// Freq.C
//
// Measure the frequency of a signal on RC0
// Measuring as cycles per second
// Output a 1kHz square wave on RC1 as a test signal
// Timer0 interrupts every 1 second
// Timer1 is a counter.  Counts edges on RC0

// Global Variables

const unsigned char MSG0[21] = "Freq.C              "; 
const unsigned char MSG1[21] = "Hz                  ";     

unsigned int T0, T1, T2;

// Subroutine Declarations
#include <pic18.h>

// Subroutines
#include        "lcd_portd.c"

// High-priority service
void interrupt IntServe(void)
{
   if (TMR0IF) {       // interrupt every 1 second
      TMR0 = -39250;
      T0 += 1;
      T2 = T1;
      T1 = TMR1;
      TMR0IF = 0;
      }
   if (TMR1IF) {
      TMR1IF = 0;
      }
   if (TMR2IF) {
      RC1 = !RC1;
      TMR2IF = 0;
      }
   if (TMR3IF) {
      TMR3IF = 0;
      }
   }
  
          
// Main Routine

void main(void)
{
   unsigned char i;
   unsigned int Hz;

   TRISA = 0;
   TRISB = 0;
   TRISC = 0;
   TRISD = 0;
   TRISE = 0;
   ADCON1 = 0x0F;

   LCD_Init();                  // initialize the LCD

   LCD_Move(0,0);  for (i=0; i<20; i++) LCD_Write(MSG0[i]);
   LCD_Move(1,0);  for (i=0; i<20; i++) LCD_Write(MSG1[i]);

   Wait_ms(100);

// set up Timer0 for PS = 257
   T0CS = 0;
   T0CON = 0x87;
   TMR0ON = 1;
   TMR0IE = 1;
   TMR0IP = 1;
   PEIE = 1;
// set up Timer1 for PS = 1
   T1CON = 0x81;
   TMR1ON = 1;
   TMR1IE = 0;
   TMR1IP = 0;
   PEIE = 0;
   TMR1CS = 1;
   TRISC0 = 1;
// set up Timer2 for 0.5ms
   T2CON = 0x4D;
   PR2   = 124;
   TMR2ON = 1;
   TMR2IE = 1;
   TMR2IP = 1;
   PEIE = 1;

// turn on all interrupts
   GIE = 1;
   TMR0 = 0;
   TMR1 = 0;
   T0 = 0;
   T1 = 0;
   T2 = 0;


   while(1) {
      Hz = T1 - T2;
      
      LCD_Move(0,8);  LCD_Out(T0, 5, 0);
      LCD_Move(1,8);  LCD_Out(Hz, 5, 0);
  
      }      


   }