代码收藏家 STM32HAL库中HAL_I2C_Master_Transmit功能详解
最近开始使用stm32的模块来配置I2C，其中先主要分析一下HAL_I2C_Master_Transmit()库函数。
HAL_StatusTypeDef HAL_I2C_Master_Transmit(I2C_HandleTypeDef *hi2c, uint16_t DevAddress, uint8_t *pData,
uint16_t Size, uint32_t Timeout)
{
uint32_t tickstart;
if (hi2c->State == HAL_I2C_STATE_READY)
{
/* Process Locked */
__HAL_LOCK(hi2c);
/* Init tickstart for timeout management*/
tickstart = HAL_GetTick();
if (I2C_WaitOnFlagUntilTimeout(hi2c, I2C_FLAG_BUSY, SET, I2C_TIMEOUT_BUSY, tickstart) != HAL_OK)
{
return HAL_ERROR;
}
hi2c->State = HAL_I2C_STATE_BUSY_TX;
hi2c->Mode = HAL_I2C_MODE_MASTER;
hi2c->ErrorCode = HAL_I2C_ERROR_NONE;
/* Prepare transfer parameters */
hi2c->pBuffPtr = pData;
hi2c->XferCount = Size;
hi2c->XferISR = NULL;
/* Send Slave Address */
/* Set NBYTES to write and reload if hi2c->XferCount > MAX_NBYTE_SIZE and generate RESTART */
if (hi2c->XferCount > MAX_NBYTE_SIZE)
{
hi2c->XferSize = MAX_NBYTE_SIZE;
I2C_TransferConfig(hi2c, DevAddress, (uint8_t)hi2c->XferSize, I2C_RELOAD_MODE, //配置CR2 register
I2C_GENERATE_START_WRITE);
}
else
{
hi2c->XferSize = hi2c->XferCount;
I2C_TransferConfig(hi2c, DevAddress, (uint8_t)hi2c->XferSize, I2C_AUTOEND_MODE,
I2C_GENERATE_START_WRITE);
}
while (hi2c->XferCount > 0U)
{
/* Wait until TXIS flag is set */
if (I2C_WaitOnTXISFlagUntilTimeout(hi2c, Timeout, tickstart) != HAL_OK)
{
return HAL_ERROR;
}
/* Write data to TXDR */
hi2c->Instance->TXDR = *hi2c->pBuffPtr;
/* Increment Buffer pointer */
hi2c->pBuffPtr++;
hi2c->XferCount--;
hi2c->XferSize--;
if ((hi2c->XferCount != 0U) && (hi2c->XferSize == 0U))
{
/* Wait until TCR flag is set */
if (I2C_WaitOnFlagUntilTimeout(hi2c, I2C_FLAG_TCR, RESET, Timeout, tickstart) != HAL_OK)
{
return HAL_ERROR;
}
if (hi2c->XferCount > MAX_NBYTE_SIZE)
{
hi2c->XferSize = MAX_NBYTE_SIZE;
I2C_TransferConfig(hi2c, DevAddress, (uint8_t)hi2c->XferSize, I2C_RELOAD_MODE,
I2C_NO_STARTSTOP);
}
else
{
hi2c->XferSize = hi2c->XferCount;
I2C_TransferConfig(hi2c, DevAddress, (uint8_t)hi2c->XferSize, I2C_AUTOEND_MODE,
I2C_NO_STARTSTOP);
}
}
}
/* No need to Check TC flag, with AUTOEND mode the stop is automatically generated */
/* Wait until STOPF flag is set */
if (I2C_WaitOnSTOPFlagUntilTimeout(hi2c, Timeout, tickstart) != HAL_OK)
{
return HAL_ERROR;
}
/* Clear STOP Flag */
