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首先看一下硬件连接图:
P1.6引脚接SCL,P1.7接SDA,VCC与GND接入模块上对应的就OK
注意~~~因为P1.6也同时连接着LED2,为了不影响IIC的通信,一定要把LED2的跳线帽拔掉,否则就会工作不正常。
我们把下面的代码放入Energia中进行编译,下载进入Launchpad。
- /*
- 从BMP085传感器读取温度与气压数据。
- 通过Serial.print命令以9600波特率发送至串口监视器。
- */
- #include <Wire.h>
- #define BMP085_ADDRESS 0x77 // BMP085的I2C地址
- const unsigned char OSS = 0; // 采样设置
- // 校准值
- int ac1;
- int ac2;
- int ac3;
- unsigned int ac4;
- unsigned int ac5;
- unsigned int ac6;
- int b1;
- int b2;
- int mb;
- int mc;
- int md;
- // b5用于计算bmp085GetTemperature(...),它也同时用于bmp085GetPressure(...)
- // 所以Temperature(...)必须在Pressure(...)之前声明
- long b5;
- short temperature;
- long pressure;
- void setup()
- {
- Serial.begin(9600);
- Wire.begin();
- bmp085Calibration();
- }
- void loop()
- {
- temperature = bmp085GetTemperature(bmp085ReadUT());
- pressure = bmp085GetPressure(bmp085ReadUP());
- Serial.print("Temperature: ");
- Serial.print(temperature, DEC);
- Serial.println(" *0.1 deg C");
- Serial.print("Pressure: ");
- Serial.print(pressure, DEC);
- Serial.println(" Pa");
- Serial.println();
- delay(1000);
- }
- // 存储所有的BMP085的校准值到全局变量
- // 校准值用来计算温度与气压
- // 这个函数应该放在程序的开头
- void bmp085Calibration()
- {
- ac1 = bmp085ReadInt(0xAA);
- ac2 = bmp085ReadInt(0xAC);
- ac3 = bmp085ReadInt(0xAE);
- ac4 = bmp085ReadInt(0xB0);
- ac5 = bmp085ReadInt(0xB2);
- ac6 = bmp085ReadInt(0xB4);
- b1 = bmp085ReadInt(0xB6);
- b2 = bmp085ReadInt(0xB8);
- mb = bmp085ReadInt(0xBA);
- mc = bmp085ReadInt(0xBC);
- md = bmp085ReadInt(0xBE);
- }
- // 计算温度赋值给变量ut
- // 返回值的精度在0.1摄氏度
- short bmp085GetTemperature(unsigned int ut)
- {
- long x1, x2;
- x1 = (((long)ut - (long)ac6)*(long)ac5) >> 15;
- x2 = ((long)mc << 11)/(x1 + md);
- b5 = x1 + x2;
- return ((b5 + 8)>>4);
- }
- // 计算压力
- // 校准值必须是已知的
- // B5在bmp085GetTemperature(...)需要使用,所以必须先调用。
- // 返回值以Pa为单位
- long bmp085GetPressure(unsigned long up)
- {
- long x1, x2, x3, b3, b6, p;
- unsigned long b4, b7;
- b6 = b5 - 4000;
- // 计算B3
- x1 = (b2 * (b6 * b6)>>12)>>11;
- x2 = (ac2 * b6)>>11;
- x3 = x1 + x2;
- b3 = (((((long)ac1)*4 + x3)<<OSS) + 2)>>2;
- // 计算B4
- x1 = (ac3 * b6)>>13;
- x2 = (b1 * ((b6 * b6)>>12))>>16;
- x3 = ((x1 + x2) + 2)>>2;
- b4 = (ac4 * (unsigned long)(x3 + 32768))>>15;
- b7 = ((unsigned long)(up - b3) * (50000>>OSS));
- if (b7 < 0x80000000)
- p = (b7<<1)/b4;
- else
- p = (b7/b4)<<1;
- x1 = (p>>8) * (p>>8);
- x1 = (x1 * 3038)>>16;
- x2 = (-7357 * p)>>16;
- p += (x1 + x2 + 3791)>>4;
- return p;
- }
- // 在BMP085的'address'中读取一个字节
- char bmp085Read(unsigned char address)
- {
- unsigned char data;
- Wire.beginTransmission(BMP085_ADDRESS);
- Wire.write(address);
- Wire.endTransmission();
- Wire.requestFrom(BMP085_ADDRESS, 1);
- while(!Wire.available()) ;
- return Wire.read();
- }
- // 从BMP085读取两个字节
- // 第一个字节是从'address'
- // 第二个字节是从'address'+1
- int bmp085ReadInt(unsigned char address)
- {
- unsigned char msb, lsb;
- Wire.beginTransmission(BMP085_ADDRESS);
- Wire.write(address);
- Wire.endTransmission();
- Wire.requestFrom(BMP085_ADDRESS, 2);
- while(Wire.available()<2);
- msb = Wire.read();
- lsb = Wire.read();
- return (int) msb<<8 | lsb;
- }
- // 读取未补偿的温度值
- unsigned int bmp085ReadUT()
- {
- unsigned int ut;
- // 在寄存器0xF4写入0x2E
- // 这个用来请求进行温度读取
- Wire.beginTransmission(BMP085_ADDRESS);
-
- Wire.write(0xF4);
-
- Wire.write(0x2E);
- Wire.endTransmission();
- // 至少等待4.5ms
- delay(5);
- // 从寄存器0xF6与0xF7读取两个字节
- ut = bmp085ReadInt(0xF6);
- return ut;
- }
- // 读取未补偿的压力值
- unsigned long bmp085ReadUP()
- {
- unsigned char msb, lsb, xlsb;
- unsigned long up = 0;
- // 写入0x34+(OSS<<6)到寄存器0xF4
- // 请求气压数据读取
- Wire.beginTransmission(BMP085_ADDRESS);
- Wire.write(0xF4);
- Wire.write(0x34 + (OSS<<6));
- Wire.endTransmission();
- // 等待转换,延迟时间依赖于OSS
- delay(2 + (3<<OSS));
- // 读取寄存器0xF6 (MSB), 0xF7 (LSB), and 0xF8 (XLSB)
- Wire.beginTransmission(BMP085_ADDRESS);
- Wire.write(0xF6);
- Wire.endTransmission();
- Wire.requestFrom(BMP085_ADDRESS, 3);
- // 等待数据变为可用
- while(Wire.available() < 3);
- msb = Wire.read();
- lsb = Wire.read();
- xlsb = Wire.read();
- up = (((unsigned long) msb << 16) | ((unsigned long) lsb << 8) | (unsigned long) xlsb) >> (8-OSS);
- return up;
- }
复制代码
下载程序的模式,TX RX的跳线帽一定要纵向链接。如图:
当下载好以后,我们需要把两个跳线帽拔下来,横向连接,这样子才能把数据通过串口发回电脑上,如图:
然后启动Energia的串口监视器,我们就能看到BMP085气压传感器返回的数据了。
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