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+===== ALPHA BMP180 =====
+==== 简介 ====
+BMP180是一款高精度、超低能耗的压力传感器，它是BMP085的升级版，代码兼容BMP085。
+==== 特点 ====
+  - IIC总线接口
+  - 自带温度传感器
+  - 完全校准
+==== 参数 ====
+^  压力范围  |  300 - 1100hPa  |
+^  电源电压  |  1.8 - 3.6V  |
+^  温度传感器  |  有  |
+^  通信接口  |  I2C  |
+^  低功耗模式精度  |  0.06hPa (0.5m)   |
+^  高精度模式精度  |  0.02hPa (0.17m)  |
+====图片参考====
+{{:ocrobot:alpha:bmp180:bmp180侧面-重调白平衡435-empty.jpg?nolink|}}
+{{:ocrobot:alpha:bmp180:bmp180正面-重调白平衡435-empty.jpg?nolink|}}
+==== 代码 ====
+<code cpp>
+/*
+  从BMP180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 BMP180_ADDRESS 0x77  // BMP180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bmp180GetTemperature(...)，它也同时用于bmp180GetPressure(...)
+// 所以Temperature(...)必须在Pressure(...)之前声明
+long b5;
+short temperature;
+long pressure;
+void setup()
+{
+  Serial.begin(9600);
+  Wire.begin();
+  bmp180Calibration();
+}
+void loop()
+{
+  temperature = bmp180GetTemperature(bmp180ReadUT());
+  pressure = bmp180GetPressure(bmp180ReadUP());
+  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BMP180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 bmp180Calibration()
+{
+  ac1 = bmp180ReadInt(0xAA);
+  ac2 = bmp180ReadInt(0xAC);
+  ac3 = bmp180ReadInt(0xAE);
+  ac4 = bmp180ReadInt(0xB0);
+  ac5 = bmp180ReadInt(0xB2);
+  ac6 = bmp180ReadInt(0xB4);
+  b1 = bmp180ReadInt(0xB6);
+  b2 = bmp180ReadInt(0xB8);
+  mb = bmp180ReadInt(0xBA);
+  mc = bmp180ReadInt(0xBC);
+  md = bmp180ReadInt(0xBE);
+}
+// 计算温度赋值给变量ut
+// 返回值的精度在0.1摄氏度
+short bmp180GetTemperature(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bmp180GetTemperature（...）需要使用，所以必须先调用。
+// 返回值以Pa为单位
+long bmp180GetPressure(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BMP180的'address'中读取一个字节
+char bmp180Read(unsigned char address)
+{
+  unsigned char data;
+  Wire.beginTransmission(BMP180_ADDRESS);
+  Wire.write(address);
+  Wire.endTransmission();
+  Wire.requestFrom(BMP180_ADDRESS, 1);
+  while(!Wire.available())  ;
+  return Wire.read();
+}
+// 从BMP180读取两个字节
+// 第一个字节是从'address'
+// 第二个字节是从'address'+1
+int bmp180ReadInt(unsigned char address)
+{
+  unsigned char msb, lsb;
+  Wire.beginTransmission(BMP180_ADDRESS);
+  Wire.write(address);
+  Wire.endTransmission();
+  Wire.requestFrom(BMP180_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 bmp180ReadUT()
+{
+  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(BMP180_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 = bmp180ReadInt(0xF6);
+  return ut;
+}
+// 读取未补偿的压力值
+unsigned long bmp180ReadUP()
+{
+  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(BMP180_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(BMP180_ADDRESS);
+  Wire.write(0xF6);
+  Wire.endTransmission();
+  Wire.requestFrom(BMP180_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;
+}
+</code>
+==== 下载 ====
+**数据手册：**
+{{:ocrobot:alpha:bmp180:bmp180.pdf|BMP180数据手册英文版}}
+**原理图：**
+{{:ocrobot:alpha:bmp180:alpha_bmp180_r2.pdf|ALPHA BMP180.pdf}}