/*
 * File:   pwm_fan_controler
 * Author: www.henteko.org
 *
 * Created on 2021/05/23, 11:48
 */

#include <xc.h>

#pragma config FOSC = INTOSCIO
#pragma config WDTE = OFF
#pragma config FCMEN = OFF
#pragma config PWRTE = ON
#pragma config CP = OFF
#pragma config CPD = OFF
#pragma config BOREN = ON
#pragma config MCLRE = OFF

#define _XTAL_FREQ  8000000 

void delay_ms(unsigned int t) {
	for(; t > 0; t--)
		__delay_ms(1);
}

unsigned int get_adc(unsigned char ch) {
	ADCON0bits.ADFM = 1;		// padding right
	ADCON0bits.VCFG = 0;		// VREF=VDD
	ADCON0bits.CHS = ch;		// ADC channel
	ADCON0bits.GO_nDONE = 0;	// ADC GO/^DONE
	ADCON0bits.ADON = 1;		// ADC Enable
	__delay_us(25);
	GO = 1;
	while(GO);
	return (ADRESH << 8) + ADRESL;
}

void set_duty(unsigned int duty) {
	CCPR1L = duty >> 2;
	CCP1CONbits.DC1B = duty & 0b00000011;
}

void main(void) {
	unsigned int duty;
	
	OSCCON = 0b1110000;		// clock 8MHz
    
	ANSEL = 0b1011000;		// ADC Fosc/16. AN3 analog
	CMCON0 = 0b00000111;	// comparator off
	TRISIO = 0b00010000;	// GP4 input  

	CCP1CON= 0b00001100;	// PWM mode
	T2CONbits.T2CKPS = 00;	// prescaler 1/1 8000000/4=0.5us
	T2CONbits.TMR2ON = 1;	// tmr2 on
	PR2 = 124;				// PWM frequency 0.5us * (124 + 1) = 62.5us = 16kHz
	TMR2 = 0;				// tmr2

	set_duty(1023);
	delay_ms(2000);
	
	while(1) {
		duty = get_adc(3);
		set_duty(duty / 2);
	}
}