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tigoetigoe
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Modified Barometric Pressure Sensor to make it easier for beginners to understand.
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‎libraries/SPI/examples/BarometricPressureSensor/BarometricPressureSensor.pde‎

Lines changed: 107 additions & 115 deletions
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/*
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SCP1000 Barometric Pressure Sensor Display
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Shows the output of a Barometric Pressure Sensor on a
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Uses the SPI library. For details on the sensor, see:
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http://www.sparkfun.com/commerce/product_info.php?products_id=8161
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http://www.vti.fi/en/support/obsolete_products/pressure_sensors/
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This sketch adapted from Nathan Seidle's SCP1000 example for PIC:
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http://www.sparkfun.com/datasheets/Sensors/SCP1000-Testing.zip
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Circuit:
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SCP1000 sensor attached to pins 6, 7, 10 - 13:
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DRDY: pin 6
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CSB: pin 7
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MOSI: pin 11 MOSI, MISO, SCK pins are different depending on the
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MISO: pin 12 board type. See your board's documentation for details
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SCK: pin 13
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created 31 July 2010
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by Tom Igoe
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*/
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SCP1000 Barometric Pressure Sensor Display
4+
5+
Shows the output of a Barometric Pressure Sensor on a
6+
Uses the SPI library. For details on the sensor, see:
7+
http://www.sparkfun.com/commerce/product_info.php?products_id=8161
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http://www.vti.fi/en/support/obsolete_products/pressure_sensors/
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This sketch adapted from Nathan Seidle's SCP1000 example for PIC:
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http://www.sparkfun.com/datasheets/Sensors/SCP1000-Testing.zip
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Circuit:
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SCP1000 sensor attached to pins 6, 7, 10 - 13:
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DRDY: pin 6
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CSB: pin 7
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MOSI: pin 11
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MISO: pin 12
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SCK: pin 13
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created 31 July 2010
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modified 14 August 2010
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by Tom Igoe
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*/
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// the sensor communicates using SPI, so include the library:
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#include <SPI.h>
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//Sensor's memory register addresses:
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const int PRESSURE = 0x1F; //3 most significant bits of pressure
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const int PRESSURE_LSB = 0x20; //16 least significant bits of pressure
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const int TEMPERATURE = 0x21; //16 bit temperature reading
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const int PRESSURE = 0x1F; // 3 most significant bits of pressure
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const int PRESSURE_LSB = 0x20; // 16 least significant bits of pressure
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const int TEMPERATURE = 0x21; // 16 bit temperature reading
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cont byte READ = 0b11111100; // SCP1000's read command
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const byte WRITE = 0b00000010; // SCP1000's write command
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// pins used for the connection with the sensor
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// the other you need are controlled by the SPI library):
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const int dataReadyPin = 6;
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const int chipSelectPin = 7;
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void setup() {
38-
Serial.begin(9600);
42+
Serial.begin(9600);
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40-
// start the SPI library:
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SPI.begin();
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// start the SPI library:
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SPI.begin();
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// initalize the data ready and chip select pins:
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pinMode(dataReadyPin, INPUT);
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pinMode(chipSelectPin, OUTPUT);
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// initalize the data ready and chip select pins:
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pinMode(dataReadyPin, INPUT);
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pinMode(chipSelectPin, OUTPUT);
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47-
//Configure SCP1000 for low noise configuration:
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writeRegister(0x02, 0x2D);
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writeRegister(0x01, 0x03);
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writeRegister(0x03, 0x02);
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// give the sensor time to set up:
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delay(100);
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//Configure SCP1000 for low noise configuration:
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writeRegister(0x02, 0x2D);
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writeRegister(0x01, 0x03);
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writeRegister(0x03, 0x02);
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// give the sensor time to set up:
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delay(100);
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}
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void loop() {
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//Select High Resolution Mode
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writeRegister(0x03, 0x0A);
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//Select High Resolution Mode
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writeRegister(0x03, 0x0A);
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// don't do anything until the data ready pin is high:
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if (digitalRead(dataReadyPin) == HIGH) {
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//Read the temperature data
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int tempData = readRegister(0x21, 2);
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// don't do anything until the data ready pin is high:
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if (digitalRead(dataReadyPin) == HIGH) {
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//Read the temperature data
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int tempData = readRegister(0x21, 2);
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// convert the temperature to celsius and display it:
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float realTemp = (float)tempData / 20.0;
66-
Serial.print("Temp[C]=");
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Serial.print(realTemp);
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// convert the temperature to celsius and display it:
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float realTemp = (float)tempData / 20.0;
70+
Serial.print("Temp[C]=");
71+
Serial.print(realTemp);
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//Read the pressure data highest 3 bits:
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byte pressure_data_high = readRegister(0x1F, 1);
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pressure_data_high &= 0b00000111; //you only needs bits 2 to 0
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//Read the pressure data highest 3 bits:
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byte pressure_data_high = readRegister(0x1F, 1);
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pressure_data_high &= 0b00000111; //you only needs bits 2 to 0
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//Read the pressure data lower 16 bits:
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unsigned int pressure_data_low = readRegister(0x20, 2);
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//combine the two parts into one 19-bit number:
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long pressure = ((pressure_data_high << 16) | pressure_data_low)/4;
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//Read the pressure data lower 16 bits:
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unsigned int pressure_data_low = readRegister(0x20, 2);
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//combine the two parts into one 19-bit number:
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long pressure = ((pressure_data_high << 16) | pressure_data_low)/4;
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// display the temperature:
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Serial.println("\tPressure [Pa]=" + String(pressure));
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}
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// display the temperature:
84+
Serial.println("\tPressure [Pa]=" + String(pressure));
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}
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}
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//Sends a write command to SCP1000
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void writeRegister(byte registerName, byte registerValue) {
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// SCP1000 expects the reguster name in the upper 6 bits
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// of the byte:
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registerName <<= 2;
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// command goes in the lower two bits:
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registerName |= 0b00000010; //Write command
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// take the chip select low to select the device:
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digitalWrite(chipSelectPin, LOW);
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SPI.transfer(registerName); //Send register location
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SPI.transfer(registerValue); //Send value to record into register
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// take the chip select high to de-select:
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digitalWrite(chipSelectPin, HIGH); //Select SPI device
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//Read from or write to register from the SCP1000:
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unsigned int readRegister(byte thisRegister, int bytesToRead ) {
90+
byte inByte = 0; // incoming byte from the SPI
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unsigned int result = 0; // result to return
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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+
dataToSend = thisRegister & READ;
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// 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);
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// decrement the number of bytes left to read:
106+
bytesToRead--;
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// if you still have another byte to read:
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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);
101121
}
102122

