interrupt on BeagleBone

QNX DEVELOPERS General Programming
1

Hi guys,
I’m trying to use the interrupts on my BeagleBone running QNX 6.5.

I would use the GPIO1_12 on P8 header connector as source. My intention should be to detect when a user press a button and the GPIO1_12 falls to GND.
So, in order to do that, I set-up the GPIO1_12 as input, in pullup configuration and setup the GPIO_FALLINGDETECT register.

Unfortunately something goes wrong and when I try to press the button, nothing happens.

Here is my code:

#include <cstdlib>
#include <iostream>
#include <sys/mman.h>
#include <pthread.h>
#include <sys/neutrino.h>
#include <errno.h>
#include <stdint.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdint.h>
#include <hw/inout.h>
#include <am335x.h>
#include <stdio.h>

#define AM335X_CTRL_BASE	0x44E10000
#define conf_gpmc_ad12		0x0830 // (AM335X_CTRL_BASE+0x0830)
#define SLEWCTRL			(0x1 << 6)
#define	RXACTIVE			(0x1 << 5)
#define	PULLUP_EN			(0x1 << 4) /* Pull UP Selection */
#define PULLUDEN			(0x0 << 3) /* Pull up enabled */
#define PULLUDDIS			(0x1 << 3) /* Pull up disabled */
#define MODE(val)			val
#define GPIO_OE 			0x134
#define AM335X_GPIO_SIZE	0x00001000
#define AM335X_GPIO1_BASE   0x4804C000
#define GPIO1_IRQ 98

int init_gpio1_12(void);
const struct sigevent * isr_handler (void *arg, int id);
void * int_thread (void *arg);

struct sigevent event;
uintptr_t ptr;
uintptr_t ptr2;
int count;
int error;

int main(int argc, char *argv[]) {

	init_gpio1_12();

	event.sigev_notify = SIGEV_INTR;

	printf("Creating interrupt thread…\n");

	pthread_create (NULL, NULL, int_thread, NULL);
	delay(5);

	while(!error) {
	printf("count=%i\n", count);
	fflush(stdout);
	sleep(1);
	}

    return EXIT_SUCCESS;

}

int init_gpio1_12()
{
	int pad;

   	ThreadCtl(_NTO_TCTL_IO, 0);

   	ptr = (uintptr_t)mmap_device_memory(0, AM335X_CTRL_BASE+0x0840, PROT_READ|PROT_WRITE|PROT_NOCACHE, 0, AM335X_CTRL_BASE);

	if ( ptr == MAP_DEVICE_FAILED ) {
		perror( "mmap_device_memory for physical address failed");
		return -1;
	}

	pad = in32(ptr + conf_gpmc_ad12) & 0x0000ffff;

	out32(ptr + conf_gpmc_ad12, MODE(7) | PULLUDEN | PULLUP_EN | RXACTIVE | SLEWCTRL);

	pad = in32(ptr + conf_gpmc_ad12);

   	ptr2 = (uint32_t) mmap_device_memory(0, AM335X_GPIO_SIZE, PROT_READ|PROT_WRITE|PROT_NOCACHE, 0, AM335X_GPIO1_BASE);

	if ( ptr2 == MAP_DEVICE_FAILED ) {
		perror( "mmap_device_memory for physical address failed");
		return -1;
	}

	out32(ptr2 + GPIO_OE,(1<<12));

	out32(ptr2 + GPIO_FALLINGDETECT, (1 << 12));
}

const struct sigevent * isr_handler (void *arg, int id)
{
	return (&event);
}

void * int_thread (void *arg)
{
	// enable I/O privilege
	ThreadCtl (_NTO_TCTL_IO, 0);

	// attach the ISR to IRQ
	if (InterruptAttach (GPIO1_IRQ, isr_handler, NULL, 0, _NTO_INTR_FLAGS_TRK_MSK) == -1)
	{
		error = 1;
	}

	while (1)
	{
		InterruptWait (NULL, NULL);
		count++;
	}
}

Someone can help me? :neutral_face:

Thanks

Alessandro

2

Why not put the count++ in the ISR? That would eliminate the possibility of error in the notification.

3

Hi maschoen,
thanks for your suggestion, but unfortunaely it doesn’t work.
But if I want to detect a FALLING EDGE, I should put the interrupt in PULLUP configuration, right?

Bye

4

What doesn’t work? If you put the count++ inside the isr, either the count increases or it doesn’t and you know more.
If it increments, you have a software problem. If it doesn’t increment, the interupt isn’t firing and you know you have a hardware problem.

Well, I’m not much of a hardware guy. What you say sounds right. The interrupt controller has to be set up right to detect the falling edge.

5

Hi maschoen,
in order to avoid errors on hardware side, I’ve tried to check the interrupt with a simple test. After running the code, I’ve tried to connect the GPIO to GND in order to detect the falling edge, but it didn’t work.

Bye