STM32F072的I2C的使用方法

按官方提供的stm32f0xx_i2c.c中的说明部分做完初始化...

============================================================================

                     ##### How to use this driver #####

 ============================================================================

   [..]

   (#) Enable peripheral clock using RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2Cx, ENABLE)

       function for I2C1 or I2C2.

   (#) Enable SDA, SCL  and SMBA (when used) GPIO clocks using 

       RCC_AHBPeriphClockCmd() function. 

   (#) Peripherals alternate function: 

       (++) Connect the pin to the desired peripherals' Alternate 

            Function (AF) using GPIO_PinAFConfig() function.

       (++) Configure the desired pin in alternate function by:

            GPIO_InitStruct->GPIO_Mode = GPIO_Mode_AF

       (++) Select the type, OpenDrain and speed via  

            GPIO_PuPd, GPIO_OType and GPIO_Speed members

       (++) Call GPIO_Init() function.

   (#) Program the Mode, Timing , Own address, Ack and Acknowledged Address 

       using the I2C_Init() function.

   (#) Optionally you can enable/configure the following parameters without

       re-initialization (i.e there is no need to call again I2C_Init() function):

       (++) Enable the acknowledge feature using I2C_AcknowledgeConfig() function.

       (++) Enable the dual addressing mode using I2C_DualAddressCmd() function.

       (++) Enable the general call using the I2C_GeneralCallCmd() function.

       (++) Enable the clock stretching using I2C_StretchClockCmd() function.

       (++) Enable the PEC Calculation using I2C_CalculatePEC() function.

       (++) For SMBus Mode:

            (+++) Enable the SMBusAlert pin using I2C_SMBusAlertCmd() function.

   (#) Enable the NVIC and the corresponding interrupt using the function

       I2C_ITConfig() if you need to use interrupt mode.

   (#) When using the DMA mode 

      (++) Configure the DMA using DMA_Init() function.

      (++) Active the needed channel Request using I2C_DMACmd() function.

   (#) Enable the I2C using the I2C_Cmd() function.

   (#) Enable the DMA using the DMA_Cmd() function when using DMA mode in the 

       transfers. 

   [..]

   (@) When using I2C in Fast Mode Plus, SCL and SDA pin 20mA current drive capability

       must be enabled by setting the driving capability control bit in SYSCFG.

使用I2C_SendData发送数据，...，没反应？I2C_FLAG_TXE也一直不置位，说明并没有真正启动发送, Why?

仔细阅读I2C_CR2寄存器，发现有个NBYTES域，于是在发送数据之前把这个域填上，就能正常发送了。

例如需要发送01,02,03三个字节的数据，先初始化CR2，把NBYTES填3，然后启动START，往TXDR中依次写入01,02,03，发送成功！

接受也是同样的道理，NBYTES要填写需要接受的字节数。