Basic interrupt example not working due to Nios crash during startup code.

Hello Everybody,

I am trying to get a very basic interrupt demo program to work but Nios crashed during its boot code.

It very difficult to find a solution since for me this problem is system related and very difficult to debug.

The program:

#include <stdio.h># include <stdio.h># include <unistd.h># include "system.h"# include "altera_avalon_pio_regs.h"# include "sys/alt_irq.h"
volatile int n=0;
volatile int edge_capture;
extern int alt_irq_register (alt_u32 id,
                             void*   context,
                             alt_isr_func handler);
 void handle_button_interrupts(void* context, alt_u32 id)
 {
    volatile int* edge_capture_ptr = (volatile int*) context;
    *edge_capture_ptr = IORD_ALTERA_AVALON_PIO_EDGE_CAP(PIO_0_BASE);
    n++;
    IOWR_ALTERA_AVALON_PIO_EDGE_CAP(PIO_0_BASE, 0);
}
void init_pio()
{
 void* edge_capture_ptr = (void*) &edge_capture;
 IOWR_ALTERA_AVALON_PIO_IRQ_MASK(PIO_0_BASE, 0xf);
 IOWR_ALTERA_AVALON_PIO_EDGE_CAP(PIO_0_BASE, 0x0);
 alt_irq_register( PIO_0_IRQ, edge_capture_ptr,(alt_isr_func*) handle_button_interrupts );
}
int main()
{
  init_pio();
  while (1)
  {
   printf("Hello from Nios II interrupt count = %d !\n",n);
   usleep(10000000);
  }
  return 0;
}

The place where Nios crashes is (exception thrown):

void alt_io_redirect(const char* stdout_dev, 
                     const char* stdin_dev, 
                     const char* stderr_dev)
{
  /* Redirect the channels */
  alt_open_fd (&alt_fd_list, stdout_dev, O_WRONLY, 0777); // here
  alt_open_fd (&alt_fd_list, stdin_dev, O_RDONLY, 0777);
  alt_open_fd (&alt_fd_list, stderr_dev, O_WRONLY, 0777);
}  

The code is called from the NIOS startup routine that is before my main() program code is activated.

Therefore i cannot assume my code is the culprit.

JTAG_UART is connected to CPU using interrupt id 0

PIO is connected to CPU using interrupt id 1

Quartus project in attachement for those really interested

Board used: DE2-115

Question:

Any ideas regarding the culprit in this case?

I am using legacy approach to interrupt handling, could it be that there are additional things to take into account ?

Has anybody a simple working DE2 project to share?

Best Regards,

Johi.