///////////////////////////////////
//
// lab4_base project
//
// created 7/13/21 by tj
// rev 0
//
///////////////////////////////////
//
// Base program for Lab 4
//
// interrupt based counter with debounce
// that flashes an LED based on the current count value
//
///////////////////////////////////

#include "mbed.h"
#include <stdio.h>

#define T_FLASH 250000  // in us - 0.25s
#define T_BOUNCE 5000   // in us - 5ms
#define T_WAIT 4000000  // in us - 4 sec

// function prototypes (declaration)
void counter_isr(void);
void flash_led(volatile int * cnt_ptr);

// Global HARDWARE Objects
// create an interrupt object for Pin D4
InterruptIn Button(D4);
// create an output object for pin D5 for the LED
DigitalOut MyLED(D5);

// global variables for ISR
// note it is defined as volatile since it can
// change without main knowing it - volatile
// forces it to be read from memory each time
// instead of from a CPU register
volatile int cnt;

int main(void){
    setbuf(stdout, NULL);   // disable buffering

    // splash 
    printf("\n\nLab4_base - example for EE2905\n");
    printf("Using Mbed OS version %d.%d.%d\n\n", 
            MBED_MAJOR_VERSION, MBED_MINOR_VERSION, MBED_PATCH_VERSION);

   // attach the isr
   Button.fall(&counter_isr);
   
   // initialize the count
   cnt = 0;
   
   // intilaize the led to off
   MyLED.write(0);
   
   // create a waiting loop
   while(1){
       wait_us(T_WAIT);
       printf("The current count is: %i\n", cnt);
       flash_led(&cnt);
   } // end while

   return 0;
}// end main

void flash_led(volatile int * cnt_ptr){
    // assume LED is already off so can just toggle
    int i;
    for(i = 0; i < (2 * *cnt_ptr); i++){
        MyLED.write(!MyLED.read());
        wait_us(T_FLASH);
    }// end for
    
    return;
}// end flash_led

void counter_isr(void){
    // interrupt service routine for counter
    // debounces the pin and increments the cnt 
    
    ///////////////////////////////////
    // Debounce section
    //
    uint8_t pinval_1;
    uint8_t pinval_2;
    uint8_t valid;
    
    // first check
    pinval_1 = Button.read();
    
    // allow bounce to complete
    wait_us(T_BOUNCE);  // debounce
                        // terrible way to solve the problem
                        
    // second check
    pinval_2 = Button.read();
    
    // set "valid" if not a bounce and value is 0
    if(pinval_1 == pinval_2)
        valid = !pinval_1;
    //
    ///////////////////////////////////////
        
    ///////////////////////////////////////
    // counter increment section
    //
    // increment if valid
    cnt += valid;
    //
    ///////////////////////////////////////

    return;
} // end counter_isr