stm32hal库函数485通信例子

以下是一个基于STM32 HAL库函数的485通信例子：

#include "stm32f4xx_hal.h"

#define USART_TX_PIN GPIO_PIN_9
#define USART_RX_PIN GPIO_PIN_10
#define USART_PORT GPIOA
#define USART_HANDLE huart2
#define RS485_DIR_PIN GPIO_PIN_8
#define RS485_DIR_PORT GPIOA

UART_HandleTypeDef USART_HANDLE;

void RS485_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct;
  
  __HAL_RCC_GPIOA_CLK_ENABLE();
  
  // Configure USART GPIOs
  GPIO_InitStruct.Pin = USART_TX_PIN | USART_RX_PIN;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
  GPIO_InitStruct.Alternate = GPIO_AF7_USART2;
  HAL_GPIO_Init(USART_PORT, &GPIO_InitStruct);
  
  // Configure RS485 direction pin
  GPIO_InitStruct.Pin = RS485_DIR_PIN;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
  HAL_GPIO_Init(RS485_DIR_PORT, &GPIO_InitStruct);
  
  // Configure USART
  __HAL_RCC_USART2_CLK_ENABLE();
  
  USART_HANDLE.Instance = USART2;
  USART_HANDLE.Init.BaudRate = 9600;
  USART_HANDLE.Init.WordLength = UART_WORDLENGTH_8B;
  USART_HANDLE.Init.StopBits = UART_STOPBITS_1;
  USART_HANDLE.Init.Parity = UART_PARITY_NONE;
  USART_HANDLE.Init.Mode = UART_MODE_TX_RX;
  USART_HANDLE.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  USART_HANDLE.Init.OverSampling = UART_OVERSAMPLING_16;
  USART_HANDLE.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  USART_HANDLE.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  HAL_UART_Init(&USART_HANDLE);
}

void RS485_SendData(uint8_t *data, uint16_t len)
{
  // Set direction to transmit
  HAL_GPIO_WritePin(RS485_DIR_PORT, RS485_DIR_PIN, GPIO_PIN_SET);
  
  // Send data
  HAL_UART_Transmit(&USART_HANDLE, data, len, HAL_MAX_DELAY);
  
  // Wait for transmission to complete
  HAL_UART_Transmit(&USART_HANDLE, NULL, 0, HAL_MAX_DELAY);
  
  // Set direction to receive
  HAL_GPIO_WritePin(RS485_DIR_PORT, RS485_DIR_PIN, GPIO_PIN_RESET);
}

void RS485_ReceiveData(uint8_t *data, uint16_t len)
{
  // Set direction to receive
  HAL_GPIO_WritePin(RS485_DIR_PORT, RS485_DIR_PIN, GPIO_PIN_RESET);
  
  // Receive data
  HAL_UART_Receive(&USART_HANDLE, data, len, HAL_MAX_DELAY);
}

这个例子中，我们使用了USART2作为RS485通信的串口。在初始化函数`RS485_Init`中，我们配置了USART2的GPIO引脚和串口参数。在发送数据函数`RS485_SendData`中，我们先将RS485的方向引脚设置为发送模式，然后使用HAL库函数`HAL_UART_Transmit`发送数据。在数据发送完成后，我们再次使用`HAL_UART_Transmit`发送一个空数据，等待数据发送完成。最后，我们将RS485的方向引脚设置为接收模式。在接收数据函数`RS485_ReceiveData`中，我们先将RS485的方向引脚设置为接收模式，然后使用HAL库函数`HAL_UART_Receive`接收数据。