Posted on January 21, 2018 at 14:23Look at the example in the appendix, or in L0Snippets:
/**
* Brief This function enables the peripheral clocks on GPIO port A,
* configures the EXTI register and NVIC IRQ.
* PA0 is set in input,no pull-up, no pull-down
* SYSCFG_EXTICR1 is kept at its reset value to select Port A for EXTI0
* Param None
* Retval None
*/
__INLINE void ConfigureExtendedIT(void)
{
/* (1) Enable the peripheral clock of GPIOA */
/* (2) Select input mode (00) on GPIOA pin 0 */
/* (3) Select Port A for pin 0 extended interrupt by writing 0000
in EXTI0 (reset value)*/
/* (4) Configure the corresponding mask bit in the EXTI_IMR register */
/* (5) Configure the Trigger Selection bits of the Interrupt line
on rising edge*/
/* (6) Configure the Trigger Selection bits of the Interrupt line
on falling edge*/
RCC->IOPENR |= RCC_IOPENR_GPIOAEN; /* (1) */
GPIOA->MODER = (GPIOA->MODER & ~(GPIO_MODER_MODE0)); /* (2) */
//SYSCFG->EXTICR[0] &= (uint16_t)~SYSCFG_EXTICR1_EXTI0_PA; /* (3) */
EXTI->IMR |= 0x0001; /* (4) */
EXTI->RTSR |= 0x0001; /* (5) */
//EXTI->FTSR |= 0x0001; /* (6) */
/* Configure NVIC for Extended Interrupt */
/* (6) Enable Interrupt on EXTI0_1 */
/* (7) Set priority for EXTI0_1 */
NVIC_EnableIRQ(EXTI0_1_IRQn); /* (6) */
NVIC_SetPriority(EXTI0_1_IRQn,0); /* (7) */
}
There's an flaw in this example as it does not enable SYSCFG by setting RCC_APB2ENR.SYSCFGEN - the example will work as it leaves the selector in SYSCFG at its reset value, but any other pin than PAx would need to have this changed.
JW
