STM32duino: I2C

关于I2C，官方的例子如下：

// --------------------------------------
// i2c_scanner
//
// Version 1
//    This program (or code that looks like it)
//    can be found in many places.
//    For example on the Arduino.cc forum.
//    The original author is not know.
// Version 2, Juni 2012, Using Arduino 1.0.1
//     Adapted to be as simple as possible by Arduino.cc user Krodal
// Version 3, Feb 26  2013
//    V3 by louarnold
// Version 4, March 3, 2013, Using Arduino 1.0.3
//    by Arduino.cc user Krodal.
//    Changes by louarnold removed.
//    Scanning addresses changed from 0...127 to 1...119,
//    according to the i2c scanner by Nick Gammon
//    http://www.gammon.com.au/forum/?id=10896
// Version 5, March 28, 2013
//    As version 4, but address scans now to 127.
//    A sensor seems to use address 120.
// 
//
// This sketch tests the standard 7-bit addresses
// Devices with higher bit address might not be seen properly.
//

#include 


void setup()
{
  Wire.begin();

  Serial.begin(9600);
  Serial.println("\nI2C Scanner");
}


void loop()
{
  byte error, address;
  int nDevices;

  Serial.println("Scanning...");

  nDevices = 0;
  for(address = 1; address < 127; address++ ) 
  {
    // The i2c_scanner uses the return value of
    // the Write.endTransmisstion to see if
    // a device did acknowledge to the address.
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0)
    {
      Serial.print("I2C device found at address 0x");
      if (address<16) 
        Serial.print("0");
      Serial.print(address,HEX);
      Serial.println("  !");

      nDevices++;
    }
    else if (error==4) 
    {
      Serial.print("Unknow error at address 0x");
      if (address<16) 
        Serial.print("0");
      Serial.println(address,HEX);
    }    
  }
  if (nDevices == 0)
    Serial.println("No I2C devices found\n");
  else
    Serial.println("done\n");

  delay(5000);           // wait 5 seconds for next scan
}

没有什么悬念，这和Arduino使用的方法也没有什么不同。这个默认使用的是I2C1（也就是PB6 PB7）。如果硬件上接错了，需要使用I2C2(也就是PB10 PB11)的话怎么办呢？

Wire的定义和实现在这里
C:\Program Files (x86)\Arduino\hardware\Arduino_STM32\STM32F1\libraries\Wire\Wire.cpp中

HardWire Wire(1);

所以当你要使用I2C2的时候，只需要在自己的代码中如下定义，就可以使用Wire1（I2C2）了。

HardWire Wire1(2);

但是有一点，像一些现成的库基于I2C的OLED显示屏的Adafuit_SSD1306库中默认使用的I2C是Wire而不是Wire1。那么直接改Wire.cpp要比较改第三方库方便了。

HardWire Wire(2);

这样硬件上接的I2C2的设备可以直接使用了。