@par Example Description
UART transmission (transmit/receive) in DMA mode between two boards.
Board: STM32F769I-DISCOVERY (embeds a STM32F769xx device)
Tx Pin: CN4.D1
Rx Pin: CN4.D0
_________________________ _________________________
| ______________| |______________ |
| |USART | | USART| |
| | | | | |
| | TX |_____________________| RX | |
| | | | | |
| | | | | |
| | | | | |
| | RX |_____________________| TX | |
| | | | | |
| |______________| |______________| |
| | | |
| GND|_____________________|GND |
|_STM32_Board 1___________| |_STM32_Board 2___________|
Two identical boards are connected as shown on the picture above.
Board 1: transmitting then receiving board
Board 2: receiving then transmitting board
The user presses the User push-button on board 1.
Then, board 1 sends in DMA mode a message to board 2 that sends it back to board 1 in DMA mode as well.
Finally, board 1 and 2 compare the received message to that sent.
If the messages are the same, the test passes.
WARNING: as both boards do not behave the same way, "TRANSMITTER_BOARD" compilation
switch is defined in /Src/main.c and must be enabled at compilation time before loading the executable in the board that first transmits then receives.
The receiving then transmitting board needs to be loaded with an executable software obtained with TRANSMITTER_BOARD disabled.
STM32F769I-DISCOVERY board LED is used to monitor the transfer status:
- While board 1 is waiting for the user to press the User push-button, its LED1 is blinking rapidly (100 ms period).
- While board 2 is waiting for the message from board 1, its LED1 is emitting
a couple of flashes every half-second.
- When the test passes, LED1 on both boards is turned on, otherwise the test has failed.
- If there is an initialization or transfer error, LED1 is slowly blinking (1 sec. period).
At the beginning of the main program the HAL_Init() function is called to reset
all the peripherals, initialize the Flash interface and the systick.
Then the SystemClock_Config() function is used to configure the system
clock (SYSCLK) to run at 216 MHz.
The UART is configured as follows:
- BaudRate = 9600 baud
- Word Length = 8 bits (8 data bits, no parity bit)
- One Stop Bit
- No parity
- Hardware flow control disabled (RTS and CTS signals)
- Reception and transmission are enabled in the time
@note USARTx/UARTx instance used and associated resources can be updated in "main.h"
file depending hardware configuration used.
@note When the parity is enabled, the computed parity is inserted at the MSB
position of the transmitted data.
@note Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds)
based on variable incremented in SysTick ISR. This implies that if HAL_Delay() is called from
a peripheral ISR process, then the SysTick interrupt must have higher priority (numerically lower)
than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
@note The application need to ensure that the SysTick time base is always set to 1 millisecond
to have correct HAL operation.
@par Keywords
Connectivity, UART, Baud rate, RS-232, Full-duplex, DMA, Parity, Stop bit, Transmission, Reception,
@Note If the user code size exceeds the DTCM-RAM size or starts from internal cacheable memories (SRAM1 and SRAM2),that is shared between several processors,
then it is highly recommended to enable the CPU cache and maintain its coherence at application level.
The address and the size of cacheable buffers (shared between CPU and other masters) must be properly updated to be aligned to cache line size (32 bytes).
@Note It is recommended to enable the cache and maintain its coherence, but depending on the use case
It is also possible to configure the MPU as "Write through", to guarantee the write access coherence.
In that case, the MPU must be configured as Cacheable/Bufferable/Not Shareable.
Even though the user must manage the cache coherence for read accesses.
Please refer to the AN4838 “Managing memory protection unit (MPU) in STM32 MCUs”
Please refer to the AN4839 “Level 1 cache on STM32F7 Series”
Code:
I compile both code of TX and RX boards in 1 main.c file.
/* Includes ------------------------------------------------------------------*/
#include "main.h"
/** @addtogroup STM32F7xx_HAL_Examples
* @{
*/
/** @addtogroup UART_TwoBoards_ComDMA
* @{
*/
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
#define TRANSMITTER_BOARD
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
/* UART handler declaration */
UART_HandleTypeDef UartHandle;
__IO ITStatus UartReady = RESET;
__IO uint32_t UserButtonStatus = 0; /* set to 1 after User Button interrupt */
/* Buffer used for transmission */
uint8_t aTxBuffer[] = " ****UART_TwoBoards communication based on DMA**** ****UART_TwoBoards communication based on DMA**** ****UART_TwoBoards communication based on DMA**** ";
/* Buffer used for reception */
uint8_t aRxBuffer[RXBUFFERSIZE];
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void Error_Handler(void);
static uint16_t Buffercmp(uint8_t* pBuffer1, uint8_t* pBuffer2, uint16_t BufferLength);
static void CPU_CACHE_Enable(void);
/* Private functions ---------------------------------------------------------*/
/**
* @brief Main program
* @param None
* @retval None
*/
int main(void)
{
/* Enable the CPU Cache */
CPU_CACHE_Enable();
/* STM32F7xx HAL library initialization:
- Configure the Flash ART accelerator
- Systick timer is configured by default as source of time base, but user
can eventually implement his proper time base source (a general purpose
timer for example or other time source), keeping in mind that Time base
duration should be kept 1ms since PPP_TIMEOUT_VALUEs are defined and
handled in milliseconds basis.
