20 libmodbus软件包例程无法正常接收到从机返回的数据

发布于 2022-06-30 15:29:40 浏览：827 订阅该版

在RT-Thread Studio中使用libmodbus软件包内的官方例程，STM32H750作主机，ModbusSlave软件模拟从机

主机能正常发数据至从机，从机能够正常接收数据，且能正常返回数据，但主机无法正常接收到从机回返的数据
![Modbus Slave收发数据展示.jpg](https://oss-club.rt-thread.org/uploads/20220630/2d3761a23f2036a009d0f39cc287f0f7.jpg.webp "Modbus Slave收发数据展示.jpg")

修改后的libmodbus例程代码展示
```c
#include "modbus_rtu_test.h"
#include "modbus.h"
#include "stdio.h"
#include "string.h"
#include <rtthread.h>
#include <rtdevice.h>
#include <board.h>
#define RS485_RE GET_PIN(A, 10)

static void test_thread(void *param)
{
    uint16_t tab_reg[64] = {0};
    modbus_t *ctx = RT_NULL;
    ctx = modbus_new_rtu("/dev/uart1", 9600, 'N', 8, 1);
    modbus_set_debug(ctx, 1);
    modbus_rtu_set_serial_mode(ctx, MODBUS_RTU_RS485);
    modbus_rtu_set_rts(ctx, RS485_RE, MODBUS_RTU_RTS_UP);
    modbus_set_slave(ctx, 3);
    modbus_connect(ctx);
    modbus_set_response_timeout(ctx, 1, 1);
    int num = 0;
    while (1)
    {
        memset(tab_reg, 0, 64 * 2);
        int regs = modbus_read_registers(ctx, 0, 10, tab_reg);
        printf("-------------------------------------------\n");
        printf("[%4d][read num = %d]", num, regs);
        num++;
        int i;
        for (i = 0; i < 20; i++)
        {
            printf("<%#x>", tab_reg[i]);
        }
        printf("\n");
        printf("-------------------------------------------\n");
        rt_thread_mdelay(1000);
    }
    //7-关闭modbus端口
    modbus_close(ctx);

//8-释放modbus资源
    modbus_free(ctx);
}

static int rtu_test_init(void)
{
    rt_pin_mode(RS485_RE, PIN_MODE_OUTPUT);
    rt_thread_t tid;
    tid = rt_thread_create("test",
                           test_thread, RT_NULL,
                           2048,
                           12, 10);
    if (tid != RT_NULL)
        rt_thread_startup(tid);
    return RT_EOK;
}
INIT_APP_EXPORT(rtu_test_init);

```

串口配置-1
```c
/**
  * @brief USART1 Initialization Function
  * @param None
  * @retval None
  */
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 = 9600;
  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 */

}

/**
  * @brief USART2 Initialization Function
  * @param None
  * @retval None
  */
static void MX_USART2_UART_Init(void)
{

/* USER CODE BEGIN USART2_Init 0 */

/* USER CODE END USART2_Init 0 */

/* USER CODE BEGIN USART2_Init 1 */

/* USER CODE END USART2_Init 1 */
  huart2.Instance = USART2;
  huart2.Init.BaudRate = 115200;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart2.Init.ClockPrescaler = UART_PRESCALER_DIV1;
  huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
//    Error_Handler();
  }
  if (HAL_UARTEx_SetTxFifoThreshold(&huart2, UART_TXFIFO_THRESHOLD_1_8) != HAL_OK)
  {
//    Error_Handler();
  }
  if (HAL_UARTEx_SetRxFifoThreshold(&huart2, UART_RXFIFO_THRESHOLD_1_8) != HAL_OK)
  {
//    Error_Handler();
  }
  if (HAL_UARTEx_DisableFifoMode(&huart2) != HAL_OK)
  {
//    Error_Handler();
  }
  /* USER CODE BEGIN USART2_Init 2 */

/* USER CODE END USART2_Init 2 */

}
```

