stm32f4串口重定向hal库

### STM32F4 UART Redirection Using HAL Library Implementation For implementing UART redirection on the STM32F4 series microcontroller with the Hardware Abstraction Layer (HAL) library, configuring standard output to be redirected through a serial interface is essential. This allows printf statements or other console outputs to appear over UART instead of being lost as they would normally when running embedded code without such configuration. To achieve this functionality, initialization of the UART peripheral must occur first by setting up parameters like baud rate, word length, stop bits, parity control, hardware flow control, and mode (transmitter/receiver)[^1]. Following proper setup, `stdout` should then point towards the desired UART instance so that any calls made to functions like printf will send data out via the specified port rather than attempting to use non-existent system-level I/O facilities found within desktop operating systems. Below demonstrates how one might go about performing these tasks: #### Initialization Code Example ```c #include "stm32f4xx_hal.h" UART_HandleTypeDef huart1; void SystemClock_Config(void); static void MX_GPIO_Init(void); static void MX_USART1_UART_Init(void); int __io_putchar(int ch); /* Required for redirecting putchar */ int main(void){ HAL_Init(); SystemClock_Config(); MX_GPIO_Init(); MX_USART1_UART_Init(); while(1){ // Your application logic here. } } /* Function used to initialize USART1 */ static void MX_USART1_UART_Init(void){ huart1.Instance = USART1; huart1.Init.BaudRate = 115200; // Set Baud Rate value according to your needs huart1.Init.WordLength = UART_WORDLENGTH_8B;// Configure Word Length parameter huart1.Init.StopBits = UART_STOPBITS_1; // Choose number of Stop Bits huart1.Init.Parity = UART_PARITY_NONE; // Select Parity Control method huart1.Init.Mode = UART_MODE_TX_RX; // Enable Transmitter & Receiver modes huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE; // Disable HW Flow Control huart1.Init.OverSampling = UART_OVERSAMPLING_16; if(HAL_UART_Init(&huart1)!= HAL_OK){ // Initialize UART Peripheral Error_Handler(); // Handle errors appropriately } } ``` The above example initializes USART1 at a baudrate of 115200 bps configured for asynchronous communication where no hardware handshaking takes place between devices connected across TX/RX lines. The next step involves overriding `_write()` function which gets called internally whenever characters are sent from high level APIs including but not limited to printf(). By doing so, every character intended originally for display purposes now goes directly into transmit buffer associated with chosen UART channel before getting transmitted physically outside MCU pins. #### Redirect Putchar Definition ```c // Overriding weak symbol provided by newlib nano spec __attribute__((weak)) int _write(int fd, char *ptr, int len){ uint8_t i=0; for(i=0;i<len;i++){ ITM_SendChar(*ptr++); } return len; } ``` Alternatively, another approach could involve redefining `putchar()`. However, using `_write()` ensures compatibility even when different C libraries come into play during project development phases since most implementations rely upon it under-the-hood anyway. In conclusion, after completing both steps mentioned earlier—initializing relevant peripherals alongside altering default behavior tied specifically around sending bytes meant initially for terminal emulation—one achieves successful redirection capabilities allowing easier debugging sessions especially useful throughout early stages involved in firmware creation processes targeting ARM Cortex-M based platforms similar to those belonging inside STMicroelectronics' popular STM32 family members.