PuTTy not receiving data from UART

pb33 · ‎2025-06-17

Hello,

I am using the STMH753ZI chip on the nucleo 144 board. I cannot figure out why my UART code will not show what I am typing in my putty terminal. Attached is my main.c. Thanks.

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2025 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "uart.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "initializer.h"
#include "string.h"

/* 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 ---------------------------------------------------------*/

COM_InitTypeDef BspCOMInit;
__IO uint32_t BspButtonState = BUTTON_RELEASED;

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(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)
{

  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_USART2_UART_Init();
  MX_USART3_UART_Init();
  /* USER CODE BEGIN 2 */

  HAL_UART_Receive_IT(&huart3, rx_data, 6);
  /* USER CODE END 2 */

  /* Initialize leds */
  BSP_LED_Init(LED_GREEN);
  BSP_LED_Init(LED_BLUE);
  BSP_LED_Init(LED_RED);

  /* Initialize USER push-button, will be used to trigger an interrupt each time it's pressed.*/
  BSP_PB_Init(BUTTON_USER, BUTTON_MODE_EXTI);

  /* Initialize COM1 port (115200, 8 bits (7-bit data + 1 stop bit), no parity */
  BspCOMInit.BaudRate   = 115200;
  BspCOMInit.WordLength = COM_WORDLENGTH_8B;
  BspCOMInit.StopBits   = COM_STOPBITS_1;
  BspCOMInit.Parity     = COM_PARITY_NONE;
  BspCOMInit.HwFlowCtl  = COM_HWCONTROL_NONE;
  if (BSP_COM_Init(COM1, &BspCOMInit) != BSP_ERROR_NONE)
  {
    Error_Handler();
  }

  /* USER CODE BEGIN BSP */

  /* -- Sample board code to send message over COM1 port ---- */
  printf("Welcome to STM32 world !\n\r");

  /* -- Sample board code to switch on leds ---- */
//  BSP_LED_On(LED_GREEN);
//  BSP_LED_On(LED_BLUE);
//  BSP_LED_On(LED_RED);

  /* USER CODE END BSP */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {

    /* -- Sample board code for User push-button in interrupt mode ---- */
//    if (BspButtonState == BUTTON_PRESSED)
//    {
//      /* Update button state */
//      BspButtonState = BUTTON_RELEASED;
//      /* -- Sample board code to toggle leds ---- */
//      BSP_LED_Toggle(LED_GREEN);
//      BSP_LED_Toggle(LED_BLUE);
//      BSP_LED_Toggle(LED_RED);
//
//      /* ..... Perform your action ..... */
//    }




    /* USER CODE END WHILE */
//	  HAL_UART_Transmit(&huart3, tx_buffer, strlen((char*)tx_buffer), 10);
//	  HAL_Delay(1000);




    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

/**
  * @brief BSP Push Button callback
  * @PAram Button Specifies the pressed button
  * @retval None
  */
void BSP_PB_Callback(Button_TypeDef Button)
{
  if (Button == BUTTON_USER)
  {
    BspButtonState = BUTTON_PRESSED;
  }
}

/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  __disable_irq();
  while (1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}

#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,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

Andrew Neil · ‎2025-06-17

@pb33 wrote:
I cannot figure out why my UART code will not show what I am typing in my putty terminal.

So what have you tried so far?

Have you put an oscilloscope probe onto the STM32 UART's RX pin to see if anything is actually reaching there?

Does your printf work ?

You're using UART3 - how is that routed to your PuTTY terminal ?

Before trying the added complexities of interrupts, have you got it working using the basic, blocking HAL_UART_Receive() ?

I can't see a callback for your UART receive?

PS:

The title says, "PuTTy not receiving data from UART"

But the post says, "UART code will not show what I am typing in my putty terminal"

So which is it?

Are you asking about PuTTY receiving from the UART, or the UART receiving from PuTTY ?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

pb33 · ‎2025-06-17

I am able to read data from the controller through PuTTy using HAL_UART_Transmit(). My printf works as well. UART3 is what is default for my printf, and originally my printf worked and my HAL_UART_Transmit() did not. So I reconfigured the HAL function to initialize through UART3 and not use UART2 at all. Below is my UART3 initializer function. The UART2 is exactly the same. Thanks.

