上一篇测评的是EXTI外部中断，本次来一步步增加UART打印功能。从DK板子的用户手册得知，PA9与PA10用于VCP的收发。
查看原理图：
查看数据手册得知:
配置USART1外设的PIN即Tx与Rx：
点击保存，CubeIDE内置的CubeMX会自动生成代码：
static void MX_USART1_UART_Init(void)
{
/* USER CODE BEGIN USART1_Init 0 */
/* USER CODE END USART1_Init 0 */
/* USER CODE BEGIN USART1_Init 1 */
/* USER CODE END USART1_Init 1 */
huart1.Instance = USART1;
huart1.Init.BaudRate = 115200;
huart1.Init.WordLength = UART_WORDLENGTH_8B;
huart1.Init.StopBits = UART_STOPBITS_1;
huart1.Init.Parity = UART_PARITY_NONE;
huart1.Init.Mode = UART_MODE_TX_RX;
huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart1.Init.OverSampling = UART_OVERSAMPLING_16;
huart1.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
huart1.Init.ClockPrescaler = UART_PRESCALER_DIV1;
huart1.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
if (HAL_UART_Init(&huart1) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_SetTxFifoThreshold(&huart1, UART_TXFIFO_THRESHOLD_1_8) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_SetRxFifoThreshold(&huart1, UART_RXFIFO_THRESHOLD_1_8) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_DisableFifoMode(&huart1) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN USART1_Init 2 */
/* USER CODE END USART1_Init 2 */
}
但是编译会报错，后来发现是虽然生成了代码，但是新增加的UART模块的驱动并没有自动拷贝过来，需要手动拖拽到CubeIDE的工程树里面。
现在UART已经编译没有错误了，下面增加PRINTF打印功能：
首先包含头文件：
其次在UART句柄声明后，添加如下代码：
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
#ifdef __GNUC__
#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif
PUTCHAR_PROTOTYPE
{
HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, HAL_MAX_DELAY);
return ch;
}
/* USER CODE END 0 */
Opening and parsing file: ST-LINK_GDB_server_a12616.srec
Memory Programming ...
File : ST-LINK_GDB_server_a12616.srec
Size : 19.38 KB
Address : 0x08000000
Erasing memory corresponding to segment 0:
Erasing internal memory sectors [0 9]
Download in Progress:
File download complete
Time elapsed during download operation: 00:00:00.574
Verifying ...
Download verified successfully
Shutting down...
Exit.
实物按键测试：
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