Various uses of Delay in STM32

[vishnu_illikkal]

This is to document various uses of delays like HAL_Delay() in STM32 code.

I have found 2 decent uses 

1. Put at the start of  /* USER CODE BEGIN 2 */ to stop the code from executing when we are reprogramming the board.

2. Put at the start of  /* USER CODE BEGIN 2 */ to give time to properly initialize DMA related functionality.

/* USER CODE BEGIN 2 */

HAL_Delay(2000);

HAL_UARTEx_ReceiveToIdle_DMA( &huart7,

gsm_response_buffer,

GSM_RESPONSE_BUFFER_SIZE);

__HAL_DMA_DISABLE_IT(&hdma_uart7_rx, DMA_IT_HT);

/* USER CODE END 2 */

without the delay the DMA reception was not working.

Please put any other / any modification anyone find / know here to make it as a central repository.

Edited by ST moderator to be inline with the community rules especially with the code sharing. In next time please use </> button to paste your code. Please read this post: How to insert source code

[AScha.3]

Right,

but no need to wait so long time;

i have/need it, because attached LCD/TFT etc. needs some time to be ready to work , so:

 ....
  MX_I2C1_Init();
  MX_ADC1_Init();

  /* USER CODE BEGIN 2 */

// live variables decaration maybe - must - be here !!!!
//  initialise_monitor_handles();


  HAL_Delay(50);	// wait for LCD etc. power up ********************************
....

50...100 ms usually good value here.

[Andrew Neil]

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@vishnu_illikkal wrote:

1. Put at the start of  /* USER CODE BEGIN 2 */ to stop the code from executing when we are reprogramming the board

---

That's only necessary if your code does stuff like putting the CPU to sleep, and/or reconfigures the debug pins.

And, for such purposes, it should be in USER CODE BEGIN Init - immediately after HAL_Init():

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */
                                    <<<<< Here!
  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

Even in such cases, connecting under hardware reset should gain access.

---

@vishnu_illikkal wrote:

2. Put at the start of  /* USER CODE BEGIN 2 */ to give time to properly initialize DMA related functionality.

---

Arbitrary delays are a band-aid fix at best.

If a process needs time to complete, you should wait on some specific state/event which explicitly shows that it has finished.