SPI应用 用SPI总线读取气压传感器SCP1000的数据

  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:  SCP1000与控制板的接线
 13  SCP1000 sensor attached to pins 6, 7, 10 - 13:
 14  DRDY: pin 6   dataReadyPin
 15  CSB: pin 7     chipSelectPin
 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 // the sensor communicates using SPI, so include the library:
 25 #include <SPI.h>
 26 
 27 //Sensor‘s memory register addresses:
 28 
 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  SCP1000的读指令
 33 const byte WRITE = 0b00000010;   // SCP1000‘s write command  SCP1000的写指令
 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 void setup() 
 40 
 41 {
 42   Serial.begin(9600);
 43   // start the SPI library:
 44   SPI.begin();
 45 
 46   // initalize the  data ready and chip select pins:
 47   pinMode(dataReadyPin, INPUT);   //数据准备信号来自传感器
 48   pinMode(chipSelectPin, OUTPUT);   //芯片选择信号来自控制器
 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 
 59 void loop()
 60 
 61  {
 62   //Select High Resolution Mode  
 63   writeRegister(0x03, 0x0A);
 64 
 65   // don‘t do anything until the data ready pin is high:
 66   if (digitalRead(dataReadyPin) == HIGH) 
 67 
 68 {
 69     //Read the temperature data
 70     int tempData = readRegister(0x21, 2);  //2个字节
 71     // convert the temperature to celsius and display it:
 72     float realTemp = (float)tempData / 20.0;   //转换为摄氏温度
 73     Serial.print("Temp[C]=");
 74     Serial.print(realTemp);
 75 
 76 
 77     //Read the pressure data highest 3 bits:
 78     byte  pressure_data_high = readRegister(0x1F, 1);
 79     pressure_data_high &= 0b00000111;    //you only needs bits 2 to 0
 80 
 81     //Read the pressure data lower 16 bits:
 82     unsigned int  pressure_data_low = readRegister(0x20, 2);
 83     //combine the two parts into one 19-bit number:  并转换为帕斯卡
 84     long pressure = ((pressure_data_high << 16) | pressure_data_low) / 4;
 85     // display the temperature:
 86     Serial.println("\tPressure [Pa]=" + String(pressure));
 87   }
 88 }
 89 
 90 //Read from or write to register from the SCP1000:
 91 unsigned int  readRegister(byte thisRegister, int bytesToRead)   //读SCP1000的寄存器
 92 
 93 {
 94   byte inByte = 0;           // incoming byte from the SPI
 95   unsigned int result = 0;   // result to return
 96   Serial.print(thisRegister, BIN);
 97   Serial.print("\t");
 98   // SCP1000 expects the register name in the upper 6 bits
 99   // of the byte. So shift the bits left by two bits:
100   thisRegister = thisRegister << 2;
101   // now combine the address and the command into one byte
102   byte dataToSend = thisRegister & READ;   //  READ是读指令0b11111100
103   Serial.println(thisRegister, BIN);
104   // take the chip select low to select the device:
105   digitalWrite(chipSelectPin, LOW);
106   // send the device the register you want to read:
107   SPI.transfer(dataToSend);    //传送寄存器地址
108   // send a value of 0 to read the first byte returned:
109   result = SPI.transfer(0x00);   //传送0x00以得到第1个字节的数据
110   // decrement the number of bytes left to read:
111   bytesToRead--;
112   // if you still have another byte to read:
113   if (bytesToRead > 0) 
114 
115 {
116     // shift the first byte left, then get the second byte:
117     result = result << 8;
118     inByte = SPI.transfer(0x00);
119     // combine the byte you just got with the previous one:
120     result = result | inByte;
121     // decrement the number of bytes left to read:
122     bytesToRead--;
123   }
124   // take the chip select high to de-select:
125   digitalWrite(chipSelectPin, HIGH);
126   // return the result:
127   return (result);
128 }
129 
130 //Sends a write command to SCP1000
131 void writeRegister(byte thisRegister, byte thisValue)    //写SCP1000的寄存器
132 
133 {
134   // SCP1000 expects the register address in the upper 6 bits
135   // of the byte. So shift the bits left by two bits:
136   thisRegister = thisRegister << 2;
137   // now combine the register address and the command into one byte:
138   byte dataToSend = thisRegister | WRITE;  // WRITE是写指令0b00000010
139   // take the chip select low to select the device:
140   digitalWrite(chipSelectPin, LOW);
141   SPI.transfer(dataToSend);    //Send register location
142   SPI.transfer(thisValue);       //Send value to record into register
143   // take the chip select high to de-select:
144   digitalWrite(chipSelectPin, HIGH);
145 }
146 
147