STM32L1XX使用HAL_UART_Transmit_DMA发送串口数据

使用STM32CubeMX生成初始化代码。

问题：

HAL_UART_Transmit_DMA函数只能调用一次，第二次就返回状态HAL_UART_STATE_BUSY 0x02。

原因：

stm32l1xx_hal_uart.c开头有描述

(##) DMA Configuration if you need to use DMA process (HAL_UART_Transmit_DMA()

and HAL_UART_Receive_DMA() APIs):

(+++) Declare a DMA handle structure for the Tx/Rx channel.

(+++) Enable the DMAx interface clock.

(+++) Configure the declared DMA handle structure with the required

Tx/Rx parameters.

(+++) Configure the DMA Tx/Rx channel.

(+++) Associate the initialized DMA handle to the UART DMA Tx/Rx handle.

(+++) Configure the priority and enable the NVIC for the transfer complete

interrupt on the DMA Tx/Rx channel.

(+++) Configure the USARTx interrupt priority and enable the NVIC USART IRQ handle

(used for last byte sending completion detection in DMA non circular mode)

配置USARTx中断优先级，启用NVIC USART中断句柄（使用DMA非循环模式时，用来检测最后一个字节发送完毕）



默认 USART1的全局中断未Checked。

或者：

在发送结束的回调函数中，恢复uart的Ready状态。

void HAL_UART_TxHalfCpltCallback(UART_HandleTypeDef *huart)

{

//回调函数

huart->State=HAL_UART_STATE_READY;

}

下面附的是mbed-os的代码，它的UART_DMATransmitCplt函数直接复位Uart的状态了。

/**
* @brief DMA UART transmit process complete callback
* @param hdma: DMA handle
* @retval None
*/
01523 static void UART_DMATransmitCplt(DMA_HandleTypeDef *hdma)
{
UART_HandleTypeDef* huart = ( UART_HandleTypeDef* )((DMA_HandleTypeDef* )hdma)->Parent;
huart->TxXferCount = 0;

/* Disable the DMA transfer for transmit request by setting the DMAT bit
in the UART CR3 register */
huart->Instance->CR3 &= (uint32_t)~((uint32_t)USART_CR3_DMAT);

/* Wait for UART TC Flag */
if(UART_WaitOnFlagUntilTimeout(huart, UART_FLAG_TC, RESET, HAL_UART_TXDMA_TIMEOUTVALUE) != HAL_OK)
{
/* Timeout Occured */
huart->State = HAL_UART_STATE_TIMEOUT;
HAL_UART_ErrorCallback(huart);
}
else
{
/* No Timeout */
/* Check if a receive process is ongoing or not */
if(huart->State == HAL_UART_STATE_BUSY_TX_RX)
{
huart->State = HAL_UART_STATE_BUSY_RX;
}
else
{
huart->State = HAL_UART_STATE_READY;
}
HAL_UART_TxCpltCallback(huart);
}
}