TS-4700 Interrupts example code

From Technologic Systems Manuals

This example below will work with any of our products that support userspace IRQs. It opens the IRQ number specified in the first argument, and prints when it detects an IRQ.

#include <stdio.h>
#include <fcntl.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <unistd.h>

int main(int argc, char **argv)
{
	char proc_irq[32];
	int ret, irqfd = 0;
	int buf; // Holds irq junk data
	fd_set fds;

	if(argc < 2) {
		printf("Usage: %s <irq number>\n", argv[0]);
		return 1;
	}

	snprintf(proc_irq, sizeof(proc_irq), "/proc/irq/%d/irq", atoi(argv[1]));
	irqfd = open(proc_irq, O_RDONLY| O_NONBLOCK, S_IREAD);

	if(irqfd == -1) {
		printf("Could not open IRQ %s\n", argv[1]);
		return 1;
	}
	
	while(1) {
		FD_SET(irqfd, &fds); //add the fd to the set
		// See if the IRQ has any data available to read
		ret = select(irqfd + 1, &fds, NULL, NULL, NULL);
		
		if(FD_ISSET(irqfd, &fds))
		{
			FD_CLR(irqfd, &fds);  //Remove the filedes from set
			printf("IRQ detected\n");
			
			// Clear the junk data in the IRQ file
			read(irqfd, &buf, sizeof(buf));
		}
		
		//Sleep, or do any other processing here
		usleep(10000);
	}
	
	return 0;
}