UART RTS/CTS not working

[Ephraimoved]

Dear Sir.

I am trying to test for rts/cts , I use a program that transmit a 16 byte data

every 1 ms .

Tying rts or cts to gnd or 3.3v  makes no impact on the TX output.

How do I insure that the code  works with RTS\CTS ?

Pleas advise

[Danish1]

Hep us to help you. Show us what you've done so far:

• What board you're using, which pins you expect for TXD, RXD, CTS, RTS
• Your source code, including how you enable the handshaking.

With that, we might be able to give you pointers as to what you might have done wrong.

[Ephraimoved]

Hi

Thanks for the speedy answer .

I use  stm32u575 , uart 4, PA0 TX, PA1 RX , PA15 RTS , PB7 CTS

See attached project

Thanks

[Danish1]

Please post the source code in text form in a reply.

And images of schematics where appropriate.

An entire project is way too big for us to wade through and might contain malware so many people won't bother to look.

[Ephraimoved]

Hi 

Attached some code inn text and c files,

Thanks

Main

/* USER CODE BEGIN Header */

/**

  ******************************************************************************

  * @file           : main.c

  * @brief          : Main program body

  ******************************************************************************

  * @attention

  *

  * Copyright (c) 2024 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 "icache.h"

#include "memorymap.h"

#include "usart.h"

#include "gpio.h"

extern UART_HandleTypeDef huart4;

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

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/

void SystemClock_Config(void);

uint8_t message[16] = "Ephraim Oved  \r\n";

/* 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_MEMORYMAP_Init();

  MX_UART4_Init();

  MX_ICACHE_Init();

  /* USER CODE BEGIN 2 */

  /* USER CODE END 2 */

  /* Infinite loop */

  /* USER CODE BEGIN WHILE */

  while (1)

  {

    /* USER CODE END WHILE */

  HAL_UART_Transmit(&huart4,&message[0],16, 100);

  HAL_Delay(1);

    /* USER CODE BEGIN 3 */

  }

  /* USER CODE END 3 */

}

/**

  * @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

  */

  if (HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE4) != HAL_OK)

  {

    Error_Handler();

  }

  /** Initializes the CPU, AHB and APB buses clocks

  */

  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;

  RCC_OscInitStruct.MSIState = RCC_MSI_ON;

  RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;

  RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_4;

  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;

  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)

  {

    Error_Handler();

  }

  /** Initializes the CPU, AHB and APB buses clocks

  */

  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK

                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2

                              |RCC_CLOCKTYPE_PCLK3;

  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;

  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;

  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;

  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  RCC_ClkInitStruct.APB3CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)

  {

    Error_Handler();

  }

}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**

  * @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 */

usart.c

/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file usart.c
* @brief This file provides code for the configuration
* of the USART instances.
******************************************************************************
* @attention
*
* Copyright (c) 2024 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 "usart.h"

/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

UART_HandleTypeDef huart4;

/* UART4 init function */
void MX_UART4_Init(void)
{

/* USER CODE BEGIN UART4_Init 0 */

/* USER CODE END UART4_Init 0 */

/* USER CODE BEGIN UART4_Init 1 */

/* USER CODE END UART4_Init 1 */
huart4.Instance = UART4;
huart4.Init.BaudRate = 115200;
huart4.Init.WordLength = UART_WORDLENGTH_8B;
huart4.Init.StopBits = UART_STOPBITS_2;
huart4.Init.Parity = UART_PARITY_NONE;
huart4.Init.Mode = UART_MODE_TX_RX;
huart4.Init.HwFlowCtl = UART_HWCONTROL_RTS_CTS;
huart4.Init.OverSampling = UART_OVERSAMPLING_16;
huart4.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
huart4.Init.ClockPrescaler = UART_PRESCALER_DIV1;
huart4.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
if (HAL_UART_Init(&huart4) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_SetTxFifoThreshold(&huart4, UART_TXFIFO_THRESHOLD_1_8) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_SetRxFifoThreshold(&huart4, UART_RXFIFO_THRESHOLD_1_8) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_DisableFifoMode(&huart4) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN UART4_Init 2 */

/* USER CODE END UART4_Init 2 */

}

void HAL_UART_MspInit(UART_HandleTypeDef* uartHandle)
{

GPIO_InitTypeDef GPIO_InitStruct = {0};
RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};
if(uartHandle->Instance==UART4)
{
/* USER CODE BEGIN UART4_MspInit 0 */

/* USER CODE END UART4_MspInit 0 */

/** Initializes the peripherals clock
*/
PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_UART4;
PeriphClkInit.Uart4ClockSelection = RCC_UART4CLKSOURCE_PCLK1;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
{
Error_Handler();
}

/* UART4 clock enable */
__HAL_RCC_UART4_CLK_ENABLE();

__HAL_RCC_GPIOA_CLK_ENABLE();
__HAL_RCC_GPIOB_CLK_ENABLE();
/**UART4 GPIO Configuration
PA0 ------> UART4_TX
PA1 ------> UART4_RX
PA15 (JTDI) ------> UART4_RTS
PB7 ------> UART4_CTS
*/
GPIO_InitStruct.Pin = GPIO_PIN_0|GPIO_PIN_1|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_AF8_UART4;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

GPIO_InitStruct.Pin = GPIO_PIN_7;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
GPIO_InitStruct.Alternate = GPIO_AF8_UART4;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

/* USER CODE BEGIN UART4_MspInit 1 */

/* USER CODE END UART4_MspInit 1 */
}
}

void HAL_UART_MspDeInit(UART_HandleTypeDef* uartHandle)
{

if(uartHandle->Instance==UART4)
{
/* USER CODE BEGIN UART4_MspDeInit 0 */

/* USER CODE END UART4_MspDeInit 0 */
/* Peripheral clock disable */
__HAL_RCC_UART4_CLK_DISABLE();

/**UART4 GPIO Configuration
PA0 ------> UART4_TX
PA1 ------> UART4_RX
PA15 (JTDI) ------> UART4_RTS
PB7 ------> UART4_CTS
*/
HAL_GPIO_DeInit(GPIOA, GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_15);

HAL_GPIO_DeInit(GPIOB, GPIO_PIN_7);

/* USER CODE BEGIN UART4_MspDeInit 1 */

/* USER CODE END UART4_MspDeInit 1 */
}
}

/* USER CODE BEGIN 1 */

/* USER CODE END 1 */

[Danish1 · Accepted solution]

That looks credible to me. (Disclaimer: I don't use HAL).

So my next thoughts are that it could be one of:

• A bug in HAL and (e.g.) ST didn't correctly code that UART4 supports hardware handshaking. So it ignored your request of UART_HWCONTROL_RTS_CTS. Can you check that U(S)ART4->CR3 has the appropriate bit(s) set after HAL_UART_Init(). (If in doubt check the Reference Manual).
• A problem with your test board, perhaps GPIOB7 isn't soldered or doesn't go to where you expect on your test board. Can you program that pin to be output and see that it goes high / low when you want. Also program it to be input and verify that you can read the logic level.
• A problem with the stm32U575, and CTS isn't correctly routed to GPIOB7. I don't see mention of it in the errata, but if the chip is sufficiently new then maybe you're the first to hit this problem. Can you read the (inverted) state of CTS in U(S)ART4->ISR?