root / arduino-1.0 / libraries / SPI / examples / BarometricPressureSensor / BarometricPressureSensor.ino @ 58d82c77
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1 | 58d82c77 | Tom Mullins | /* |
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2 | SCP1000 Barometric Pressure Sensor Display |
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3 | |||
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 | |||
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 | |||
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 | |||
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 | |||
25 | // the sensor communicates using SPI, so include the library: |
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26 | #include <SPI.h> |
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27 | |||
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 | |||
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 | |||
40 | void setup() { |
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41 | Serial.begin(9600); |
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42 | |||
43 | // start the SPI library: |
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44 | SPI.begin(); |
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45 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
72 | |||
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 | |||
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 | |||
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 | |||
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 | |||
123 | |||
124 | //Sends a write command to SCP1000 |
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125 | |||
126 | void writeRegister(byte thisRegister, byte thisValue) { |
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127 | |||
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 | |||
134 | // take the chip select low to select the device: |
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135 | digitalWrite(chipSelectPin, LOW); |
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136 | |||
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 | |||
140 | // take the chip select high to de-select: |
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141 | digitalWrite(chipSelectPin, HIGH); |
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142 | } |