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STM32F446RE board UART2 reception interrupt does not behave as expected

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PPopo
Senior

‎2019-12-14 09:11 AM

Hello,

I'm trying to get used with the HAL APIs by doing an exercises with USART of the mentioned board.

The exercise is a simple one in which I try to send a character from my PC terminal using Tera Term and if this character is 'a' I want the MCU on the board to light up the user LED.

I have configured USART2 module with CubeMx. The generated configuration code for the USART2 module is this:

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;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN USART2_Init 2 */
 
  /* USER CODE END USART2_Init 2 */
 
}

This is the full main.c code:

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; Copyright (c) 2019 STMicroelectronics.
  * All rights reserved.</center></h2>
  *
  * This software component is licensed by ST under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
  * License. You may obtain a copy of the License at:
  *                        opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
  */
/* USER CODE END Header */
 
/* Includes ------------------------------------------------------------------*/
#include "main.h"
 
#define TRUE 1
#define FALSE 0
 
uint8_t data_buffer[100];
uint8_t recvd_data;
uint32_t count=0;
uint8_t reception_complete = FALSE;
 
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
 
/* USER CODE END Includes */
 
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
 
/* USER CODE END PTD */
 
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
 
/* USER CODE END PD */
 
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
 
/* USER CODE END PM */
 
/* Private variables ---------------------------------------------------------*/
UART_HandleTypeDef huart2;
 
/* USER CODE BEGIN PV */
 
/* USER CODE END PV */
 
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_USART2_UART_Init(void);
/* USER CODE BEGIN PFP */
 
/* USER CODE END PFP */
 
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
 
/* USER CODE END 0 */
 
/**
  * @brief  The application entry point.
  * @retval int
  */
 
 
int main(void)
{
  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();
 
  /* Configure the system clock */
  SystemClock_Config();
 
  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_USART2_UART_Init();
 
  while (1)
  {
	  HAL_UART_Receive_IT(&huart2, &recvd_data, 1); //non blocking API call
  }
 
}
 
/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
 
  /** Configure the main internal regulator output voltage 
  */
  __HAL_RCC_PWR_CLK_ENABLE();
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE3);
  /** Initializes the CPU, AHB and APB busses clocks 
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
  RCC_OscInitStruct.PLL.PLLM = 16;
  RCC_OscInitStruct.PLL.PLLN = 336;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV4;
  RCC_OscInitStruct.PLL.PLLQ = 2;
  RCC_OscInitStruct.PLL.PLLR = 2;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  /** Initializes the CPU, AHB and APB busses clocks 
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
 
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}
 
/**
  * @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;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN USART2_Init 2 */
 
  /* USER CODE END USART2_Init 2 */
 
}
 
/**
  * @brief GPIO Initialization Function
  * @param None
  * @retval None
  */
static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
 
  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOH_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();
 
  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_RESET);
 
  /*Configure GPIO pin : PC13 */
  GPIO_InitStruct.Pin = GPIO_PIN_13;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
 
  /*Configure GPIO pin : LD2_Pin */
  GPIO_InitStruct.Pin = LD2_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(LD2_GPIO_Port, &GPIO_InitStruct);
 
}
 
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
	 if(recvd_data == 'a')
	 {
		  HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_SET);
	 }
	 else
	 {
		 HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_SET);
 
	 }
}
 
void Error_Handler(void)
{
 
}
 
#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t *file, uint32_t line)
{ 
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     tex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */
 
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

As you can see I'm calling HAL_UART_Receive_IT to receive the data from Tera Term into non-blocking mode and store it into recv_data buffer. I have configured Tera Term accordingly(baud rate for the port).

I have implemented HAL_UART_RxCpltCallback in main.c and I try to light up the led there. So when a character is received the code should get into this routine and light up the LED.

However the code never reaches HAL_UART_RxCpltCallback routine :(.

I have tried sending a character from Tera Term and then stepping into HAL_UART_Receive_IT function in debug mode to see what happens. It would appear that no matter what character I type in Tera Term the value this function for pData argument is always '0/'. The way I send characters in Tera Term is simply writing them into the terminal. I guess that's the way to do it I tried also pressing enter same result. After this the function returns HAL_OK but the interrupt routine does not get fired. The next time I try to enter HAL_UART_Receive_IT function again it always returns HAL_BUSY.

Please help me understand why this does not work as expected. THank you!

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PPopo
Senior

‎2019-12-15 02:57 AM

I have identified the problem. I'm stupid and I forgot to enable USART2 global interrupt from CubeMx(USART2->NVIC settings I needed to check 'Enable global USART isr' tickbox.

View solution in original post

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waclawek.jan
Guru

‎2019-12-14 10:17 AM

> while (1)

> {

> HAL_UART_Receive_IT(&huart2, &recvd_data, 1); //non blocking API call

> }

I don't use Cube, but you are probably not supposed to call this function in a loop.

If you insist on using Cube, you may want to have a look at the examples in CubeF4, for any board (the EVAL boards tend to have more examples than other boards), UART will be the same.

JW

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Piranha
Chief II

‎2019-12-14 10:35 AM

Where is the Rx/Tx pin configuration?

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PPopo
Senior
In response to Piranha

‎2019-12-14 10:50 AM

It is in the function below which is called by HAL_UART_Init function(line 164 from my code posted above):

void HAL_UART_MspInit(UART_HandleTypeDef* huart)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  if(huart->Instance==USART2)
  {
  /* USER CODE BEGIN USART2_MspInit 0 */
 
  /* USER CODE END USART2_MspInit 0 */
    /* Peripheral clock enable */
    __HAL_RCC_USART2_CLK_ENABLE();
  
    __HAL_RCC_GPIOA_CLK_ENABLE();
    /**USART2 GPIO Configuration    
    PA2     ------> USART2_TX
    PA3     ------> USART2_RX 
    */
    GPIO_InitStruct.Pin = USART_TX_Pin|USART_RX_Pin;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_PULLUP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF7_USART2;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
 
  /* USER CODE BEGIN USART2_MspInit 1 */
 
  /* USER CODE END USART2_MspInit 1 */
  }
 
}

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PPopo
Senior
In response to waclawek.jan

‎2019-12-14 10:51 AM

it is no problem if you call it in a loop. it's just a non blocking api call. if you don't call it in a loop actually you may miss the reception.

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S.Ma
Principal

‎2019-12-14 10:51 AM

For USART, go for LL (low layer): there should be code example on Nucleo projects.

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PPopo
Senior
In response to S.Ma

‎2019-12-15 01:50 AM

hi. I did look at some examples. I have no ideea what am I doing wrong :(. It may be something from Tera Term which I'm doing correctly because the code was generated by CubeMx so it should be correct.

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PPopo
Senior

‎2019-12-15 02:57 AM

I have identified the problem. I'm stupid and I forgot to enable USART2 global interrupt from CubeMx(USART2->NVIC settings I needed to check 'Enable global USART isr' tickbox.

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