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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