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Corrupted terminal output using USART2 on STM32F4 Discovery

Sherif Armanyous
Associate II
Posted on January 16, 2018 at 13:03

Hi ,

I am generating usart2 in STM43F407 Discovery using stmcubemx and keil where it does not work and the configuration in stmcube is as follows : > rcc - crystal oscillator - HSEPLL Source > USART2 - asynchronous -9600baud- 8bit data

Data should be 'Hello World\n' it appears on the terminal corrupted data

/* Includes ------------------------------------------------------------------*/

#include 'main.h'

#include 'stm32f4xx_hal.h'

#include <string.h>

UART_HandleTypeDef huart2;

char test[]='Hello World\n';

void SystemClock_Config(void);

static void MX_GPIO_Init(void);

static void MX_USART2_UART_Init(void);

int main(void)

{

HAL_Init();

SystemClock_Config();

MX_GPIO_Init();

MX_USART2_UART_Init();

while (1)

{

HAL_UART_Transmit(&huart2,(uint8_t *)test,strlen(test),100);

HAL_Delay(1000);

}

}

void SystemClock_Config(void)

{

RCC_OscInitTypeDef RCC_OscInitStruct;

RCC_ClkInitTypeDef RCC_ClkInitStruct;

/**Configure the main internal regulator output voltage

*/

__HAL_RCC_PWR_CLK_ENABLE();

__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

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

*/

RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;

RCC_OscInitStruct.HSEState = RCC_HSE_ON;

RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;

RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;

RCC_OscInitStruct.PLL.PLLM = 25;

RCC_OscInitStruct.PLL.PLLN = 168;

RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;

RCC_OscInitStruct.PLL.PLLQ = 4;

if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)

{

_Error_Handler(__FILE__, __LINE__);

}

/**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(__FILE__, __LINE__);

}

/**Configure the Systick interrupt time

*/

HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);

/**Configure the Systick

*/

HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);

/* SysTick_IRQn interrupt configuration */

HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);

}

/* USART2 init function */

static void MX_USART2_UART_Init(void)

{

huart2.Instance = USART2;

huart2.Init.BaudRate = 9600;

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(__FILE__, __LINE__);

}

}

/** Configure pins as

* Analog

* Input

* Output

* EVENT_OUT

* EXTI

*/

static void MX_GPIO_Init(void)

{

/* GPIO Ports Clock Enable */

__HAL_RCC_GPIOH_CLK_ENABLE();

__HAL_RCC_GPIOA_CLK_ENABLE();

}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**

* @brief This function is executed in case of error occurrence.

* @param None

* @retval None

*/

void _Error_Handler(char * file, int line)

{

/* USER CODE BEGIN Error_Handler_Debug */

/* User can add his own implementation to report the HAL error return state */

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

/**

* @}

*/

/**

* @}

*/

Note: this post was migrated and contained many threaded conversations, some content may be missing.
23 REPLIES 23
Posted on January 16, 2018 at 18:10

Thank you for letting me the root cause - it gives me whole picture. The HSI by itself has 1% of max error when in 25C - it should be enough to get UART working, I guess.

Posted on January 16, 2018 at 18:10

Thanks Mr

Neil.Andrew

for your help as it was my mistake and once I changed the HSE to 8MHZ it worked and I am happy regarding our conversation due to the knowledge I got

Posted on January 16, 2018 at 20:23

Yes, we can use HSI (highh speed internal clock)  to generate uart with low error. 

But based on STM32 Reference Manual,  HSI Should be used only if there HSE Failure. 

HSI as backup for HSE 

Posted on January 16, 2018 at 20:37

Yes, Clock Security.