GPIO set certain bits without affecting others

[chriskuku]

BTW, what is the forum to ask general programming questions on STM32 architecture?
STM32F103C8Tx
I have two timer interrupt routines, sharing the

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef* htim)

call. Depending on which handle is passed, I process the code for TIM1 or TIM3.
When I enter TIM3 code A0,A1,A2,and A3 of port GPIOA are set to all 1. I achieved this by the statement

GPIOA->ODR=0xffff on initialization and whenever I exit the ISR. On entry I set GPIOA->ODR=0xffff&(~1)
(the 1 is a rotating pattern that sets A0-A3).

Now I want to toggle A4 in the code for TIM1 without affecting bits A0-A3 and A4 shouldn't be affected during the manipulation of A0-A3 in the code for TIM3.

How can I achieve this if at all?

[KnarfB · Accepted solution]

This can be done with the Port bit set/reset register (GPIOx_BSRR). See the Reference manual (RM0008).

hth

KnarfB

[chriskuku]

Are there HAL functions for this, too?

[Piranha]

What impedes you just opening the header file and looking at those functions?

[Tesla DeLorean]

Frequently expressed as Macros, suggest you Grep the source, or Find-In-Files, save you hours

[TDK]

Yes, HAL_GPIO_WritePin/HAL_GPIO_TogglePin.

/**
  * @brief  Toggles the specified GPIO pins.
  * @PAram  GPIOx: Where x can be (A..K) to select the GPIO peripheral.
  * @PAram  GPIO_Pin: Specifies the pins to be toggled.
  * @retval None
  */
void HAL_GPIO_TogglePin(GPIO_TypeDef *GPIOx, uint16_t GPIO_Pin)
{
  uint32_t odr;

  /* Check the parameters */
  assert_param(IS_GPIO_PIN(GPIO_Pin));

  /* get current Output Data Register value */
  odr = GPIOx->ODR;

  /* Set selected pins that were at low level, and reset ones that were high */
  GPIOx->BSRR = ((odr & GPIO_Pin) << GPIO_NUMBER) | (~odr & GPIO_Pin);
}

[Piranha]

By the way the first odr & for the shifted reset bits is useless. ST was informed about this, but still implemented the bloated version.