Nios 2 Void expression error

Troubleshooting
1

Hi,
I’m getting an invalid use of void expression error.

if(*edge_capture_ptr == 1) {
handle_interrupt(&edge_capture_ptr);
*edge_capture_ptr = 0;
}

2

That error indicates that you have a void function that returns a value. i.e.

void myFunction() {
    int myValue = 1;
    return myValue;
}

You either get rid of the return statement or declare the function with a return value like this:

int myFunction() { }

If that doesn’t resolve your issue, you will need to provide more code for a better diagnosis.

3

this is method

void handle_interrupt(int *switch_edgecaptue_value)
{
switch(switch_edgecaptue_value)
{
 case 0:
  //setting switch timer based on position set
  switch_timer =9000000;
  printf("sw_ display_hexa_value %d\n",switch_edgecaptue_value);
  break;
 case 1:
  //setting switch timer based on position set
   switch_timer = 600000;
   printf("sw_ display_hexa_value %d\n",switch_edgecaptue_value);
   break;
 case 2:
  //setting switch timer based on position set
   switch_timer = 200000;
   printf("sw_ display_hexa_value %d\n",switch_edgecaptue_value);
   break;
 case 4:
  //setting switch timer based on position set
   switch_timer = 10000;
   printf("sw_ display_hexa_value %d\n",switch_edgecaptue_value);
   break;
 case 8:
  //setting switch timer based on position set
   switch_timer = 1000;
   printf("sw_ display_hexa_value %d\n",switch_edgecaptue_value);
   break;
 case 16:
  //setting switch timer based on position set
  switch_timer = 900;
  printf("sw_ display_hexa_value %d\n",switch_edgecaptue_value);
     break;
 default:
  printf("default button is %d\n",switch_edgecaptue_value);
  switch_timer = 2500000;
  break;
}
}

void init_pio()
{
/* Recast the edge_capture pointer to match the alt_irq_register()
function* prototype. */
void* edge_capture_ptr = (void*) &edge_capture;
/* Enable first four interrupts. */
IOWR_ALTERA_AVALON_PIO_IRQ_MASK(KEY0_BASE, 0x1);
/* Reset the edge capture register. */
IOWR_ALTERA_AVALON_PIO_IRQ_MASK(SWITCH_0_BASE, 0x1F);
//start of logic
start:
display_hexa_value = 1;
for(i=0;i<16;i++)
{
 //Display display_hexa_value on Red LED
 IOWR_ALTERA_AVALON_PIO_DATA(LEDS_BASE, display_hexa_value);
 //printf("display_hexa_value is %d\t",display_hexa_value);
 //shift by 1
 display_hexa_value = display_hexa_value << 1;
 //Delay
 usleep(switch_timer);
 /* Register the interrupt handler. */
 alt_irq_register( KEY0_IRQ, edge_capture_ptr, handle_button_interrupts );
 /* Register the interrupt handler. */
 alt_irq_register( SWITCH_0_IRQ, edge_capture_ptr, handle_button_interrupts_switches );
 //checking if display_hexa_value is resetted to 1 in above registers
 
// call interrupt routine
if(*edge_capture_ptr == 1) {
handle_interrupt(*edge_capture_ptr)
*edge_capture_ptr = 0;
}
 
 if (display_hexa_value == 0x0001)
   {
    i = 0;
   }
}
for(j=0;j<16;j++)
{
 //Display display_hexa_value on Red LED
 IOWR_ALTERA_AVALON_PIO_DATA(LEDS_BASE, display_hexa_value);
 //printf("display_hexa_value is %d\t",display_hexa_value);
 //shift by 1
 display_hexa_value = display_hexa_value >> 1;
 //Delay
 usleep(switch_timer);
 /* Register the interrupt handler. */
 alt_irq_register( KEY0_IRQ, edge_capture_ptr, handle_button_interrupts );
 /* Register the interrupt handler. */
 alt_irq_register( SWITCH_0_IRQ, edge_capture_ptr, handle_button_interrupts_switches );
 //checking if display_hexa_value is resetted to 1 in above registers

// call interrupt routine
if(*edge_capture_ptr == 1) {
handle_interrupt(*edge_capture_ptr); 
*edge_capture_ptr = 0;
}
 
 if (display_hexa_value == 0x0001)
 {
  goto start;
 }
}
/*
for(i=0;i<32;i++)
{
 if(i<16)
 {
  IOWR_ALTERA_AVALON_PIO_DATA(LEDR_BASE, display_hexa_value);
  //printf("display_hexa_value is %d\n",display_hexa_value);
  display_hexa_value = display_hexa_value << 1;
  usleep(switch_timer);
  alt_irq_register( KEY_IRQ, edge_capture_ptr, handle_button_interrupts );
  alt_irq_register( SWITCHES_IRQ, edge_capture_ptr, handle_button_interrupts_switches );
  if(display_hexa_value == 1)
  {
   i=0;
  }
 }
 if(i>=16 && i<32)
 {
  IOWR_ALTERA_AVALON_PIO_DATA(LEDR_BASE, display_hexa_value);
  //printf("display_hexa_value is %d\n",display_hexa_value);
  display_hexa_value = display_hexa_value >> 1;
  usleep(switch_timer);
  alt_irq_register( KEY_IRQ, edge_capture_ptr, handle_button_interrupts );
  alt_irq_register( SWITCHES_IRQ, edge_capture_ptr, handle_button_interrupts_switches );
  if(display_hexa_value == 1)
  {
   i=0;
  }
 }
 display_hexa_value = 1;
}
*/
//display_hexa_value = 1;
}
4

Im Facing an issues in

/ call interrupt routine
if(*edge_capture_ptr == 1) {
handle_interrupt(*edge_capture_ptr)
*edge_capture_ptr = 0;
}
5

That’s because you’ve declared edge_capture_ptr as void *.

void* edge_capture_ptr = (void*) &edge_capture;

You can’t test or set a void * because the compiler has no idea of the size of the data you want to test or set. In order to use *edge_capture_ptr in an if test or as the left side of a assignment operation, you need to specify a non-zero size. For example:

uint8_t* edge_capture_ptr = (uint8_t*) &edge_capture;

That’s just an example, you need to set it to the size that it actually is, not arbitrarily one 8-bit byte, of course.

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