/*
 * nios_interrupts_updown.c
 *
 *  Created on: Oct 17, 2018
 *      Author: johnsontimoj
 */
/////////////////////////////////////
//
// Program to demonstrate interrupts
//
// this version does make use of the passed context
//
// inputs: sw0, sw1 - rising edges create interrupts
//					- incrementing/decrementing a count
//
//////////////////////////////////////
#include "system.h"					// nios
#include "altera_avalon_pio_regs.h"	//
#include "sys/alt_irq.h"			//
#include "alt_types.h"				// alt_u8
#include <stdio.h>
#include <unistd.h>					// usleep

// ISR Prototype
void io_switch_isr(void * context);
// Switch setup prototype
void io_switch_setup();

// Global variable to hold the value of the
// edge capture (context)
volatile int edge_val = 0;

int main(void){
	printf("Entered main of nios_interrupts_updown.c\n");

	int count;
	count = 0;

	// Configure the IO switches
	io_switch_setup();

	// Loop and wait for edges to update the count
	while(1){
		if(edge_val & 0x01){
			count++;
			printf("incrementing count : %i\n", count);
		} else if(edge_val & 0x02){
			count--;
			printf("decrementing count : %i\n", count);
		}// else do nothing

		// clear the edge_val to prevent ongoing counting
		edge_val = 0;

		// Output the count to the LEDs
		IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE, count);
	}

	return 0;
} // end main

////////////////////////////////
// io_switch_setup
//
// HW: setup sw0 and sw1 with edge capture interrupts
//
// Enables interrupts and registers the ISR
//
// inputs: none
// outputs: none
/////////////////////////////////
void io_switch_setup(void){
	// Enable interrupts on 2 switches
	IOWR_ALTERA_AVALON_PIO_IRQ_MASK(SW_PIO_BASE, 0x03);

	// Clear any existing interrupts
	IOWR_ALTERA_AVALON_PIO_EDGE_CAP(SW_PIO_BASE, 0x00);

	// Cast the global variable to the required ISR
	// type of pinter - void *
	void * edge_val_ptr;
	edge_val_ptr = (void *) &edge_val;

	// Register the interrupt
	alt_ic_isr_register(SW_PIO_IRQ_INTERRUPT_CONTROLLER_ID,
						SW_PIO_IRQ,
						io_switch_isr,
						edge_val_ptr,
						0x00);
} // end io_sw_setup

////////////////////////////////
// io_switch_isr
//
// isr function to read which switch created the interrupt
// and then set global variable to be used by the program
//
// inputs: a context that points to the global variable (void * pointer)
// outputs: modifies the value of a global variable  - holds switch inteerupt id
// 			01 for sw0, 10 for sw1
/////////////////////////////////
void io_switch_isr(void * context){
	// expect the context passed to be a pointer
	// to the variable to hold the edge capture information
	//
	// create a pointer variable to hold the context
	volatile int * edge_ptr;
	edge_ptr = (volatile int *) context;

	// Read the edge capture register and assign the
	// value to the ptr variable
	*edge_ptr = IORD_ALTERA_AVALON_PIO_EDGE_CAP(SW_PIO_BASE);

	// Added usleep for a sloppy debouncer
	usleep(10000);

	// Clear the edge capture register
	IOWR_ALTERA_AVALON_PIO_EDGE_CAP(SW_PIO_BASE, 0);

	return;
} // end io_switch_isr