Interrupt on my radar application - what have I been programming ?

[Altera_Forum]

Dear Forum users, 

 I implemented with verilog a simple 32 bit wide COUNTER. Then I read the counter out with Nios and I implemented on my radar application two switches - one switch for starting the  radar pulse and one switch for displaying the result on the RS232. Now the code it functions but I do not know what I have been implementing with version 9.1.   The code will look as follows:  //PAVLE DUKANOVIC //www.dukelanovic.com //Neckarrems,19.10.2014 //  //RS232 COMMUNICATIONS //  # include<stdio.h># include<string.h># include "altera_avalon_pio_regs.h" # include "alt_types.h"# include "unistd.h" # include "system.h"# include "sys/alt_irq.h"    # define seg *(volatile unsigned char *) SEG_BASE # define bit *(volatile unsigned char *) BIT_BASE # define RESET *(volatile unsigned char *) RESET_BASE# define TRIG *(volatile unsigned char *) TRIG_BASE# define COUNTER *(volatile alt_u32 *) COUNTER_BASE# define START *(volatile alt_u32 *) START_BASE const alt_u8 duan[10]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};  // 0 1 2 3 4 5 6 7 8 9 alt_u8 num[8] = {0,0,0,0,0,0,0,0}; alt_u8 number[8]; alt_u32 n = 0;   alt_u8 key_flag; alt_u8 key_flag1;   volatile int edge_capture;   void key_ISR(void* context, alt_u32 id) {   IOWR_ALTERA_AVALON_PIO_EDGE_CAP(START_BASE,0);  IORD_ALTERA_AVALON_PIO_EDGE_CAP(START_BASE);  key_flag = 1;  }   void key3_ISR(void* context, alt_u32 id) {   IOWR_ALTERA_AVALON_PIO_EDGE_CAP(K3_BASE,0);  IORD_ALTERA_AVALON_PIO_EDGE_CAP(K3_BASE);  key_flag1 = 1;   }         void key_Init() { IOWR_ALTERA_AVALON_PIO_IRQ_MASK(START_BASE,0xF); IOWR_ALTERA_AVALON_PIO_EDGE_CAP(START_BASE,0x0); alt_irq_register(START_IRQ,NULL,key_ISR); //START_IRQ 3 }   void key3_Init() { IOWR_ALTERA_AVALON_PIO_IRQ_MASK(K3_BASE,0xF); IOWR_ALTERA_AVALON_PIO_EDGE_CAP(K3_BASE,0x0); alt_irq_register(K3_IRQ,NULL,key3_ISR); //START_IRQ 3 }   // This function will display 8 Numbers  void display(alt_u32 i) {    alt_u8 j;  num[0] = ((((((i % 10000000)%1000000)%100000)%10000)%1000)%100)%10;  num[1] = ((((((i % 10000000)%1000000)%100000)%10000)%1000)%100)/10;   num[2] = (((((i % 10000000)%1000000)%100000)%10000)%1000)/100;   num[3] = ((((i % 10000000)%1000000)%100000)%10000)/1000;   num[4] = (((i % 10000000)%1000000)%100000)/10000;   num[5] = ((i % 10000000)%1000000)/100000;   num[6] = (i % 10000000)/1000000;   num[7] = i / 10000000;     for(j=0; j<8; j++)  {  bit = ~(0x01 << j);   seg = duan[num[j]]; // here the display is switched on   usleep(100);   }    number[7] = ((((((i % 10000000)%1000000)%100000)%10000)%1000)%100)%10+0x30;  number[6] = ((((((i % 10000000)%1000000)%100000)%10000)%1000)%100)/10+0x30;   number[5] = (((((i % 10000000)%1000000)%100000)%10000)%1000)/100+0x30;   number[4] = ((((i % 10000000)%1000000)%100000)%10000)/1000+0x30;   number[3] = (((i % 10000000)%1000000)%100000)/10000+0x30;   number[2] = ((i % 10000000)%1000000)/100000+0x30;   number[1] = (i % 10000000)/1000000+0x30;   number[0] = i / 10000000+0x30;     }   int main () {    char* msg = "M01 ";  FILE* fp;      key_Init();  key3_Init();  printf("RS232 DEMO : \n");  fp = fopen (UART_NAME, "r+"); // here we initialize the RS232 port  RESET = 1;    TRIG =1;  while(1){    n = COUNTER;  display(n);  usleep(100);    if(key_flag){    TRIG = 0;  usleep(10);  fwrite (msg, strlen (msg), 1, fp); // here we write on the RS232  usleep(40000);    key_flag = 0;  TRIG = 1;    }    if(key_flag1){  fwrite (number, strlen (number), 1, fp); // here we write on the RS232  key_flag1 = 0;  }    }   return 0; }    Can you tell me where I can find a good reference about programming and handling interrupts?  What have I been doing with the initialisation of my interrupt?  void key_Init() { IOWR_ALTERA_AVALON_PIO_IRQ_MASK(START_BASE,0xF); IOWR_ALTERA_AVALON_PIO_EDGE_CAP(START_BASE,0x0); alt_irq_register(START_IRQ,NULL,key_ISR); //START_IRQ 3 }  What do those commands mean ?  Please help me.

[Altera_Forum]

https://www.altera.com/en_us/pdfs/literature/hb/nios2/n2sw_nii52010.pdf 

 https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/hb/nios2/n2sw_nii5v2.pdf  These might help.

[Altera_Forum]

This document has a C code explaining it. The content is present on pg 8-15. 

 https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/hb/nios2/n2sw_nii5v2.pdf  I hope you enabled interrupts while creating your system in qsys and did give the right priority to the different components.