STM32 I2C硬件配置库函数

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前言

一、I2C_DeInit函数

二、I2C_Init函数

三、I2C_StructInit函数

四、I2C_Cmd函数

五、I2C_GenerateSTART函数

六、I2C_GenerateSTOP函数

七、I2C_AcknowledgeConfig函数

八、I2C_SendData函数

九、I2C_ReceiveData函数

十、I2C_Send7bitAddress函数

十一、I2C状态监控功能

十二、标志位函数

12.1 I2C_GetFlagStatus函数

12.2 I2C_ClearFlag函数

12.3 I2C_GetITStatus函数

12.4 I2C_ClearITPendingBit函数

前言

本文介绍了I2C硬件配置常用的一些库函数。

一、I2C_DeInit函数

I2C_DeInit函数将外设 I2Cx 寄存器重设为缺省值。

二、I2C_Init函数

I2C_Init函数用于I2C的初始化。函数第二个参数是初始化的结构体。

I2C_Mode 用以设置 I2C 的模式。下表给出了该参数可取的值：

I2C_DutyCycle 用以设置 I2C 的占空比。下表给出了该参数可取的值：

注意：该参数只有在 I2C 工作在快速模式（时钟工作频率高于 100KHz）下才有意义。

I2C_OwnAddress1 该参数用来设置第一个设备自身地址，它可以是一个 7 位地址或者一个 10 位地址。

I2C_Ack 使能或者失能应答（ACK），下表给出了该参数可取的值：

I2C_AcknowledgedAddress 定义了应答 7 位地址还是 10 位地址。下表给出了该参数可取的值：

I2C_ClockSpeed 该参数用来设置时钟频率，这个值不能高于 400KHz。

三、I2C_StructInit函数

下表给出了 I2C_InitStruct 各个成员的缺省值：

四、I2C_Cmd函数

使能或失能I2C外设用I2C_Cmd函数来完成。

五、I2C_GenerateSTART函数

调用I2C_GenerateSTART函数，就可以生成起始条件。

程序源码：

/*** @brief  Generates I2Cx communication START condition.* @param  I2Cx: where x can be 1 or 2 to select the I2C peripheral.* @param  NewState: new state of the I2C START condition generation.*   This parameter can be: ENABLE or DISABLE.* @retval None.*/
void I2C_GenerateSTART(I2C_TypeDef* I2Cx, FunctionalState NewState)
{/* Check the parameters */assert_param(IS_I2C_ALL_PERIPH(I2Cx));assert_param(IS_FUNCTIONAL_STATE(NewState));if (NewState != DISABLE){/* Generate a START condition */I2Cx->CR1 |= CR1_START_Set;}else{/* Disable the START condition generation */I2Cx->CR1 &= CR1_START_Reset;}
}

如果 NewState 不等于 DISABLE，就把CR1寄存器的 START 位置1；否则，把 START 位清0.

START 位意义可以从手册里的寄存器描述中来了解：

START 置1

在从模式下是产生起始条件。
在主模式下是产生重复起始条件。

就是 START 这一位置1，产生起始条件。

六、I2C_GenerateSTOP函数

调用I2C_GenerateSTOP函数，生成终止条件。

程序源码：

/*** @brief  Generates I2Cx communication STOP condition.* @param  I2Cx: where x can be 1 or 2 to select the I2C peripheral.* @param  NewState: new state of the I2C STOP condition generation.*   This parameter can be: ENABLE or DISABLE.* @retval None.*/
void I2C_GenerateSTOP(I2C_TypeDef* I2Cx, FunctionalState NewState)
{/* Check the parameters */assert_param(IS_I2C_ALL_PERIPH(I2Cx));assert_param(IS_FUNCTIONAL_STATE(NewState));if (NewState != DISABLE){/* Generate a STOP condition */I2Cx->CR1 |= CR1_STOP_Set;}else{/* Disable the STOP condition generation */I2Cx->CR1 &= CR1_STOP_Reset;}
}

