STM32F7 usart DMA tx

Hello ;

I am trying to test usart DMA on F7 . I only can transmite one time ; when i call usart init again its ok . but i still could not understand why .

Could you help please

 while (1)
 {
 /* USER CODE END WHILE */
 
 /* USER CODE BEGIN 3 */
		
		
 
		
		HAL_Delay(500);
		/* Get the CR register value */
 
HAL_UART_Transmit_DMA(&huart6, text, 21);
 
 
 /* USART6 DMA Init */
 /* USART6_TX Init */
 
		 
		//HAL_UART_Transmit_DMA(&huart6, text, 21);
 }
 /* USER CODE END 3 */
}

Thank you

[Tesla DeLorean]

Check for completion, check for error/status returned by function.

If processor stuck, break in with debugger and determine where. Is it expecting interrupt and callback functions to be implemented?