UART Serial Port Software Development Process (Based on MCU)

1. Preparation Work

• Hardware

• Confirm the MCU serial port (USART1, UART4, etc.);

• Confirm the “pins” (TX: transmit pin, RX: receive pin). For example: PA9, PA10;

• TX connects to RX, RX connects to TX, GND connects to GND;

Note: Ensure common ground (GND), which is essential for the signal circuit and level reference.

• Protocol Format: Ensure that the baud rate, data bits, stop bits, parity bits, and other configurations are completely consistent;

2. MCU Program Initialization (Using STM32 HAL Library as an Example)

• Initialization Configuration

• Enable Peripheral Clock: First, enable the clock for UART and the corresponding GPIO.

__HAL_RCC_USART1_CLK_ENABLE();__HAL_RCC_GPIOA_CLK_ENABLE();

• GPIO Configuration Initialization: Set the TX pin to “Alternate Function Push-Pull Output”, and the RX pin to “Floating Input or Pull-Up Input”.

GPIO_InitStruct.Pin = GPIO_PIN_9;GPIO_InitStruct.Mode = GPIO_MODE_AF_PP; // Alternate Function Push-Pull OutputGPIO_InitStruct.Pull = GPIO_NOPULL;GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

• UART Configuration Parameter Initialization:

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; // Transmit and Receive Modehuart1.Init.HwFlowCtl = UART_HWCONTROL_NONE; // No Hardware Flow ControlHAL_UART_Init(&huart1);

• Data Transmission and Reception Mode Selection (Three Core Methods)

• Blocking Mode (Polling):

• Send: HAL_UART_Transmit(&huart1, pData, Size, Timeout)

• Receive: HAL_UART_Receive(&huart1, pData, Size, Timeout)

• Characteristics: The CPU will wait until the send/receive is complete or times out. Simple but inefficient, as the CPU cannot perform other tasks while waiting, suitable for simple applications.

• Interrupt Mode:

• Send: HAL_UART_Transmit_IT(&huart1, pData, Size)

• Receive: HAL_UART_Receive_IT(&huart1, pData, Size)

• Characteristics: The CPU returns immediately after starting the transmission, and an interrupt is triggered upon completion. High efficiency, allowing the CPU to handle other tasks during data transmission.

• Key: It is necessary to rewrite the interrupt callback functions HAL_UART_TxCpltCallback and HAL_UART_RxCpltCallback to handle the logic after sending or receiving is complete.

• DMA Mode (Direct Memory Access):

• Send: HAL_UART_Transmit_DMA(&huart1, pData, Size)

• Receive: HAL_UART_Receive_DMA(&huart1, pData, Size)

• Characteristics: The DMA controller transfers data in the background without CPU involvement, achieving the highest efficiency, especially suitable for large data transfers or high-speed communication.

• Key: Callback functions are also required. Can be combined with idle interrupts to receive variable-length data: enable idle interrupts, which will trigger when a frame of data is received and the bus is idle, allowing processing of the data received in the DMA buffer.

3. Common Software Issues

• Can only send once/unable to receive continuously: When using interrupt reception, HAL_UART_Receive_IT must be called again after one reception is complete to start the next reception;

• Data Loss: Data is received too quickly, and the CPU cannot process it in time. Optimize code efficiency or use DMA + idle interrupts + circular buffer to receive data;

• Program Freezes:

• May be due to improper interrupt handling, leading to frequent interrupts. Check interrupt priority;

• Timeout setting is too long in blocking mode.

Summary