I2C_GenerateSTOP函数其实就是操作 CR1 的 STOP 位，查询手册中I2C寄存器的内容：

STOP 是产生停止条件的。STOP位置1，产生停止条件。

七、I2C_AcknowledgeConfig函数

I2C_AcknowledgeConfig函数是用来配置 CR1 的 ACK 这一位。就是配置，在收到一个字节后是否给从机应答。

程序源码：

/*** @brief  Enables or disables the specified I2C acknowledge feature.* @param  I2Cx: where x can be 1 or 2 to select the I2C peripheral.* @param  NewState: new state of the I2C Acknowledgement.*   This parameter can be: ENABLE or DISABLE.* @retval None.*/
void I2C_AcknowledgeConfig(I2C_TypeDef* I2Cx, FunctionalState NewState)
{/* Check the parameters */assert_param(IS_I2C_ALL_PERIPH(I2Cx));assert_param(IS_FUNCTIONAL_STATE(NewState));if (NewState != DISABLE){/* Enable the acknowledgement */I2Cx->CR1 |= CR1_ACK_Set;}else{/* Disable the acknowledgement */I2Cx->CR1 &= CR1_ACK_Reset;}
}

手册ACK寄存器描述：

ACK就是应答使能。STM32作为主机，在接收到一个字节后，是给从机应答还是非应答，就取决于ACK这一位。

在应答的时候：

如果ACK是1，就给从机应答。
如果ACK是0，就不给从机应答。

八、I2C_SendData函数

I2C_SendData函数用于写数据到数据寄存器DR。

程序源码：

/*** @brief  Sends a data byte through the I2Cx peripheral.* @param  I2Cx: where x can be 1 or 2 to select the I2C peripheral.* @param  Data: Byte to be transmitted..* @retval None*/
void I2C_SendData(I2C_TypeDef* I2Cx, uint8_t Data)
{/* Check the parameters */assert_param(IS_I2C_ALL_PERIPH(I2Cx));/* Write in the DR register the data to be sent */I2Cx->DR = Data;
}

分析源码，I2C_SendData函数实际就是把Data这个数据直接写入到DR寄存器。

手册DR寄存器描述：

DR数据寄存器用于存放接收到的数据或放置用于发送到总线的数据。在发送器模式下，当写一个字节至DR寄存器时，自动启动数据传输。一旦传输开始，也就是TxE=1，发送寄存器空，如果能及时把下一个需传输的数据写入DR寄存器，I2C模块将保持连续的数据流。

从上面可以看出两个信息：

一个是，写入DR，自动启动数据传输。也就是产生发送一个字节的波形。
另一个是，在上一个数据移位传输过程中，如果及时把下一个数据放在DR里等着，这样就能保持连续的数据流。

九、I2C_ReceiveData函数

I2C_ReceiveData函数用于读取DR数据，作为返回值。

程序源码：

/*** @brief  Returns the most recent received data by the I2Cx peripheral.* @param  I2Cx: where x can be 1 or 2 to select the I2C peripheral.* @retval The value of the received data.*/
uint8_t I2C_ReceiveData(I2C_TypeDef* I2Cx)
{/* Check the parameters */assert_param(IS_I2C_ALL_PERIPH(I2Cx));/* Return the data in the DR register */return (uint8_t)I2Cx->DR;
}

手册DR寄存器描述：

在接收器模式下，接收到的字节被拷贝到DR寄存器，这时就是RxNE=1，接收寄存器非空。在接收到下一个字节(RxNE=1)之前读出数据寄存器，即可实现连续的数据传送。

这里也可以看出两个信息：

一个是，接收移位完成时，收到的一个字节由移位寄存器转到数据寄存器。读取数据寄存器就能接收一个字节了。
另一个是，要在下一个字节收到之前，及时把上一个字节取走，防止数据覆盖。这样才能实现连续的数据流。

十、I2C_Send7bitAddress函数

I2C_Send7bitAddress函数是发送7位地址的专用函数。

程序源码：

/*** @brief  Transmits the address byte to select the slave device.* @param  I2Cx: where x can be 1 or 2 to select the I2C peripheral.* @param  Address: specifies the slave address which will be transmitted* @param  I2C_Direction: specifies whether the I2C device will be a*   Transmitter or a Receiver. This parameter can be one of the following values*     @arg I2C_Direction_Transmitter: Transmitter mode*     @arg I2C_Direction_Receiver: Receiver mode* @retval None.*/
void I2C_Send7bitAddress(I2C_TypeDef* I2Cx, uint8_t Address, uint8_t I2C_Direction)
{/* Check the parameters */assert_param(IS_I2C_ALL_PERIPH(I2Cx));assert_param(IS_I2C_DIRECTION(I2C_Direction));/* Test on the direction to set/reset the read/write bit */if (I2C_Direction != I2C_Direction_Transmitter){/* Set the address bit0 for read */Address |= OAR1_ADD0_Set;}else{/* Reset the address bit0 for write */Address &= OAR1_ADD0_Reset;}/* Send the address */I2Cx->DR = Address;
}

