//Program to test ADC principles
//One ADC input triggering two LEDs to show if voltage is above or below threshhold set in program
//Written for PIC12F683 to be compiled with the CC5X compiler
//Clock frequency left at 4MHz default
//Copyright David Theunissen 2007 www.flyelectric.ukgateway.net

//PREPROCESSOR section

#include "12F683.H"				//PIC chip file
#include "delay_ms.h"			//Delay function used below

#pragma config = 0b.0.1100.0100	//Brown-out Detect disabled (0)
								//Code Protect off (1)
								//MCLR set to 'Internal' (1)
								//Powerup timer enabled (0)
								//Watchdog timer disabled (0)
								//Oscillator set to INTRCIO (100)
								
//VARIABLES section

#define LED_HIGH 	GPIO.0		//Define pin7 as voltage 'high' LED
#define LED_LOW		GPIO.2		//Define pin5 as voltage 'low' LED

long ADC_VALUE_1;				//Set variable for ADC value of 'pack1' (16bits)
long ADC_TEMP;					//Temporary variable for extracting high bits of ADRESH register


//FUNCTIONS section
	
void main()
{
//Main port settings
	TRISIO0 = 0;				//Sets GP ports to Output (0) and Input (1)
    TRISIO2 = 0;				//as above
    TRISIO3 = 1;				//ADC input
    
    ANS0 = 0;					//Sets ADC port to digital (Output=0) or analogue (Input=1)
    ANS2 = 0;					//as above
    ANS3 = 1;					//ADC input
    
    CMCON0 = 0b.111;			//Switches all 3 comparator ports off
	
//ADC settings
    ADCON0.6 = 0;				//VCFG: Use Vdd for ADC voltage reference
    ANSEL.4 = 1;				//ADCS: Set AD Conversion Clock to Fosc/16
    ANSEL.5 = 0;				//part of above
    ANSEL.6 = 1;				//part of above
    ADCON0.7 = 1;				//ADFM: Right-justify ADC register
	
//Activate ADC
    ADCON0.0 = 1;				//ADON: Turn AD module ON
    ADCON0.2 = 1;				//CHS0: Select input channel to ANS3 only
    ADCON0.3 = 1;				//part of above
    ADIE = 0;					//ADC interrupts disabled
    
    while(1)					//Run ADC continuously
    { 
	//Run ADC
    	delay_ms(1);			//Delay for acquisition capacitor to charge
		ADIF = 0;				//Clear the ADC Complete flag
		ADCON0.1 = 1;			//GO: Start ADC acquisition
		while(!ADIF) continue;	//Wait for conversion to complete (ADIF gets set to 1)

	//Determine complete ADC value				
		ADC_TEMP = ADRESH;				//The ADC produces a 10bit value stored in two 8bit registers
										//ADRESH contains the higher 2 bits of the ADC conversion value
										//This statement moves that value from an 8bit register to 16bit
		ADC_TEMP = ADC_TEMP<<8;			//<<8 moves all bits 8 places left (hence the need for 16bits)
										//The upper 2 bits are now in ADC_TEMP in bits 9 and 10
		ADC_VALUE_1 = ADC_TEMP|ADRESL;	//| is the OR operator to merge lower 8 bits with upper 2
		
	//Indicate result via LEDs									
			if (ADC_VALUE_1 >= 512)	//Have 1k pot and 1k resistors either side (3k total) dividing '5v' Vdd
									//Actual voltages range from 1.652 to 3.226v (Vdd=4.93v)
									//ADC values range from 335 to 662
			{					
			LED_HIGH = 1;		//'High' LED on (pin7)
			LED_LOW = 0;		//'Low' LED off
			}
		else
			{
			LED_HIGH = 0;		//'High' LED off
			LED_LOW = 1;		//'Low' LED on (pin5)
			}

	//Delay to 'debounce' cross-over		
	    delay_ms(50);			//Invokes delay function (eg: 50ms = 0.05 second)

	}							//end while
}								//end main