Dear Albrecht,

Thank you for this quick answers. I modified my C program as suggested, HOWEVER, QNX is crashing and then restart when I
 push the button to invoke interrupt during my program running. Crashing message as below and follows my modified C 
codes. Please help to take a look. Thanks in advance.

# 
Shutdown[0,0] S/C/F=0/0/0 C/D=fe01f694/fe09d02c state(1)= 1
QNX Version 6.5.0 Release 2012/06/20-13:48:57EDT
[0]PID-TID=77846-1? P/T FL=00001800/81000000 "tmp/zzzblogspot_gmichael151920897210236"
armle context[effe8ee4]:
0000: 00000001 effe8f38 00000002 00000000 00000000 effe8f48 fe09b8a8 00002000
0020: effeaff0 effeaff0 fe09d054 effe8fc4 0000000b 000ffec8 00100c58 01037d28
0040: 80000113
instruction[01037d28]:
10 80 bd e8 10 40 bd e8 85 70 ff ea 10 40 2d e9 08 40 9d e5 0b c0 a0 e3 00 00 
stack[000ffec8]:
0000: 00100d64 00689af0 00000000 000ffefc 00000004 00100664 000fff04 00000001
0020: 28000000 0000000b 00000001 00000001 000fff65 00100778 00000001 000fff65
0040: 00000000 000fff89 00000000 00000003 00100034 00000004 00000020 00000005
0060: 00000006 00000009 001006b8 00000006 00001000 00000007 01000000 0000002d
U-Boot SPL 2013.04-rc1-14237-g90639fe-dirty (Apr 13 2013 - 13:57:11)
musb-hdrc: ConfigData=0xde (UTMI-8, dyn FIFOs, HB-ISO Rx, HB-ISO Tx, SoftConn)
musb-hdrc: MHDRC RTL version 2.0 
musb-hdrc: setup fifo_mode 4
musb-hdrc: 28/31 max ep, 16384/16384 memory
..........
.......... 

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <sys/neutrino.h>
#include <unistd.h>
#include <sys/mman.h>
#include <arm/inout.h>
#include <errno.h>
#include <arm/am335x.h>
#include <sys/iofunc.h>
#include <sys/dispatch.h>

#define MY_PIN			(1<<28)
int irq  = 828;
static uint32_t irqcount = 0;


static void Delay1(volatile unsigned int count)
{
    while(count--);
}

static const struct sigevent *handler(void *area, int id)
{
	irqcount++;
	printf("enter interrupt\n");
	return NULL;
}


int main(int argc, char *argv[])
{
	if (ThreadCtl(_NTO_TCTL_IO, 0) == -1) {
		printf("ThreadCtl\r\n");
		return (!EOK);
	}

	// pin configuration ...
	uintptr_t gpio_base = mmap_device_io(AM335X_GPIO_SIZE, AM335X_GPIO1_BASE);
        if(gpio_base == MAP_DEVICE_FAILED)
        {
              perror("Can't map device I/O");
              return 0;
        }

	// set INPUT direction for MY_PIN	// 1 input
	out32( gpio_base + GPIO_OE, in32(gpio_base + GPIO_OE) | MY_PIN );

	// set Interrupt CONFIGURATION "Rising Edge/Falling Edge" for MY_PIN
	out32( gpio_base + GPIO_RISINGDETECT,  in32(gpio_base + GPIO_RISINGDETECT)  | MY_PIN );
	out32( gpio_base + GPIO_FALLINGDETECT, in32(gpio_base + GPIO_FALLINGDETECT) | MY_PIN );
	out32( gpio_base + GPIO_LEVELDETECT0,  in32(gpio_base + GPIO_LEVELDETECT0)  & ~MY_PIN );
	out32( gpio_base + GPIO_LEVELDETECT1,  in32(gpio_base + GPIO_LEVELDETECT1)  & ~MY_PIN );

	// set Interrupt ENABLED for MY_PIN
	out32( gpio_base + GPIO_IRQSTATUS_SET_0, in32(gpio_base + GPIO_IRQSTATUS_SET_0) | MY_PIN );//0x34
//	out32( gpio_base + GPIO_IRQSTATUS_SET_1, in32(gpio_base + GPIO_IRQSTATUS_SET_1) | MY_PIN );//0x3c

	// GPIO_IRQWAKEN
	out32( gpio_base + 0x44, in32(gpio_base + 0x44) | MY_PIN );
//	out32( gpio_base + 0x48, in32(gpio_base + 0x48) | MY_PIN );

	InterruptEnable();

	int result = InterruptAttach( irq, handler, &gpio_base, AM335X_GPIO_SIZE, _NTO_INTR_FLAGS_PROCESS);
	if(result == -1)
	{
		printf("InterruptAttach wrong\r\n");
	}
	else
	{
		printf("Attached IRQ ID = %d\r\n", result);
	}

	while(1)
	{
        Delay1(0xFFFFFF);
        Delay1(0xFFFFFF);
        Delay1(0xFFFFFF);
        Delay1(0xFFFFFF);

        if(in32(gpio_base + GPIO_DATAIN) & MY_PIN)
        	printf("connected %u\n", irqcount);
        else
        	printf("Disconnected %u\n", irqcount);
	}

	return EXIT_SUCCESS;
}