/******* T1.c ******************
 *
 * Use Fosc = 4 MHz for Fcpu = Fosc/4 = 1 MHz.
 * Sleep for 16 ms (nominal), using watchdog timeout for wakeup.
 * Toggle RC2 output every 16 milliseconds for measuring looptime with scope.
 * Blink LED on RD4 for 16 ms every four seconds.
 * Check pushbutton and turn on LED continuously while it is pressed.
 *
 *             Current draw = 4 uA (with LED and LCD switched off)
 *
 ******* Program hierarchy *****
 *
 * main
 *  Initial
 *  BlinkAlive
 *  Pushbutton
 *
 *******************************
 */

#include <p18f4321.h>           // Define PIC18LF4321 registers and bits

/*******************************
 * Configuration selections
 *******************************
 */

#pragma config OSC = INTIO1     // Use internal osc, RA6=Fosc/4, RA7=I/O
#pragma config PWRT = ON        // Enable power-up delay
#pragma config LVP = OFF        // Disable low-voltage programming
#pragma config WDT = OFF        // Disable watchdog timer initially
#pragma config WDTPS = 4        // 16 millisecond WDT timeout period, nominal
#pragma config MCLRE = ON       // Enable master clear pin
#pragma config PBADEN = DIG     // PORTB<4:0> = digital
#pragma config CCP2MX = RB3     // Connect CCP2 internally to RB3 pin
#pragma config BOR = SOFT       // Brown-out reset controlled by software
#pragma config BORV = 3         // Brown-out voltage set for 2.1V, nominal
#pragma config LPT1OSC = OFF    // Deselect low-power Timer1 oscillator

/*******************************
 * Global variables
 *******************************
 */
unsigned int DELAY;             // Counter for obtaining a delay
unsigned char ALIVECNT;         // Counter for blinking "Alive" LED
                     
/*******************************
 * Constant strings
 *******************************
 */

/*******************************
 * Variable strings
 *******************************
 */

/*******************************
 * Function prototypes
 *******************************
 */

void Initial(void);
void BlinkAlive(void);
void Pushbutton(void);

/*******************************
 * Macros
 *******************************
 */
#define Delay(x) DELAY = x; while(--DELAY){ Nop(); Nop(); }

/////// Main program //////////////////////////////////////////////////////////

/*******************************
 * main
 *******************************
 */

void main()
{
   Initial();                   // Initialize everything
   while (1)
   {
      PORTCbits.RC2 = !PORTCbits.RC2;  // Toggle pin, for measuring loop time
      BlinkAlive();             // Blink "Alive" LED
      Pushbutton();             // Turn on LED while pushbutton is pressed
      Sleep();                  // Sleep, letting watchdog timer wake up chip
      Nop();
   }
}

/*******************************
 * Initial
 *
 * This function performs all initializations of variables and registers.
 *******************************
 */

void Initial()
{
   OSCCON = 0b01100010;         // Use Fosc = 4 MHz (Fcpu = 1 MHz)
   ADCON1 = 0b00001011;         // RA0,RA1,RA2,RA3 pins analog; others digital
   TRISA = 0b00001111;          // Set I/O for PORTA
   TRISB = 0b01000100;          // Set I/O for PORTB
   TRISC = 0b10000000;          // Set I/O for PORTC
   TRISD = 0b10000100;          // Set I/O for PORTD
   TRISE = 0b00000010;          // Set I/O for PORTE
   PORTA = 0;                   // Set initial state for all outputs low
   PORTB = 0;
   PORTC = 0;
   PORTD = 0b00100000;          // except RD5 that drives LCD interrupt
   PORTE = 0;
   Delay(50000);                // Pause for half a second
   RCONbits.SBOREN = 0;         // Now disable brown-out reset
   ALIVECNT = 247;              // Blink immediately
   WDTCONbits.SWDTEN = 1;       // Enable watchdog timer
}

/*******************************
 * BlinkAlive
 *
 * This function briefly blinks the LED every four seconds.
 * With a looptime of about 16 ms, count 250 looptimes
 *******************************
 */

void BlinkAlive()
{
   PORTDbits.RD4 = 0;           // Turn off LED
   if (++ALIVECNT == 250)       // Increment counter and return if not 250
   {
      ALIVECNT = 0;             // Reset ALIVECNT
      PORTDbits.RD4 = 1;        // Turn on LED for 16 ms every 4 secs
   }
}

/*******************************
 * Pushbutton
 *
 * This function overrides the role of the BlinkAlive function and turns on
 * the LED for the duration of a pushbutton press.
 *******************************
 */

void Pushbutton()
{
   PORTEbits.RE0 = 1;           // Power up the pushbutton
   Nop();                       // Delay one microsecond before checking it
   if (!PORTDbits.RD7)          // If pressed
   {
      PORTDbits.RD4 = 1;        //  turn on LED
   }
   PORTEbits.RE0 = 0;           // Power down the pushbutton
}