CubeF0 Low-Power Examples: Why set GPIO high speed mode?

[Andrew Neil]

In the STM32CubeF0 pack, PWR/PWR_CurrentConsumption example for Nucleo-F030R8:

void SleepMode_Measure(void)
{
  GPIO_InitTypeDef GPIO_InitStruct;

  /* Configure all GPIO as analog to reduce current consumption on non used IOs */
  /* Enable GPIOs clock */
  /* Warning : Reconfiguring all GPIO will close the connection with the debugger */
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOF_CLK_ENABLE();

  GPIO_InitStruct.Mode  = GPIO_MODE_ANALOG;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;    // <<< Here!
  GPIO_InitStruct.Pull  = GPIO_NOPULL;
  GPIO_InitStruct.Pin   = GPIO_PIN_All;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
  HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);
  HAL_GPIO_Init(GPIOF, &GPIO_InitStruct);

void StopMode_Measure(void)
{
  GPIO_InitTypeDef GPIO_InitStruct;

  /* Configure all GPIO as analog to reduce current consumption on non used IOs */
  /* Warning : Reconfiguring all GPIO will close the connection with the debugger */
  /* Enable GPIOs clock */

  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOF_CLK_ENABLE();


  GPIO_InitStruct.Mode  = GPIO_MODE_ANALOG;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;    // <<< Here!
  GPIO_InitStruct.Pull  = GPIO_NOPULL;
  GPIO_InitStruct.Pin   = GPIO_PIN_All;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
  HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);  
  HAL_GPIO_Init(GPIOF, &GPIO_InitStruct);

https://github.com/STMicroelectronics/STM32CubeF0/blob/master/Projects/STM32F030R8-Nucleo/Examples/PWR/PWR_CurrentConsumption/Src/stm32f0xx_lp_modes.c#L144

 

Why set the speed mode to High ?

The default is Low.

 

I guess it doesn’t actually make any difference, as the speed is irrelevant in Analogue mode?

So does it actually need to be explicitly set at all ?

[waclawek.jan]

Let me guess: the code was copypasted from somewhere where it did matter?

The digital output setting is irrelevant when the port is set to Analog, but the struct has to be filled in completely.

JW

[Andrew Neil]

The digital output setting is irrelevant when the port is set to Analog

I thought so.

And that should also apply to the pull-up/down:

 

[waclawek.jan]

Yes.

Basically, you could rewrite the above code as

RCC->AHBENR |= (0
  | RCC_AHBENR_IOPAEN
  | RCC_AHBENR_IOPBEN
  | RCC_AHBENR_IOPCEN
  | RCC_AHBENR_IOPDEN
  | RCC_AHBENR_IOPEEN
  | RCC_AHBENR_IOPFEN
);
GPIOA->MODER = 0xFFFFFFFF; // all pins Analog -> 0b11
GPIOB->MODER = 0xFFFFFFFF; 
GPIOC->MODER = 0xFFFFFFFF; 
GPIOD->MODER = 0xFFFFFFFF; 
GPIOE->MODER = 0xFFFFFFFF; 
GPIOF->MODER = 0xFFFFFFFF; 

(Is there any difference between those two snippets you gave above?)

JW

[Andrew Neil]

Is there any difference between those two snippets you gave above?

Not in the bits I showed - the difference in the full code is whether they subsequently go to SLEEP or STOP mode.