/* 
 * File:   cointoss.c
 * Author: justin
 *
 * Created on 17 June 2013, 11:19
 */

#include <xc.h>
#include <pic12f1840.h>

#include <stdint.h>
#include <stdlib.h>

#pragma config CP = OFF         // Flash Program Memory Code Protection (Program memory code protection is disabled)
#pragma config CPD = OFF        // Data Memory Code Protection (Data memory code protection is disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable (Brown-out Reset enabled)
#pragma config CLKOUTEN = OFF   // Clock Out Enable (CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin)
#pragma config IESO = ON        // Internal/External Switchover (Internal/External Switchover mode is enabled)
#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enable (Fail-Safe Clock Monitor is enabled)

// CONFIG2
#pragma config WRT = OFF        // Flash Memory Self-Write Protection (Write protection off)
#pragma config PLLEN = ON       // PLL Enable (4x PLL enabled)
#pragma config STVREN = ON      // Stack Overflow/Underflow Reset Enable (Stack Overflow or Underflow will cause a Reset)
#pragma config BORV = LO        // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (Vbor), low trip point selected.)
#pragma config LVP = ON         // Low-Voltage Programming Enable (Low-voltage programming enabled)


/* default clock is 500kHz */
#define _INT_OSC 500000L
#define _XTAL_FREQ _INT_OSC


uint8_t random_byte = 0xB4;

void dorand(void)
{
    asm("BCF STATUS,0");
    asm("RRF _random_byte,W");
    asm("BTFSC STATUS,0");
    asm("XORLW 0xB4");
    asm("MOVWF _random_byte");
}

#define CHECK_MSEC 5        // sample key every 5 mS
#define PRESS_MSEC 10       // stable before presses
#define RELEASE_MSEC 100    // stable before released

void KeyPress(void)
{
    uint8_t count = PRESS_MSEC / CHECK_MSEC;

    while (count > 0) {
        if (PORTAbits.RA2 == 0)
            count--;
        else
            count = PRESS_MSEC / CHECK_MSEC;
        __delay_ms(CHECK_MSEC);
    }
    count = RELEASE_MSEC / CHECK_MSEC;
    while (count > 0) {
        if (PORTAbits.RA2 == 1)
            count--;
        else
            count = RELEASE_MSEC / CHECK_MSEC;
        __delay_ms(CHECK_MSEC);
    }
}

/*
 * main function
 */
int main(int argc, char** argv) {

    /* 12.0 page 101 setup the ports */
    TRISAbits.TRISA0 = 0;
    TRISAbits.TRISA1 = 0;
    TRISAbits.TRISA2 = 1;

    /* disable analog features */
    ANSELAbits.ANSA0 = 0;
    ANSELAbits.ANSA1 = 0;
    ANSELAbits.ANSA2 = 0;

    /* page 107 enable weak pullup on A2 */
    WPUAbits.WPUA2 = 1;
    OPTION_REGbits.nWPUEN = 0;

    while (1) {
        // Wait for the button to press (go low)
        KeyPress();
        // toss the coin
        dorand();
        // set the lights
        if (random_byte & 0x01) {
            PORTAbits.RA0 = 1;
            PORTAbits.RA1 = 0;
        } else {
            PORTAbits.RA0 = 0;
            PORTAbits.RA1 = 1;
        }
    }

    return (EXIT_SUCCESS);
}