__HAL_I2C_CLEAR_FLAG(hi2c, I2C_FLAG_STOPF);
/* Clear Configuration Register 2 */
I2C_RESET_CR2(hi2c);
hi2c->State = HAL_I2C_STATE_READY;
hi2c->Mode = HAL_I2C_MODE_NONE;
/* Process Unlocked */
__HAL_UNLOCK(hi2c);
return HAL_OK;
}
else
{
return HAL_BUSY;
}
}首先函数四个形参分别是：1.指向i2c结构体的句柄.2.从机的设备地址。3.指向buffer的指针。4.需要发送数据的size总数 .5.延时。
接下来具体分析这个函数。
tickstart = HAL_GetTick();首先判断是ready状态，因为函数有超时判断，所以获取时钟。
if (I2C_WaitOnFlagUntilTimeout(hi2c, I2C_FLAG_BUSY, SET, I2C_TIMEOUT_BUSY, tickstart) != HAL_OK)
{
return HAL_ERROR;
}
接着看这个函数
static HAL_StatusTypeDef I2C_WaitOnFlagUntilTimeout(I2C_HandleTypeDef *hi2c, uint32_t Flag, FlagStatus Status,
uint32_t Timeout, uint32_t Tickstart)
{
while (__HAL_I2C_GET_FLAG(hi2c, Flag) == Status)
{
/* Check if an error is detected */
if (I2C_IsErrorOccurred(hi2c, Timeout, Tickstart) != HAL_OK)
{
return HAL_ERROR;
}
/* Check for the Timeout */
if (Timeout != HAL_MAX_DELAY)
{
if (((HAL_GetTick() - Tickstart) > Timeout) || (Timeout == 0U))
{
if ((__HAL_I2C_GET_FLAG(hi2c, Flag) == Status))
{
hi2c->ErrorCode |= HAL_I2C_ERROR_TIMEOUT;
hi2c->State = HAL_I2C_STATE_READY;
hi2c->Mode = HAL_I2C_MODE_NONE;
/* Process Unlocked */
__HAL_UNLOCK(hi2c);
return HAL_ERROR;
}
}
}
}
return HAL_OK;
}正如这个函数名字所示，它用来等待flag直到timeout。
我们更进一步分析一下这个函数：
while (__HAL_I2C_GET_FLAG(hi2c, Flag) == Status)
{
/* Check if an error is detected */
if (I2C_IsErrorOccurred(hi2c, Timeout, Tickstart) != HAL_OK)
{
return HAL_ERROR;
}
首先是这个while循环，这个内部条件是判断I2C的Flag状态是否是形参输入的status（在HAL_I2C_Master_Transmit（）函数中是判断是否busy），下面是源代码中的宏定义。
#define __HAL_I2C_GET_FLAG(__HANDLE__, __FLAG__) (((((__HANDLE__)->Instance->ISR) & \
(__FLAG__)) == (__FLAG__)) ? SET : RESET)接着看I2C_IsErrorOccurred(hi2c, Timeout, Tickstart)这个函数，这个函数总体较长，就不贴出来了，主要作用是判断有没有什么错误发生（其中包括从机是否应答ack）。
这个函数剩下的内容主要是判断是否超时。
接着我们看HAL_I2C_Master_Transmit（）函数中剩下部分：
hi2c->State = HAL_I2C_STATE_BUSY_TX;
hi2c->Mode = HAL_I2C_MODE_MASTER;
hi2c->ErrorCode = HAL_I2C_ERROR_NONE;
/* Prepare transfer parameters */
hi2c->pBuffPtr = pData;
hi2c->XferCount = Size;
hi2c->XferISR = NULL;这是往结构体里面的一下参数赋值，比较简单。
if (hi2c->XferCount > MAX_NBYTE_SIZE)
{
hi2c->XferSize = MAX_NBYTE_SIZE;
I2C_TransferConfig(hi2c, DevAddress, (uint8_t)hi2c->XferSize, I2C_RELOAD_MODE, //配置CR2 register
I2C_GENERATE_START_WRITE);
}
else
{
hi2c->XferSize = hi2c->XferCount;
I2C_TransferConfig(hi2c, DevAddress, (uint8_t)hi2c->XferSize, I2C_AUTOEND_MODE,