- Set NVIC Group Priority to 4
- Low Level Initialization
*/
HAL_Init();
/* Configure the system clock to 216 MHz */
SystemClock_Config();
/* Configure LED1 & LED2 */
BSP_LED_Init(LED1);
BSP_LED_Init(LED2);
/*##-1- Configure the UART peripheral ######################################*/
/* Put the USART peripheral in the Asynchronous mode (UART Mode) */
/* UART configured as follows:
- Word Length = 8 Bits
- Stop Bit = One Stop bit
- Parity = None
- BaudRate = 9600 baud
- Hardware flow control disabled (RTS and CTS signals) */
UartHandle.Instance = USARTx;
UartHandle.Init.BaudRate = 9600;
UartHandle.Init.WordLength = UART_WORDLENGTH_8B;
UartHandle.Init.StopBits = UART_STOPBITS_1;
UartHandle.Init.Parity = UART_PARITY_NONE;
UartHandle.Init.HwFlowCtl = UART_HWCONTROL_NONE;
UartHandle.Init.Mode = UART_MODE_TX_RX;
if(HAL_UART_DeInit(&UartHandle) != HAL_OK)
{
Error_Handler();
}
if(HAL_UART_Init(&UartHandle) != HAL_OK)
{
Error_Handler();
}
#ifdef TRANSMITTER_BOARD
/* Configure User push-button in Interrupt mode */
BSP_PB_Init(BUTTON_USER, BUTTON_MODE_EXTI);
/* Wait for User push-button press before starting the Communication.
In the meantime, LED1 is blinking */
while(UserButtonStatus == 0)
{
/* Toggle LED1*/
BSP_LED_Toggle(LED1);
HAL_Delay(100);
}
BSP_LED_Off(LED1);
/* The board sends the message and expects to receive it back */
/* DMA is programmed for reception before starting the transmission, in order to
be sure DMA Rx is ready when board 2 will start transmitting */
/*##-2- Program the Reception process #####################################*/
if(HAL_UART_Receive_DMA(&UartHandle, (uint8_t *)aRxBuffer, RXBUFFERSIZE) != HAL_OK)
{
Error_Handler();
}
/*##-3- Start the transmission process #####################################*/
/* While the UART in reception process, user can transmit data through
"aTxBuffer" buffer */
if(HAL_UART_Transmit_DMA(&UartHandle, (uint8_t*)aTxBuffer, TXBUFFERSIZE)!= HAL_OK)
{
Error_Handler();
}
/*##-4- Wait for the end of the transfer ###################################*/
while (UartReady != SET)
{
}
/* Reset transmission flag */
UartReady = RESET;
#else
/* The board receives the message and sends it back */
/*##-2- Put UART peripheral in reception process ###########################*/
if(HAL_UART_Receive_DMA(&UartHandle, (uint8_t *)aRxBuffer, RXBUFFERSIZE) != HAL_OK)
{
Error_Handler();
}
/*##-3- Wait for the end of the transfer ###################################*/
/* While waiting for message to come from the other board, LED1 is
blinking according to the following pattern: a double flash every half-second */
while (UartReady != SET)
{
BSP_LED_On(LED1);
HAL_Delay(100);
BSP_LED_Off(LED1);
HAL_Delay(100);
BSP_LED_On(LED1);
HAL_Delay(100);
BSP_LED_Off(LED1);
HAL_Delay(500);
}
/* Reset transmission flag */
UartReady = RESET;
BSP_LED_Off(LED1);
/*##-4- Start the transmission process #####################################*/
/* While the UART in reception process, user can transmit data through
"aTxBuffer" buffer */
if(HAL_UART_Transmit_DMA(&UartHandle, (uint8_t*)aTxBuffer, TXBUFFERSIZE)!= HAL_OK)
{
Error_Handler();
}
#endif /* TRANSMITTER_BOARD */
/*##-5- Wait for the end of the transfer ###################################*/
while (UartReady != SET)
{
}
/* Reset transmission flag */
UartReady = RESET;
/*##-6- Compare the sent and received buffers ##############################*/
if(Buffercmp((uint8_t*)aTxBuffer,(uint8_t*)aRxBuffer,RXBUFFERSIZE))
{
Error_Handler();
}
/* Turn on LED1 if test passes then enter infinite loop */
BSP_LED_On(LED2);
/* Infinite loop */
