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