/* Firmware for the Temperaure fan controller    */
/* Version 1.2, March, 2006                      */
/* Jos van Eijndhoven  (jos@vaneijndhoven.net)   */
/*                                               */
/* Intended for compilation with the (freeware)  */
/* CC5X compiler, version 3.2                    */
/* see:  http://www.bknd.com/cc5x/index.shtml    */

/********************************************************************/
/* Note: before programming (erasing) a 16F676 device, first read   */
/* its CONFIG register and its last (0x3ff) program word!           */
/* These contain factory-programmed calibration values,             */
/* that become lost by (re-)programming!                            */
/* 1st sample: read last program word=343C config:'bandgap midhigh' */
/*                                                                  */
/* Operation:                                                       */
/* TMR0 is used to count up, driven by the internal oscillator.     */
/* In 'set_fans()' the counter value is compared with target values */
/* to create PWM output signals.                                    */
/* Four analog inputs are sampled: three LM60 temperature sensors   */
/* and one 'minimum fan speed' setting.                             */
/* At TMR0 wrap-around all PWM outputs are activated and a limited  */
/* amount of computation is done. During the TMR0 loop, the PWM     */
/* outputs are reset one-by-one.                                    */
/* The PWM frequency can be adjusted with the TMR0 prescaler,       */
/* typically between 64 and 512 Hz.                                 */
/* A global 'time' is maintained for a slow reduction of fan speed, */
/* avoiding control loop instability. Note that this notion of time */
/* floats with the TMR0 prescaler.                                  */
/********************************************************************/

#include <16F676.h>

/* config 13,12 have bandgap calibration value */
#pragma config =0x21c5 /* INTOSC oscillator, with clkout, do BOD, PWRT, no WDT, no MCLR */
#pragma config ID=0xfa01

// PORTA
bit icspdat    @ PORTA.0; // p13: ICSPDAT
bit icspclk    @ PORTA.1; // p12: ICSPCLK, and reference at half vdd (2.5V)
bit minrpm     @ PORTA.2; // p11: AN2
bit mclr       @ PORTA.3; // p04:
bit clkout     @ PORTA.4; // p03:
bit leda       @ PORTA.5; // p02:

// PORTC
bit temp1      @ PORTC.0; // p10: AN4
bit temp2      @ PORTC.1; // p09: AN5
bit temp3      @ PORTC.2; // p08: AN6
bit fan3       @ PORTC.3; // p07:
bit fan2       @ PORTC.4; // p06:
bit fan1       @ PORTC.5; // p05:

bit ADCgo      @ ADCON0.1;

// PWMFREQ is 0,1,2,3, for a PWM frequency of resp. 512Hz, 256Hz, 128Hz, 64Hz
#define PWMFREQ 3

uns8 fanspeed[4];  // [0] is used for LED output, showing current max temperature
uns8 fansample[4]; // [0] is used for sampling min_speed 

uns8 calibrate_clk( void);

void pic_init( void)
{
	/* PORTA */
	TRISA = 0x07; // A.0 to A.2 are inputs
	PORTA = 0;
	ADCON0= 0x41; // left-justified, ext Vref, AD power-up
	ADCON1= 0x50; // rate Fosc/16
	ANSEL = 0x74; // AN6,5,4,2 are analog

	/* PORTC */
	TRISC = 0x07; /* portC 0,1,2 are input */
	PORTC = 0x3f; /* fans on */

    /* TMR0 will wrap at about 500 Hz (or 250, or 125, or 60Hz) */
	OPTION_REG = 0x82 + PWMFREQ; /* no pull-up portA, TMR0 on clk, prescale=8 */

	OSCCAL = calibrate_clk(); /* calibrate on-chip oscillator */
	T1CON  = 0x00; 
    GIE = 0;    /* no interrupts allowed */
}

void ad_input( uns8 sel)
{
	switch (sel)
	{
	   case 1:  ADCON0 = 0xd1; break; // AN4, Vref=extern, Right-justified
	   case 2:  ADCON0 = 0xd5; break; // AN5, Vref=extern, Right-justified
	   case 3:  ADCON0 = 0xd9; break; // AN6, Vref=extern, Right-justified
	   default: ADCON0 = 0x09; // minRPM: AN2, Vref=Vdd, Left justified
	}
	/* after setting ADCON, we need some time to stabilize the analog input */
}

void set_fans( void)
{
	while (!T0IF)
	{
		mclr = 0;
		if (TMR0 > fanspeed[0])
			leda = 0; // off
		if (TMR0 > fanspeed[1])
			fan1 = 0; // off
		if (TMR0 > fanspeed[2])
			fan2 = 0;
		if (TMR0 > fanspeed[3])
			fan3 = 0;
	}
	T0IF = 0;
	leda = 1;
	mclr = 1;
	PORTC = 0xff; // all fans on
}

void scale( uns8 sel)
{
	/* AD full scale (Vref) is 1.6V, 64 LSB counts is 100mV  */
	/* 580mV -> fan off, 680mV -> fan full on */
	/* 580mV/1.6mV = 362; mod 256 = 106 counts */
		
	uns8 base;
	
	if (sel == 0) // global min fan speed, at ADC full scale
	{
		fansample[0] = ADRESH; // was left-justified	
	} else 
	{   // LM60 temp sensor input, right-justified
		if ((ADRESH == 0) || ((ADRESH == 1) && (ADRESL < 220)))
			fansample[sel] = 0;
		else if ((ADRESH >= 3) || ((ADRESH == 2) && (ADRESL >= 28)))
			fansample[sel] = 255;
		else
		{
	    	base = ADRESL - 220; // min 0 && max 63
			fansample[sel] = base << 2;
		}
	}
}

uns8 time;
void damp( uns8 sel)
{
	uns8 minspeed, mysample;

	
	if (sel == 0) // set led to highest current temp
	{   // led-color (green-red) is created by fanspeed[0] value
		
		fanspeed[0] = fansample[1];
		if (fansample[2] > fanspeed[0])
			fanspeed[0] = fansample[2];
		if (fansample[3] > fanspeed[0])
			fanspeed[0] = fansample[3];
		return;
	}

	// else, sel=[1,2,3], denotes actual fan
	minspeed = fansample[0]; // [0] refers here to analog input 'minspeed' setting
	mysample = fansample[sel]; // scaled temp sensor value for this fan
	
	if (minspeed >= mysample)
		mysample = minspeed;
				
	// higher temp? then increase fan speed immediatly
	if (mysample >= fanspeed[sel]) 
	{
		fanspeed[sel] = mysample;
		return;
	}
	
	// else, decrease fanspeed slowly: full-to-zero (256 cnts) in 500sec
	if (fanspeed[sel] == 0) // fan stands still already
		return;

	if (time == 0)
		fanspeed[sel] -= 1;
}

void main( void)
{
	uns8 sel;
	
	pic_init();
	time = 0;

	while (1)
	{
		time += (4<<PWMFREQ); // incr at average rate of one per 125Hz
		
		for (sel = 0; sel < 4; sel+=1)
		{
			set_fans();
			ad_input(sel);
			set_fans();
			ADCgo = 1;
			set_fans();
			scale(sel);
			set_fans();
			damp(sel);
		}
	}
}

#pragma origin 0x3ff
uns8 calibrate_clk( void)
{
	return 0x3c; // calibrated value, taken from chip read
}