while (1)
{
}
}
/**
* @brief System Clock Configuration
* The system Clock is configured as follow :
* System Clock source = PLL (HSE)
* SYSCLK(Hz) = 216000000
* HCLK(Hz) = 216000000
* AHB Prescaler = 1
* APB1 Prescaler = 4
* APB2 Prescaler = 2
* HSE Frequency(Hz) = 25000000
* PLL_M = 25
* PLL_N = 432
* PLL_P = 2
* PLL_Q = 9
* PLL_R = 7
* VDD(V) = 3.3
* Main regulator output voltage = Scale1 mode
* Flash Latency(WS) = 7
* @param None
* @retval None
*/
void SystemClock_Config(void)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_OscInitTypeDef RCC_OscInitStruct;
HAL_StatusTypeDef ret = HAL_OK;
/* Enable HSE Oscillator and activate PLL with HSE as source */
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 = 432;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = 9;
RCC_OscInitStruct.PLL.PLLR = 7;
ret = HAL_RCC_OscConfig(&RCC_OscInitStruct);
if(ret != HAL_OK)
{
while(1) { ; }
}
/* Activate the OverDrive to reach the 216 MHz Frequency */
ret = HAL_PWREx_EnableOverDrive();
if(ret != HAL_OK)
{
while(1) { ; }
}
/* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers */
RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;
ret = HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_7);
if(ret != HAL_OK)
{
while(1) { ; }
}
}
/**
* @brief Tx Transfer completed callback
* @param UartHandle: UART handle.
* @note This example shows a simple way to report end of DMA Tx transfer, and
* you can add your own implementation.
* @retval None
*/
void HAL_UART_TxCpltCallback(UART_HandleTypeDef *UartHandle)
{
/* Set transmission flag: trasfer complete*/
UartReady = SET;
}
/**
* @brief Rx Transfer completed callback
* @param UartHandle: UART handle
* @note This example shows a simple way to report end of DMA Rx transfer, and
* you can add your own implementation.
* @retval None
*/
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *UartHandle)
{
/* Set transmission flag: trasfer complete*/
UartReady = SET;
}
/**
* @brief UART error callbacks
* @param UartHandle: UART handle
* @note This example shows a simple way to report transfer error, and you can
* add your own implementation.
* @retval None
*/
void HAL_UART_ErrorCallback(UART_HandleTypeDef *UartHandle)
{
Error_Handler();
}
/**
* @brief EXTI line detection callbacks
* @param GPIO_Pin: Specifies the pins connected EXTI line
* @retval None
*/
void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
if(GPIO_Pin == USER_BUTTON_PIN)
{
UserButtonStatus = 1;
}
}
/**
* @brief Compares two buffers.
* @param pBuffer1, pBuffer2: buffers to be compared.
* @param BufferLength: buffer's length
* @retval 0 : pBuffer1 identical to pBuffer2
* >0 : pBuffer1 differs from pBuffer2
*/
static uint16_t Buffercmp(uint8_t* pBuffer1, uint8_t* pBuffer2, uint16_t BufferLength)
{
while (BufferLength--)
{
if ((*pBuffer1) != *pBuffer2)
{
return BufferLength;
}
pBuffer1++;
pBuffer2++;
}
return 0;
}
/**
* @brief This function is executed in case of error occurrence.
* @param None
* @retval None
*/
static void Error_Handler(void)
{
/* Turn LED1 on */
BSP_LED_On(LED1);
while(1)
{
/* Error if LED1 is slowly blinking (1 sec. period) */
BSP_LED_Toggle(LED1);
HAL_Delay(1000);
}
}
#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 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) */
/* Infinite loop */
while (1)
{
}
}
#endif
/**
* @brief CPU L1-Cache enable.
* @param None
* @retval None
*/
static void CPU_CACHE_Enable(void)
{
/* Enable I-Cache */
SCB_EnableICache();
/* Enable D-Cache */
SCB_EnableDCache();
}
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