// PIC18F14K50 in C - Versione 0.7a - Febbraio 2012
// Copyright (c) 2010-2012 VincenzoV.net
// Creative Commons | Attribuzione-Condividi allo stesso modo 3.0 Unported.
// Creative Commons | Attribution-Share Alike 3.0 Unported
// https://www.vincenzov.net/tutorial/elettronica-di-base/PIC18F14K50

// Using internal ADC - Interrupt

#include <p18f14k50.h>

#pragma config FOSC = HS         // External crystal oscillator (12 MHz) 
#pragma config PLLEN = ON        // Oscillator multiplied by 4  (48 MHz) 
#pragma config WDTEN = OFF       // Watchdog disabled
#pragma config LVP = OFF         // Disable Low Voltage Programming
#pragma config MCLRE = ON        // Master clear enabled

void High_Int (void);            // ISR function prototype

unsigned char volatile AD_high;           // AD data buffer 2 MSB bits + data ready (1xxx xxx)
unsigned char volatile AD_low;            // AD data buffer 8 LSB bits
unsigned char volatile AD_done_flag;      // AD data in buffer

#pragma code high_vector = 0x08   // Setup interrupt vector

void interrupt (void) 
{ _asm GOTO High_Int _endasm }   // Jump to ISR function (in-line assembler)

#pragma code                     // Back to normal code

#pragma interrupt High_Int
void High_Int (void) 
{ //PORTCbits.RC4 = 1;            // RC4 up: start of interrupt time - Debug and timing
  if (PIR1bits.ADIF )             // Interrupt from ADC?
    {AD_high = ADRESH;            // Get high 2 bits and save in buffer
     AD_low = ADRESL;             // Get low 8 bits and save in buffer
     AD_done_flag = 1;            // Data in buffer
     ADCON0bits.GO = 1;           // Start new conversion
     PIR1bits.ADIF = 0;           // Clear interrupt status
    }
  //PORTCbits.RC4 = 0;            // RC4 up: stop of interrupt time - Debug and timing
}

void main(void)
{ unsigned int voltage;
  
  TRISC = 0x00;	        // Set PORTC as Output
  ANSEL = 0;            // Set as Digital I/O
  ANSELH = 0;           // Set as Digital I/O

  TRISBbits.TRISB4 = 1; // Set RB4  (pin 13, aka AN10) to input
  ANSELHbits.ANS10 = 1; // Set AN10 (pin 13, aka RB4) to analog
  
  ADCON0=0b00101001;   // Channel AN10 (xx10 10xx), Enable ADC (xxxx xxx1)
  ADCON1=0b00000000;   // VDD and VSS as voltage reference (xxxx 0000)
  ADCON2=0b10001110;   // Right justify result (1xxx xxx), 2 TAD delay (xx00 1xxx), TAD = 1.33 us (Fck/64 = 0.75 Mhz) (xxxx x110) 

  RCONbits.IPEN = 1;       // Enable priority levels on interrupts
  PIE1bits.ADIE = 1;       // Enable interrupt from ADC
  IPR1bits.ADIP = 1;       // Set high priority interrupt
  PIR1bits.ADIF = 0;       // Clear interrupt status to avoid automatic interrupt ad "boot time"
  INTCONbits.GIEH = 1;     // Enables high priority interrupts
  
  ADCON0bits.GO = 1;       // Start first conversion 

  while (1)
  { //PORTCbits.RC5 = 0;     // RC5 down: idle time - Debug and timing
    
    while (!AD_done_flag);   // Wait new data from ADC
    
    //PORTCbits.RC5 = 1;     // RC5 up: running time - Debug and timing
        
    voltage = ( (unsigned int)AD_high << 8) + AD_low; 
                                 // Convert data from ADC to 0-1023 integer     
    AD_done_flag=0;              // Clear semaphore 
       
    PORTC = (voltage >> 6) & 0x0F;  // Display 4 MSB

  }

}