Arduino I2C + 气压传感器LPS25H

LPS25H是ST生产的MEMS数字气压传感器。主要特性有：

• 测量范围：260 ~ 1260 hPa绝对气压
• 分辨率：均方根1 Pa
• 工作电压：1.7 ~ 3.6 V
• 功耗：4μA（低分辨率模式）~25μA（高分辨率模式）
• 数据刷新频率：1 ~ 25 Hz可选择
• 接口：I2C，三线制/四线制SPI
• 内置温度补偿
• 内置24位ADC
• 内置先入先出（FIFO）存储器
• 封装：2.5 x 2.5 x 1.0 mm HCLGA-10L

管脚定义

• VDD：电源，1.7~3.6V
• GND：地
• VDD_IO：IO口供电脚，电压小于等于VDD
• GND_IO：IO口接地脚，需与GND相连
• Reserved：与GND相连
• CS：I2C接口（CS=1）选择，或SPI接口片选脚（CS=0）
• SCL/SPC：I2C接口或SPI接口的时钟线，通过CS脚选择
• SDA/SDI/SDIO：I2C接口或SPI接口的数据线
• SA0/SDO：I2C接口地址选择脚，或者SPI接口的数据线
• INT1：中断输出脚，可编程其触发条件，参见CTRL_REG4寄存器设置

与Arduino的连接

因为传感器IC大多工作在3.3V附近，因此干脆用工作于3.3V/8MHz版本的Arduino Pro Mini进行调试，避免了用UNO时接口电平转换的麻烦。采用I2C接口进行通讯。未利用INT1和FIFO的功能。

LPS25H　　Pro Mini 3.3V/8MHz

VDD <------> 3.3V

GND <------> GND

SCL <------>  A5 (SCL)

SDA <------> A4 (SDA)

测试代码

 /*
     Barometer based on LPS25H sensor and Arduino Pro Mini(3.3V)
 */

 #include <Wire.h>

 #define ADDRESS_LPS25H 0x5D
 #define CTRL_REG1 0x20
 #define CTRL_REG2 0x21
 #define PRESS_OUT_XL 0x28

 byte buffer[];

 boolean ready = false;
 int tempOut;
 long presOut;
 float tempVal;
 float presVal;

 void setup()
 {
     Wire.begin();
     Serial.begin();

     //power down the device (clean start)
     Wire.beginTransmission(ADDRESS_LPS25H);
     Wire.write(CTRL_REG1);
     Wire.write(0x00);
     Wire.endTransmission();

     //turn on the sensor, set the one-shot mode, and set the BDU bit
     Wire.beginTransmission(ADDRESS_LPS25H);
     Wire.write(CTRL_REG1);
     Wire.write(0x84);
     Wire.endTransmission();
 }

 void loop()
 {
     //run one-shot measurement
     Wire.beginTransmission(ADDRESS_LPS25H);
     Wire.write(CTRL_REG2);
     Wire.write(0x01);
     Wire.endTransmission();

     //wait until the measurement is completed
     while (ready == false)
     {
         delay(); //conversion time: ~37ms
         Wire.beginTransmission(ADDRESS_LPS25H);
         Wire.write(CTRL_REG2);
         Wire.endTransmission();
         Wire.requestFrom(ADDRESS_LPS25H, );
         if (Wire.read() == 0x00)
         {
             ready = true;
         }
         // Serial.println("waiting...");
     }

     //read the result
     Wire.beginTransmission(ADDRESS_LPS25H);
     Wire.write(PRESS_OUT_XL | 0x80); //read multiple bytes
     Wire.endTransmission();

     Wire.requestFrom(ADDRESS_LPS25H, );
     if (Wire.available() >= )
     {
         for (int i = ; i < ; i++)
         {
             buffer[i] = Wire.read();
         }
     }
     ready = false;

     //calculation
     presOut = (long(buffer[]) << ) | (long(buffer[]) << ) | long(buffer[]);
     presOut = (presOut << ) >> ; //PRESS_OUT_H/_L/_XL and is represented as 2’s complement
     presVal = presOut/4096.0;

     tempOut = (buffer[] << ) | buffer[];
     tempVal = 42.5 + tempOut/480.0;

     Serial.print(presVal); Serial.print(" hPa\t");
     Serial.print(tempVal); Serial.println(" `C");

     delay();
 } 

MCU每隔两秒测量一次气压和温度数据，并通过串口打印结果。

参考资料

LPS25H - STMicroelectronics