串口配置-2
```c
/**
* @brief UART MSP Initialization
* This function configures the hardware resources used in this example
* @param huart: UART handle pointer
* @retval None
*/
void HAL_UART_MspInit(UART_HandleTypeDef* huart)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};
  if(huart->Instance==USART1)
  {
  /* USER CODE BEGIN USART1_MspInit 0 */

/* USER CODE END USART1_MspInit 0 */

/** Initializes the peripherals clock
  */
    PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_USART1;
    PeriphClkInitStruct.Usart16ClockSelection = RCC_USART16CLKSOURCE_D2PCLK2;
    if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
    {
      Error_Handler();
    }

/* Peripheral clock enable */
    __HAL_RCC_USART1_CLK_ENABLE();

__HAL_RCC_GPIOA_CLK_ENABLE();
    __HAL_RCC_GPIOB_CLK_ENABLE();
    /**USART1 GPIO Configuration
    PA9     ------> USART1_TX
    PB15     ------> USART1_RX
    */
    GPIO_InitStruct.Pin = GPIO_PIN_9;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
    GPIO_InitStruct.Alternate = GPIO_AF7_USART1;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

GPIO_InitStruct.Pin = GPIO_PIN_15;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
    GPIO_InitStruct.Alternate = GPIO_AF4_USART1;
    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

/* USART1 interrupt Init */
    HAL_NVIC_SetPriority(USART1_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(USART1_IRQn);
  /* USER CODE BEGIN USART1_MspInit 1 */

/* USER CODE END USART1_MspInit 1 */
  }
  else if(huart->Instance==USART2)
  {
  /* USER CODE BEGIN USART2_MspInit 0 */

/* USER CODE END USART2_MspInit 0 */

/** Initializes the peripherals clock
  */
    PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_USART2;
    PeriphClkInitStruct.Usart234578ClockSelection = RCC_USART234578CLKSOURCE_D2PCLK1;
    if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
    {
      Error_Handler();
    }

/* Peripheral clock enable */
    __HAL_RCC_USART2_CLK_ENABLE();

__HAL_RCC_GPIOD_CLK_ENABLE();
    /**USART2 GPIO Configuration
    PD6     ------> USART2_RX
    PD5     ------> USART2_TX
    */
    GPIO_InitStruct.Pin = GPIO_PIN_6|GPIO_PIN_5;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
    GPIO_InitStruct.Alternate = GPIO_AF7_USART2;
    HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

/* USER CODE BEGIN USART2_MspInit 1 */

/* USER CODE END USART2_MspInit 1 */
  }

}

/**
* @brief UART MSP De-Initialization
* This function freeze the hardware resources used in this example
* @param huart: UART handle pointer
* @retval None
*/
void HAL_UART_MspDeInit(UART_HandleTypeDef* huart)
{
  if(huart->Instance==USART1)
  {
  /* USER CODE BEGIN USART1_MspDeInit 0 */

/* USER CODE END USART1_MspDeInit 0 */
    /* Peripheral clock disable */
    __HAL_RCC_USART1_CLK_DISABLE();

/**USART1 GPIO Configuration
    PA9     ------> USART1_TX
    PB15     ------> USART1_RX
    */
    HAL_GPIO_DeInit(GPIOA, GPIO_PIN_9);

HAL_GPIO_DeInit(GPIOB, GPIO_PIN_15);

/* USART1 interrupt DeInit */
    HAL_NVIC_DisableIRQ(USART1_IRQn);
  /* USER CODE BEGIN USART1_MspDeInit 1 */

/* USER CODE END USART1_MspDeInit 1 */
  }
  else if(huart->Instance==USART2)
  {
  /* USER CODE BEGIN USART2_MspDeInit 0 */

/* USER CODE END USART2_MspDeInit 0 */
    /* Peripheral clock disable */
    __HAL_RCC_USART2_CLK_DISABLE();

/**USART2 GPIO Configuration
    PD6     ------> USART2_RX
    PD5     ------> USART2_TX
    */
    HAL_GPIO_DeInit(GPIOD, GPIO_PIN_6|GPIO_PIN_5);

/* USER CODE BEGIN USART2_MspDeInit 1 */

/* USER CODE END USART2_MspDeInit 1 */
  }

}
```

报错信息
![2.jpg](https://oss-club.rt-thread.org/uploads/20220630/96b6d84dc9b0fa7d185adfa045631a96.jpg.webp "2.jpg")