GPIO Interrupt control

Configuring interrupts from GPIO pins More...

Collaboration diagram for GPIO Interrupt control:

Functions
void	gpio_configure_trigger (uint32_t gpioport, enum gpio_trigger trigger, uint8_t gpios)
	Configure the interrupt trigger on the given GPIO pins. More...
void	gpio_enable_interrupts (uint32_t gpioport, uint8_t gpios)
	Enable interrupts on specified GPIO pins. More...
void	gpio_disable_interrupts (uint32_t gpioport, uint8_t gpios)
	Disable interrupts on specified GPIO pins. More...
static bool	gpio_is_interrupt_source (uint32_t gpioport, uint8_t srcpins)
	Determine if interrupt is generated by the given pin. More...
static void	gpio_clear_interrupt_flag (uint32_t gpioport, uint8_t gpios)
	Mark interrupt as serviced. More...

Detailed Description

Configuring interrupts from GPIO pins

GPIO pins can trigger interrupts on either edges or levels. The type of trigger can be configured with gpio_configure_int_trigger(). To have an event on the given pin generate an interrupt, its interrupt source must be unmasked. This can be achieved with gpio_enable_interrupts(). Interrupts which are no longer needed can be disabled through gpio_disable_interrupts().

In order for the interrupt to generate an IRQ and a call to the interrupt service routine, the interrupt for the GPIO port must be routed through the NVIC with nvic_enable_irq(). For this last step, the nvic.h header is needed:

#include <libopencm3/lm4f/nvic.h>

Enabling an interrupt is as simple as configuring the desired trigger, unmasking the desired interrupt, and routing the desired GPIO port's interrupt through the NVIC.

// Trigger interrupt on each rising edge
gpio_configure_trigger(GPIOF, GPIO_TRIG_EDGE_RISE, GPIO0 | GPIO4);
// Unmask the interrupt on those pins
gpio_enable_interrupts(GPIOF, GPIO0 | GPIO4);
// Enable the interrupt in the NVIC as well
nvic_enable_irq(NVIC_GPIOF_IRQ);

After interrupts are properly enabled and routed through the NVIC, when an event occurs, the appropriate IRQ flag is set by hardware, and execution jumps to the GPIO ISR. The ISR should query the IRQ flags to determine which event caused the interrupt. For this, use gpio_is_interrupt_source(), with the desired GPIO flag. After one or more interrupt sources are serviced, the IRQ flags must be cleared by the ISR. This can be done with gpio_clear_interrupt_flag().

A typical GPIO ISR may look like the following:

void gpiof_isr(void)
{
     uint8_t serviced_irqs = 0;
 
     // Process individual IRQs
     if (gpio_is_interrupt_source(GPIOF, GPIO0)) {
        process_gpio0_event();
        serviced_irq |= GPIO0;
     }
     if (gpio_is_interrupt_source(GPIOF, GPIO4)) {
        process_gpio4_event();
        serviced_irq |= GPIO4;
     }
 
     // Clear the interrupt flag for the processed IRQs
     gpio_clear_interrupt_flag(GPIOF, serviced_irqs);
}

Function Documentation

gpio_clear_interrupt_flag()

static void gpio_clear_interrupt_flag ( uint32_t  gpioport, uint8_t  gpios  )

inlinestatic

Mark interrupt as serviced.

After an interrupt is services, its flag must be cleared. If the flag is not cleared, then execution will jump back to the start of the ISR after the ISR returns.

Parameters

[in]	gpioport	GPIO block register address base GPIO register base addresses
[in]	gpios	GPIO pin identifiers. Any combination of pins may be specified by OR'ing then together.

Definition at line 369 of file gpio.h.

References GPIO_ICR.

gpio_configure_trigger()

void gpio_configure_trigger	(	uint32_t	gpioport,
		enum gpio_trigger	trigger,
		uint8_t	gpios
	)

Configure the interrupt trigger on the given GPIO pins.

Sets the Pin direction, analog/digital mode, and pull-up configuration of or a set of GPIO pins on a given GPIO port.

Parameters

[in]	gpioport	GPIO block register address base GPIO register base addresses
[in]	trigger	Trigger configuration (gpio_trigger) GPIO_TRIG_LVL_LOW – Trigger on low level GPIO_TRIG_LVL_HIGH – Trigger on high level GPIO_TRIG_EDGE_FALL – Trigger on falling edges GPIO_TRIG_EDGE_RISE – Trigger on rising edges GPIO_TRIG_EDGE_BOTH – Trigger on all edges
[in]	gpios	GPIO pin identifiers. Any combination of pins may be specified by OR'ing then together

Definition at line 527 of file gpio.c.

References GPIO_IBE, GPIO_IEV, GPIO_IS, GPIO_TRIG_EDGE_BOTH, GPIO_TRIG_EDGE_FALL, GPIO_TRIG_EDGE_RISE, GPIO_TRIG_LVL_HIGH, and GPIO_TRIG_LVL_LOW.

gpio_disable_interrupts()

void gpio_disable_interrupts	(	uint32_t	gpioport,
		uint8_t	gpios
	)

Disable interrupts on specified GPIO pins.

Disable interrupts on the specified GPIO pins

Note that the NVIC must be enabled and properly configured for the interrupt to be routed to the CPU.

Parameters

[in]	gpioport	GPIO block register address base GPIO register base addresses
[in]	gpios	GPIO pin identifiers. Pins whose interrupts to disable. Any combination of pins may be specified by OR'ing them together.

Definition at line 590 of file gpio.c.

References GPIO_IM.

gpio_enable_interrupts()

void gpio_enable_interrupts	(	uint32_t	gpioport,
		uint8_t	gpios
	)

Enable interrupts on specified GPIO pins.

Enable interrupts on the specified GPIO pins

Note that the NVIC must be enabled and properly configured for the interrupt to be routed to the CPU.

Parameters

[in]	gpioport	GPIO block register address base GPIO register base addresses
[in]	gpios	GPIO pin identifiers. Pins whose interrupts to enable. Any combination of pins may be specified by OR'ing them together.

Definition at line 572 of file gpio.c.

References GPIO_IM.

gpio_is_interrupt_source()

static bool gpio_is_interrupt_source ( uint32_t  gpioport, uint8_t  srcpins  )

inlinestatic

Determine if interrupt is generated by the given pin.

Parameters

[in]	gpioport	GPIO block register address base GPIO register base addresses
[in]	srcpins	source pin or group of pins to check.

Definition at line 353 of file gpio.h.

References GPIO_MIS.