从源码可以看出，Address这个参数实际上也是通过DR发送的。只不过是Address参数在发送之前设置了Address最低位的读写位。

代码意思是：如果I2C_Direction不是发送，就把Address的最低位置1，也就是读；否则就把Address的最低位清0，也就是写。

在发送地址的时候，可以用一下这个函数。当然也可以手动设置最低位，调用I2C_SendData函数来发送地址。

十一、I2C状态监控功能

源码说明：

/*** @brief******************************************************************************************                         I2C State Monitoring Functions*                       ****************************************************************************************   * This I2C driver provides three different ways for I2C state monitoring*  depending on the application requirements and constraints:*        *  * 1) Basic state monitoring:*    Using I2C_CheckEvent() function:*    It compares the status registers (SR1 and SR2) content to a given event*    (can be the combination of one or more flags).*    It returns SUCCESS if the current status includes the given flags *    and returns ERROR if one or more flags are missing in the current status.*    - When to use:*      - This function is suitable for most applications as well as for startup *      activity since the events are fully described in the product reference manual *      (RM0008).*      - It is also suitable for users who need to define their own events.*    - Limitations:*      - If an error occurs (ie. error flags are set besides to the monitored flags),*        the I2C_CheckEvent() function may return SUCCESS despite the communication*        hold or corrupted real state. *        In this case, it is advised to use error interrupts to monitor the error*        events and handle them in the interrupt IRQ handler.*        *        @note *        For error management, it is advised to use the following functions:*          - I2C_ITConfig() to configure and enable the error interrupts (I2C_IT_ERR).*          - I2Cx_ER_IRQHandler() which is called when the error interrupt occurs.*            Where x is the peripheral instance (I2C1, I2C2 ...)*          - I2C_GetFlagStatus() or I2C_GetITStatus() to be called into I2Cx_ER_IRQHandler()*            in order to determine which error occurred.*          - I2C_ClearFlag() or I2C_ClearITPendingBit() and/or I2C_SoftwareResetCmd()*            and/or I2C_GenerateStop() in order to clear the error flag and source,*            and return to correct communication status.*            **  2) Advanced state monitoring:*     Using the function I2C_GetLastEvent() which returns the image of both status *     registers in a single word (uint32_t) (Status Register 2 value is shifted left *     by 16 bits and concatenated to Status Register 1).*     - When to use:*       - This function is suitable for the same applications above but it allows to*         overcome the limitations of I2C_GetFlagStatus() function (see below).*         The returned value could be compared to events already defined in the *         library (stm32f10x_i2c.h) or to custom values defined by user.*       - This function is suitable when multiple flags are monitored at the same time.*       - At the opposite of I2C_CheckEvent() function, this function allows user to*         choose when an event is accepted (when all events flags are set and no *         other flags are set or just when the needed flags are set like *         I2C_CheckEvent() function).*     - Limitations:*       - User may need to define his own events.*       - Same remark concerning the error management is applicable for this *         function if user decides to check only regular communication flags (and *         ignores error flags).*     **  3) Flag-based state monitoring:*     Using the function I2C_GetFlagStatus() which simply returns the status of *     one single flag (ie. I2C_FLAG_RXNE ...). *     - When to use:*        - This function could be used for specific applications or in debug phase.*        - It is suitable when only one flag checking is needed (most I2C events *          are monitored through multiple flags).*     - Limitations: *        - When calling this function, the Status register is accessed. Some flags are*          cleared when the status register is accessed. So checking the status*          of one Flag, may clear other ones.*        - Function may need to be called twice or more in order to monitor one *          single event.*            */

以上描述的是I2C的状态监控函数。

STM32有的状态可能会同时置多个标志位，