103123

104-
//Read register from the SCP1000:
105-
unsigned int readRegister(byte registerName, int numBytes) {
106-
byte inByte = 0; // incoming from the SPI read
107-
unsigned int result = 0; // result to return
108-
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// SCP1000 expects the reguster name in the upper 6 bits
110-
// of the byte:
111-
registerName <<= 2;
112-
// command goes in the lower two bits:
113-
registerName &= 0b11111100; //Read command
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// take the chip select low to select the device:
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digitalWrite(chipSelectPin, LOW);
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// send the device the register you want to read:
118-
int command = SPI.transfer(registerName);
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// send a value of 0 to read the forst byte returned:
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inByte = SPI.transfer(0x00);
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// if there's more than one byte returned,
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// shift the first byte then get the second byte:
124-
switch(numBytes) {
125-
case 1:
126-
result = inByte;
127-
break;
128-
case 2:
129-
result = inByte << 8;
130-
inByte = SPI.transfer(0x00);
131-
result = result |inByte;
132-
break;
133-
}
134-
// take the chip select high to de-select:
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digitalWrite(chipSelectPin, HIGH);
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// return the result:
137-
return(result);
138-
}
139-
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124+
//Sends a write command to SCP1000
146125

126+
void writeRegister(byte thisRegister, byte thisValue) {
147127

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+
dataToSend = thisRegister | WRITE;
148133

134+
// take the chip select low to select the device:
135+
digitalWrite(chipSelectPin, LOW);
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137+
SPI.transfer(dataToSend); //Send register location
138+
SPI.transfer(thisValue); //Send value to record into register
150139

140+
// take the chip select high to de-select:
141+
digitalWrite(chipSelectPin, HIGH);
142+
}

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