example for PIC:
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| 10 | http://www.sparkfun.com/datasheets/Sensors/SCP1000-Testing.zip
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| 11 |
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| 12 | Circuit:
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| 13 | SCP1000 sensor attached to pins 6, 7, 10 - 13:
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| 14 | DRDY: pin 6
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| 15 | CSB: pin 7
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| 16 | MOSI: pin 11
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| 17 | MISO: pin 12
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| 18 | SCK: pin 13
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| 19 |
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| 20 | created 31 July 2010
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| 21 | modified 14 August 2010
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| 22 | by Tom Igoe
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| 23 | */
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| 24 |
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| 25 | // the sensor communicates using SPI, so include the library:
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| 26 | #include <SPI.h>
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| 27 |
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| 28 | //Sensor's memory register addresses:
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| 29 | const int PRESSURE = 0x1F; //3 most significant bits of pressure
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| 30 | const int PRESSURE_LSB = 0x20; //16 least significant bits of pressure
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| 31 | const int TEMPERATURE = 0x21; //16 bit temperature reading
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| 32 | const byte READ = 0b11111100; // SCP1000's read command
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| 33 | const byte WRITE = 0b00000010; // SCP1000's write command
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| 34 |
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| 35 | // pins used for the connection with the sensor
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| 36 | // the other you need are controlled by the SPI library):
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| 37 | const int dataReadyPin = 6;
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| 38 | const int chipSelectPin = 7;
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| 39 |
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| 40 | void setup() {
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| 41 | Serial.begin(9600);
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| 42 |
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| 43 | // start the SPI library:
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| 44 | SPI.begin();
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| 45 |
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| 46 | // initalize the data ready and chip select pins:
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| 47 | pinMode(dataReadyPin, INPUT);
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| 48 | pinMode(chipSelectPin, OUTPUT);
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| 49 |
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| 50 | //Configure SCP1000 for low noise configuration:
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| 51 | writeRegister(0x02, 0x2D);
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| 52 | writeRegister(0x01, 0x03);
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| 53 | writeRegister(0x03, 0x02);
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| 54 | // give the sensor time to set up:
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| 55 | delay(100);
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| 56 | }
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| 57 |
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| 58 | void loop() {
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| 59 | //Select High Resolution Mode
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| 60 | writeRegister(0x03, 0x0A);
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| 61 |
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| 62 | // don't do anything until the data ready pin is high:
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| 63 | if (digitalRead(dataReadyPin) == HIGH) {
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| 64 | //Read the temperature data
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| 65 | int tempData = readRegister(0x21, 2);
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| 66 |
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| 67 | // convert the temperature to celsius and display it:
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| 68 | float realTemp = (float)tempData / 20.0;
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| 69 | Serial.print("Temp[C]=");
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| 70 | Serial.print(realTemp);
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| 71 |
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| 72 |
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| 73 | //Read the pressure data highest 3 bits:
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| 74 | byte pressure_data_high = readRegister(0x1F, 1);
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| 75 | pressure_data_high &= 0b00000111; //you only needs bits 2 to 0
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| 76 |
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| 77 | //Read the pressure data lower 16 bits:
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| 78 | unsigned int pressure_data_low = readRegister(0x20, 2);
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| 79 | //combine the two parts into one 19-bit number:
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| 80 | long pressure = ((pressure_data_high << 16) | pressure_data_low) / 4;
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| 81 |
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| 82 | // display the temperature:
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| 83 | Serial.println("\tPressure [Pa]=" + String(pressure));
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| 84 | }
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| 85 | }
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| 86 |
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| 87 | //Read from or write to register from the SCP1000:
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| 88 | unsigned int readRegister(byte thisRegister, int bytesToRead ) {
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| 89 | byte inByte = 0; // incoming byte from the SPI
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| 90 | unsigned int result = 0; // result to return
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| 91 | Serial.print(thisRegister, BIN);
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| 92 | Serial.print("\t");
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| 93 | // SCP1000 expects the register name in the upper 6 bits
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| 94 | // of the byte. So shift the bits left by two bits:
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| 95 | thisRegister = thisRegister << 2;
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| 96 | // now combine the address and the command into one byte
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| 97 | byte dataToSend = thisRegister & READ;
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| 98 | Serial.println(thisRegister, BIN);
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| 99 | // take the chip select low to select the device:
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| 100 | digitalWrite(chipSelectPin, LOW);
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| 101 | // send the device the register you want to read:
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| 102 | SPI.transfer(dataToSend);
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| 103 | // send a value of 0 to read the first byte returned:
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| 104 | result = SPI.transfer(0x00);
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| 105 | // decrement the number of bytes left to read:
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| 106 | bytesToRead--;
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| 107 | // if you still have another byte to read:
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| 108 | if (bytesToRead > 0) {
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| 109 | // shift the first byte left, then get the second byte:
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| 110 | result = result << 8;
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| 111 | inByte = SPI.transfer(0x00);
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| 112 | // combine the byte you just got with the previous one:
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| 113 | result = result | inByte;
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| 114 | // decrement the number of bytes left to read:
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| 115 | bytesToRead--;
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| 116 | }
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| 117 | // take the chip select high to de-select:
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| 118 | digitalWrite(chipSelectPin, HIGH);
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| 119 | // return the result:
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| 120 | return(result);
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| 121 | }
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| 122 |
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| 123 |
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| 124 | //Sends a write command to SCP1000
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| 125 |
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| 126 | void writeRegister(byte thisRegister, byte thisValue) {
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| 127 |
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| 128 | // SCP1000 expects the register address in the upper 6 bits
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| 129 | // of the byte. So shift the bits left by two bits:
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| 130 | thisRegister = thisRegister << 2;
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| 131 | // now combine the register address and the command into one byte:
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| 132 | byte dataToSend = thisRegister | WRITE;
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| 133 |
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| 134 | // take the chip select low to select the device:
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| 135 | digitalWrite(chipSelectPin, LOW);
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| 136 |
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| 137 | SPI.transfer(dataToSend); //Send register location
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| 138 | SPI.transfer(thisValue); //Send value to record into register
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| 139 |
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| 140 | // take the chip select high to de-select:
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| 141 | digitalWrite(chipSelectPin, HIGH);
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| 142 | }
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| 143 |
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