void MX_USART3_UART_Init(void)
{

  /* USER CODE BEGIN USART3_Init 0 */

  /* USER CODE END USART3_Init 0 */

  /* USER CODE BEGIN USART3_Init 1 */

  /* USER CODE END USART3_Init 1 */
  huart3.Instance = USART3;
  huart3.Init.BaudRate = 115200;
  huart3.Init.WordLength = UART_WORDLENGTH_8B;
  huart3.Init.StopBits = UART_STOPBITS_1;
  huart3.Init.Parity = UART_PARITY_NONE;
  huart3.Init.Mode = UART_MODE_TX_RX;
  huart3.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart3.Init.OverSampling = UART_OVERSAMPLING_16;
  huart3.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart3.Init.ClockPrescaler = UART_PRESCALER_DIV1;
  huart3.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  if (HAL_UART_Init(&huart3) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_UARTEx_SetTxFifoThreshold(&huart3, UART_TXFIFO_THRESHOLD_1_8) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_UARTEx_SetRxFifoThreshold(&huart3, UART_RXFIFO_THRESHOLD_1_8) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_UARTEx_DisableFifoMode(&huart3) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN USART3_Init 2 */

  /* USER CODE END USART3_Init 2 */

}

Andrew Neil · ‎2025-06-17

You didn't answer the questions:

what have you tried so far to debug the problem?
Have you put an oscilloscope probe onto the STM32 UART's RX pin to see if anything is actually reaching there?
You're using UART3 - how is that routed to your PuTTY terminal ?
Before trying the added complexities of interrupts, have you got it working using the basic, blocking HAL_UART_Receive() ?
I can't see a callback for your UART receive?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

pb33 · ‎2025-06-17

Also, this is my uart.c file. At the bottom is my callback to my UART receive:

/*
 * uart.c
 *
 *  Created on: Jun 16, 2025
 *      Author: peterb33
 */
#include "uart.h"

UART_HandleTypeDef huart2;
UART_HandleTypeDef huart3;

//What I am telling the controller to send:
uint8_t tx_buffer[9] = "Hello\n\r";
uint8_t rx_indx = 0;
uint8_t rx_data[6];
uint8_t RX_BUF_SIZE = 100;
uint8_t rx_buffer[100];
uint8_t transfer_cplt;

/**
  * @brief USART2 Initialization Function
  * @PAram None
  * @retval None
  */
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 */

}

/**
  * @brief USART3 Initialization Function
  * @PAram None
  * @retval None
  */
void MX_USART3_UART_Init(void)
{

  /* USER CODE BEGIN USART3_Init 0 */

  /* USER CODE END USART3_Init 0 */

  /* USER CODE BEGIN USART3_Init 1 */

  /* USER CODE END USART3_Init 1 */
  huart3.Instance = USART3;
  huart3.Init.BaudRate = 115200;
  huart3.Init.WordLength = UART_WORDLENGTH_8B;
  huart3.Init.StopBits = UART_STOPBITS_1;
  huart3.Init.Parity = UART_PARITY_NONE;
  huart3.Init.Mode = UART_MODE_TX_RX;
  huart3.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart3.Init.OverSampling = UART_OVERSAMPLING_16;
  huart3.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart3.Init.ClockPrescaler = UART_PRESCALER_DIV1;
  huart3.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  if (HAL_UART_Init(&huart3) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_UARTEx_SetTxFifoThreshold(&huart3, UART_TXFIFO_THRESHOLD_1_8) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_UARTEx_SetRxFifoThreshold(&huart3, UART_RXFIFO_THRESHOLD_1_8) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_UARTEx_DisableFifoMode(&huart3) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN USART3_Init 2 */

  /* USER CODE END USART3_Init 2 */

}


/**
  * @brief  Rx Transfer completed callback.
  * @PAram  huart UART handle.
  * @retval None
  */
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
    /* Prevent unused argument(s) compilation warning */
    UNUSED(huart);
    /* NOTE: This function should not be modified, when the callback is needed,
             the HAL_UART_RxCpltCallback could be implemented in the user file
     */

    HAL_UART_Transmit(&huart3, rx_data, 6, 10);


}

Saket_Om · ‎2025-06-17

Hello @pb33

Please refer to the example below:

STM32CubeH7/Projects/STM32H735G-DK/Examples/UART/UART_Printf/Src/main.c at master · STMicroelectronics/STM32CubeH7 · GitHub

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.
Saket_Om

pb33 · ‎2025-06-17

My printf function works on UART3, and so does HAL_UART_Transmit(). My issue is that I cannot type in the terminal commands like "LED ON".

Andrew Neil · ‎2025-06-17

@pb33 wrote:
My issue is that I cannot type in the terminal commands like "LED ON".

You mean, when you type in the terminal, you don't receive the characters in your STM32 UART code ?

Note that you won't see anything on PuTTY as you type unless have have 'Local Echo' set ...

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

pb33 · ‎2025-06-17

No, sorry for not being clear. My issue is that I run my code, and can see printfs in the terminal, but when I try to also type strings in manually, nothing shows up.

Saket_Om · ‎2025-06-17

Please refer to the UART HyperTerminal example below:

STM32CubeH7/Projects/STM32H743I-EVAL/Examples/UART/UART_HyperTerminal_IT/Src/main.c at master · STMicroelectronics/STM32CubeH7 · GitHub

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.
Saket_Om