I2C_GENERATE_START_WRITE);
}
这个是根据xfercount是否大于maxsize来判断，其中I2C_TransferConfig函数用来配置CR2寄存器的内容。
具体内容如下：
static void I2C_TransferConfig(I2C_HandleTypeDef *hi2c, uint16_t DevAddress, uint8_t Size, uint32_t Mode,
uint32_t Request)
{
/* Check the parameters */
assert_param(IS_I2C_ALL_INSTANCE(hi2c->Instance));
assert_param(IS_TRANSFER_MODE(Mode));
assert_param(IS_TRANSFER_REQUEST(Request));
/* Declaration of tmp to prevent undefined behavior of volatile usage */
uint32_t tmp = ((uint32_t)(((uint32_t)DevAddress & I2C_CR2_SADD) | \
(((uint32_t)Size << I2C_CR2_NBYTES_Pos) & I2C_CR2_NBYTES) | \
(uint32_t)Mode | (uint32_t)Request) & (~0x80000000U));
/* update CR2 register */
MODIFY_REG(hi2c->Instance->CR2, \
((I2C_CR2_SADD | I2C_CR2_NBYTES | I2C_CR2_RELOAD | I2C_CR2_AUTOEND | \
(I2C_CR2_RD_WRN & (uint32_t)(Request >> (31U - I2C_CR2_RD_WRN_Pos))) | \
I2C_CR2_START | I2C_CR2_STOP)), tmp);
}根据设备地址，传输最大数据等参数，来配置CR2寄存器的值。
接下来我们看下一个while循环的内容：
while (hi2c->XferCount > 0U)
{
/* Wait until TXIS flag is set */
if (I2C_WaitOnTXISFlagUntilTimeout(hi2c, Timeout, tickstart) != HAL_OK)
{
return HAL_ERROR;
}
/* Write data to TXDR */
hi2c->Instance->TXDR = *hi2c->pBuffPtr;
/* Increment Buffer pointer */
hi2c->pBuffPtr++;
hi2c->XferCount--;
hi2c->XferSize--;
if ((hi2c->XferCount != 0U) && (hi2c->XferSize == 0U))
{
/* Wait until TCR flag is set */
if (I2C_WaitOnFlagUntilTimeout(hi2c, I2C_FLAG_TCR, RESET, Timeout, tickstart) != HAL_OK)
{
return HAL_ERROR;
}
if (hi2c->XferCount > MAX_NBYTE_SIZE)
{
hi2c->XferSize = MAX_NBYTE_SIZE;
I2C_TransferConfig(hi2c, DevAddress, (uint8_t)hi2c->XferSize, I2C_RELOAD_MODE,
I2C_NO_STARTSTOP);
}
else
{
hi2c->XferSize = hi2c->XferCount;
I2C_TransferConfig(hi2c, DevAddress, (uint8_t)hi2c->XferSize, I2C_AUTOEND_MODE,
I2C_NO_STARTSTOP);
}
}
}可以见到这个while的内容主要是实现了传输数据的功能，里面的一些函数在上文也有相关介绍。其中值得注意的是这几个if判断，用来判断要传输的数据大于Maxsize的情况。
/* Wait until STOPF flag is set */
if (I2C_WaitOnSTOPFlagUntilTimeout(hi2c, Timeout, tickstart) != HAL_OK)
{
return HAL_ERROR;
}
/* Clear STOP Flag */
__HAL_I2C_CLEAR_FLAG(hi2c, I2C_FLAG_STOPF);
/* Clear Configuration Register 2 */
I2C_RESET_CR2(hi2c);
hi2c->State = HAL_I2C_STATE_READY;
hi2c->Mode = HAL_I2C_MODE_NONE;
/* Process Unlocked */
__HAL_UNLOCK(hi2c);
return HAL_OK;
}
else
{
return HAL_BUSY;
}接下来的代码就不过多赘述。
作者：lmzyhhh
