I am using a stm32f103 and I'm trying to simply transmit all data received on 1 uart to another uart and vice versa.
When using 2 terminal programs it works great, everything I type gets transmitted without any issues. But if send a long string, for example '12345678' at one time, then the result is '1357'. So it's pretty much skipping every 2nd character. It feels like it misses every 2nd character when it's busy transmitting the first character.
Any ideas on how this can be changed to not do this?
This is my current code (base generated from stm32cubemx):
/* Includes ------------------------------------------------------------------*/
#include "stm32f1xx_hal.h"
/* Private variables ---------------------------------------------------------*/
UART_HandleTypeDef huart1;
UART_HandleTypeDef huart2;
DMA_HandleTypeDef hdma_usart1_rx;
DMA_HandleTypeDef hdma_usart1_tx;
DMA_HandleTypeDef hdma_usart2_rx;
DMA_HandleTypeDef hdma_usart2_tx;
/* Private variables ---------------------------------------------------------*/
uint8_t rxBuffer = '\000';
uint8_t rxBuffer2 = '\000';
uint8_t txBuffer = '\000';
uint8_t txBuffer2 = '\000';
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_DMA_Init(void);
static void MX_USART2_UART_Init(void);
static void MX_USART1_UART_Init(void);
void uart1( char *msg )
{
HAL_UART_Transmit_DMA(&huart1, (uint8_t *)msg, 1);
}
void uart2( char *msg )
{
HAL_UART_Transmit_DMA(&huart2, (uint8_t *)msg, 1);
}
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
if ( huart == &huart1 )
{
__HAL_UART_FLUSH_DRREGISTER(&huart1); // Clear the buffer to prevent overrun
txBuffer = rxBuffer;
uart2(&txBuffer);
HAL_UART_Receive_DMA(&huart1, &rxBuffer, 1);
return;
}
if ( huart == &huart2 )
{
__HAL_UART_FLUSH_DRREGISTER(&huart2); // Clear the buffer to prevent overrun
txBuffer2 = rxBuffer2;
uart1(&txBuffer2);
HAL_UART_Receive_DMA(&huart2, &rxBuffer2, 1);
return;
}
}
/* USER CODE END 0 */
int main(void)
{
/* MCU Configuration----------------------------------------------------------*/
/* 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_DMA_Init();
MX_USART2_UART_Init();
MX_USART1_UART_Init();
// starting bridge
__HAL_UART_FLUSH_DRREGISTER(&huart1);
HAL_UART_Receive_DMA(&huart1, &rxBuffer, 1);
__HAL_UART_FLUSH_DRREGISTER(&huart2);
HAL_UART_Receive_DMA(&huart2, &rxBuffer2, 1);
/* Infinite loop */
while (1)
{
}
}
/** System Clock Configuration
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct;
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSICalibrationValue = 16;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI_DIV2;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL12;
HAL_RCC_OscConfig(&RCC_OscInitStruct);
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;
HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1);
HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
/* SysTick_IRQn interrupt configuration */
HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}
/* USART1 init function */
void MX_USART1_UART_Init(void)
{
huart1.Instance = USART1;
huart1.Init.BaudRate = 230400;
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;
HAL_UART_Init(&huart1);
}
/* USART2 init function */
void MX_USART2_UART_Init(void)
{
huart2.Instance = USART2;
huart2.Init.BaudRate = 230400;
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;
HAL_UART_Init(&huart2);
}
/**
* Enable DMA controller clock
*/
void MX_DMA_Init(void)
{
/* DMA controller clock enable */
__HAL_RCC_DMA1_CLK_ENABLE();
/* DMA interrupt init */
HAL_NVIC_SetPriority(DMA1_Channel4_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(DMA1_Channel4_IRQn);
HAL_NVIC_SetPriority(DMA1_Channel5_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(DMA1_Channel5_IRQn);
HAL_NVIC_SetPriority(DMA1_Channel6_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(DMA1_Channel6_IRQn);
HAL_NVIC_SetPriority(DMA1_Channel7_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(DMA1_Channel7_IRQn);
}
/** Configure pins as
* Analog
* Input
* Output
* EVENT_OUT
* EXTI
*/
void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct;
/* GPIO Ports Clock Enable */
__GPIOA_CLK_ENABLE();
__GPIOB_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(DUT_RESET_GPIO_Port, DUT_RESET_Pin, GPIO_PIN_RESET);
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOA, LED_Pin|GPIO_PIN_15, GPIO_PIN_RESET);
/*Configure GPIO pin : DUT_RESET_Pin */
GPIO_InitStruct.Pin = DUT_RESET_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Speed = GPIO_SPEED_LOW;
HAL_GPIO_Init(DUT_RESET_GPIO_Port, &GPIO_InitStruct);
/*Configure GPIO pins : LED_Pin PA15 */
GPIO_InitStruct.Pin = LED_Pin|GPIO_PIN_15;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Speed = GPIO_SPEED_LOW;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
/*Configure GPIO pin : PB9 */
GPIO_InitStruct.Pin = GPIO_PIN_9;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
}
/* USER CODE BEGIN 4 */
/* USER CODE END 4 */
#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
/**
* @}
*/
/**
* @}
*/
Best Answer
Consider the following snippet from the STM32F1 manual regarding the USART data register and its corresponding status bit 'TXE':
Can you imagine a scenario where you are writing into the data register before the previous byte has made it into the shift register? Think about the sequence of events when you receive a stream of bytes, especially when you receive the third or fourth byte, what is your transmitter doing at this point? Is its data register occupied?
As a previous comment mentioned, you likely need a way to buffer previous byte(s) if the TXE status bit is not set. Writing into the USART data register while the TXE status bit is not set is a guaranteed way to lose information.
Edit in response to comment:
That's one way to do it, I would imagine it would work. However, I think doing away with DMA and using the USART interrupts would be a better approach. You can have 2 interrupt service routines for when a byte is received and when the transmit data register is empty. Based on those two events, you can decide to buffer the data (in the RX handler) and to empty the buffer (in TX complete handler). Care must be taken in deciding when to enable/disable the TX complete interrupt. I think the overhead of setting up DMA makes more sense for larger sequential transactions into (or out of) buffers, and less so for the single byte-by-byte case.