SPI应用 用SPI总线读取气压传感器SCP1000的数据

Using SPI to read a Barometric Pressure Sensor

This example shows how to use the SPI (Serial Peripheral Interface) Communications Library to read data from a SCP1000 Barometric Pressure sensor. Please click here for more information on SPI.

Hardware Required  硬件准备

Arduino or Genuino board

SCP1000 Pressure Sensor Breakout Board

hook-up wires

Circuit 电路图

                       

image developed using Fritzing. For more circuit examples, see the Fritzing project page

Schematic 原理图

 

The SCP1000 barometric pressure sensor can read both air presure and temperature and report them via the SPI connection. For details of the control registers, see the SCP1000 data sheet.

 SCP1000传感器可测量气压和温度，并通过SPI总线与控制器连接

Code 程序代码

The code below starts out by setting the SCP1000's configuration registers in the setup(). In the main loop, it sets the sensor to read in high resolution mode, meaning that it will return a 19-bit value, for the pressure reading, and 16 bits for the temperature. The actual reading in degrees Celsius is the 16-bit result divided by 20.

使用时首先用setup()对SCP1000的配置寄存器进行设置。测量结果包含19位的气压值，16位的温度值。摄氏度等于16位数据除以20。

Then it reads the temperature's two bytes. Once it's got the temperature, it reads the pressure in two parts. First it reads the highest three bits, then the lower 16 bits. It combines these two into one single long integer by bit shifting the high bits then using a bitwise OR to combine them with the lower 16 bits. The actual pressure in Pascal is the 19-bit result divide by 4.

读取压力值时，先读高3位，再读低16位，然后通过移位组成19位的整数。帕斯卡数等于19位数据除以4。

/*
 SCP1000 Barometric Pressure Sensor Display

 Shows the output of a Barometric Pressure Sensor on a
 Uses the SPI library. For details on the sensor, see:
 http://www.sparkfun.com/commerce/product_info.php?products_id=8161
 http://www.vti.fi/en/support/obsolete_products/pressure_sensors/

 This sketch adapted from Nathan Seidle's SCP1000 example for PIC:
 http://www.sparkfun.com/datasheets/Sensors/SCP1000-Testing.zip

 Circuit:  SCP1000与控制板的接线
 SCP1000 sensor attached to pins 6, 7, 10 - 13:
 DRDY: pin 6   dataReadyPin
 CSB: pin 7     chipSelectPin
 MOSI: pin 11
 MISO: pin 12
 SCK: pin 13

 created 31 July 2010
 modified 14 August 2010
 by Tom Igoe
 */
// the sensor communicates using SPI, so include the library:
#include <SPI.h>

//Sensor's memory register addresses:

const int PRESSURE = 0x1F;      //3 most significant bits of pressure
const int PRESSURE_LSB = 0x20;  //16 least significant bits of pressure
const int TEMPERATURE = 0x21;   //16 bit temperature reading
const byte READ = 0b11111100;     // SCP1000's read command  SCP1000的读指令
const byte WRITE = 0b00000010;   // SCP1000's write command  SCP1000的写指令

// pins used for the connection with the sensor
// the other you need are controlled by the SPI library):
const int dataReadyPin = 6;
const int chipSelectPin = 7;
void setup() 

{
  Serial.begin(9600);
  // start the SPI library:
  SPI.begin();

  // initalize the  data ready and chip select pins:
  pinMode(dataReadyPin, INPUT);   //数据准备信号来自传感器
  pinMode(chipSelectPin, OUTPUT);   //芯片选择信号来自控制器

  //Configure SCP1000 for low noise configuration:
  writeRegister(0x02, 0x2D);
  writeRegister(0x01, 0x03);
  writeRegister(0x03, 0x02);
  // give the sensor time to set up:
  delay(100);
}


void loop()

 {
  //Select High Resolution Mode  
  writeRegister(0x03, 0x0A);

  // don't do anything until the data ready pin is high:
  if (digitalRead(dataReadyPin) == HIGH) 

{
    //Read the temperature data
    int tempData = readRegister(0x21, 2);  //2个字节
    // convert the temperature to celsius and display it:
    float realTemp = (float)tempData / 20.0;   //转换为摄氏温度
    Serial.print("Temp[C]=");
    Serial.print(realTemp);


    //Read the pressure data highest 3 bits:
    byte  pressure_data_high = readRegister(0x1F, 1);
    pressure_data_high &= 0b00000111;    //you only needs bits 2 to 0

    //Read the pressure data lower 16 bits:
    unsigned int  pressure_data_low = readRegister(0x20, 2);
    //combine the two parts into one 19-bit number:  并转换为帕斯卡
    long pressure = ((pressure_data_high << 16) | pressure_data_low) / 4;
    // display the temperature:
    Serial.println("	Pressure [Pa]=" + String(pressure));
  }
}

//Read from or write to register from the SCP1000:
unsigned int  readRegister(byte thisRegister, int bytesToRead)   //读SCP1000的寄存器

{
  byte inByte = 0;           // incoming byte from the SPI
  unsigned int result = 0;   // result to return
  Serial.print(thisRegister, BIN);
  Serial.print("	");
  // SCP1000 expects the register name in the upper 6 bits
  // of the byte. So shift the bits left by two bits:
  thisRegister = thisRegister << 2;
  // now combine the address and the command into one byte
  byte dataToSend = thisRegister & READ;   //  READ是读指令0b11111100
  Serial.println(thisRegister, BIN);
  // take the chip select low to select the device:
  digitalWrite(chipSelectPin, LOW);
  // send the device the register you want to read:
  SPI.transfer(dataToSend);    //传送寄存器地址
  // send a value of 0 to read the first byte returned:
  result = SPI.transfer(0x00);   //传送0x00以得到第1个字节的数据
  // decrement the number of bytes left to read:
  bytesToRead--;
  // if you still have another byte to read:
  if (bytesToRead > 0) 

{
    // shift the first byte left, then get the second byte:
    result = result << 8;
    inByte = SPI.transfer(0x00);
    // combine the byte you just got with the previous one:
    result = result | inByte;
    // decrement the number of bytes left to read:
    bytesToRead--;
  }
  // take the chip select high to de-select:
  digitalWrite(chipSelectPin, HIGH);
  // return the result:
  return (result);
}

//Sends a write command to SCP1000
void writeRegister(byte thisRegister, byte thisValue)    //写SCP1000的寄存器

{
  // SCP1000 expects the register address in the upper 6 bits
  // of the byte. So shift the bits left by two bits:
  thisRegister = thisRegister << 2;
  // now combine the register address and the command into one byte:
  byte dataToSend = thisRegister | WRITE;  // WRITE是写指令0b00000010
  // take the chip select low to select the device:
  digitalWrite(chipSelectPin, LOW);
  SPI.transfer(dataToSend);    //Send register location
  SPI.transfer(thisValue);       //Send value to record into register
  // take the chip select high to de-select:
  digitalWrite(chipSelectPin, HIGH);
}