//*************************************************************
//  BOOST1.c  SAAB 9-3 T5 BCV to T7 BCV valve conversion
//
//  (c) 2016 Escherlogic Inc.   All right reserved.
//
//  By: Stefan Hax  stefan@escherlogic.com 
//
//  You are free to use this at your own risk!
//
//*************************************************************
// ATtiny45 code to convert SAAB 93 T5 boost control valve output
// from the ECU to use the newer signle coil T7 boost control valve
// 
// for T7 valve PWM freq is 50Hz for engine speeds lower than 2500RPM
// and 32Hz for higher engine speeds
// 
// for T5 valve freq is 90Hz for engine speeds lower than 2500RPM
// and 70Hz for higher engine speeds
//
//**********************************************************************
#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
#include <avr/io.h>
#include <avr/interrupt.h>

//********************* Memory Config ******************************************
#define EEPROMMEM __attribute__ ((section (".eeprom")))
uint8_t eeprominit[] EEPROMMEM = {0,0,0,255};    // default eeprom memory settings

#define HFUSEMEM __attribute__ ((section (".hfuse")))
uint8_t hfuseinit[] HFUSEMEM = {0xd6};    // hfuse settings -- protect flash during erase -- BOD = 1.8v

#define LFUSEMEM __attribute__ ((section (".lfuse")))
uint8_t lfuseinit[] LFUSEMEM = {0xe2};    // lfuse settings -- internal RC osc @ 8Mhz

#define EFUSEMEM __attribute__ ((section (".efuse")))
uint8_t efuseinit[] EFUSEMEM = {0xff};    // efuse settings
//******************************************************************************

//************************************************
// Port B I/O assignment
#define T5A_IN		3			// PB3 connected to T5 A coil drive (input)
#define T5B_IN		4			// PB4 connected to T5 B coil drive (input)
#define T7_VALVE	0			// PB0 connected to T7 valve (output)
//***********************************************
#define VALVE_ON	PORTB |= _BV(T7_VALVE)
#define VALVE_OFF	PORTB &= (uint8_t)~_BV(T7_VALVE)

//*********************************************************************************************************
// timer0 in CTC mode to generate 50Hz x 100 and 32Hz x 100 interrupt rates
#define T_SLOW	38
#define T_FAST	24
// with timer1 clock rate @ 15.625KHz(64MHz/4096): Then 90Hz PWM count:173 and 70Hz PWM count:223  
#define SLOW_THRESHOLD	200	

// pwm_speed states:
enum { PWM_FAST=0, PWM_SLOW };

// T5 2-coil input states: 
enum { DC_OFF=0, DC_ON, DC_REST };

// globals
volatile uint8_t pwm_speed, pwm_out, pwm_cnt;
volatile uint8_t dc_state, dc_count, dc_on, dc_calc;

//*********************************************
// valve output ISR
ISR(TIM0_COMPA_vect)
{
	pwm_cnt++;
	if(pwm_cnt >= 100) {
		pwm_cnt = 0;
		OCR0A = (pwm_speed == PWM_FAST)? T_FAST : T_SLOW;	// set the TOP valve for the correct PWM frequency
	}
	
	if(pwm_cnt >= pwm_out) { VALVE_OFF; } else { VALVE_ON; }
}

//*******************************************
// timer1 overflow -- if this ISR is called then there is a dead input!!  -- Reset everything...
ISR(TIM1_OVF_vect)
{
	pwm_speed = PWM_FAST;
	pwm_out = 0;
	dc_state = DC_OFF;
	dc_calc = 0;
}

//*******************************************
// Pin Change ISR (T5A / T5B inputs)
ISR(PCINT0_vect)
{

	switch(dc_state) {
		default:
		case DC_OFF:
			if(PINB & _BV(T5A_IN)) {		// NOT TRUE!!
			} else {				// TRUE!!
				dc_count = TCNT1;
				TCNT1 = 0;
				dc_state = DC_ON;
				dc_calc = 1;			// trigger PWM output calculations
			}
			break;
			
		case DC_ON:
			if(PINB & _BV(T5B_IN)) {		// NOT TRUE!!
			} else {				// TRUE!!
				dc_on = TCNT1;
				dc_state = DC_REST;
			}
			break;
			
		case DC_REST:
			if( PINB & (_BV(T5A_IN) | _BV(T5B_IN)) ) {	// BOTH NOT TRUE!!
				dc_state = DC_OFF;
			}
			break;
	}
}

//***********************************
// initialize...
void init(void)
{
uint16_t n;

	//****** timer0 setup ***************************
	// generate interrupts for bit-bang-PWM output
	// where: 0 -> output OFF
	// and 100 -> output 100%
	TCCR0A = _BV(WGM01);					// CTC mode
	TCCR0B = _BV(CS01) | _BV(CS00);				// 8MHz dix 64
	OCR0A = (pwm_speed == PWM_FAST)? T_FAST : T_SLOW;	// set the TOP valve for the correct PWM frequency
	pwm_out = 5;						// default duty cycle
	TIMSK |= _BV(OCIE0A);					// enable interrupt
	
	//****** T7 Valve setup ************************
	DDRB = _BV(T7_VALVE);					// T7 valve output
	VALVE_OFF;						// turn valve OFF
	

	//******* PLL ***********************************
	// setup for 64MHHz
	PLLCSR = _BV(PLLE);					// enable PLL
	for(n=0; n<1000; n++);					// time delay > 100us
	while(!(PLLCSR & _BV(PLOCK)));				// wait for PLL to lock
	PLLCSR |= _BV(PCKE);					// enable Pclk
	
	//******* timer1 setup **************************
	// divide by 4096
	TCCR1 = _BV(CS13) | _BV(CS12) | _BV(CS10);		// PCK/4096
	TIMSK |= _BV(TOIE1);					// just enable overflow interrupt


	//***** control input ***************************
	// setup port change int
	PCMSK = _BV(T5A_IN) | _BV(T5B_IN);			// enable only PB3 & PB4 for PC Int
	GIMSK |= _BV(PCIE);					// enable PC Int

	//***** global int enable *********************
	sei();							// enable global interrupt
}                                                                                                                

//*************************************
// compute T7 valve PWM signal and set
void pwm_go(void)
{
	if(dc_calc) {						// signal from PCINT0 ISR
		dc_calc = 0;					// clear the flag
		
		if(dc_count) {					//
			if(dc_count > SLOW_THRESHOLD) {		// determine engine speed state..
				pwm_speed = PWM_SLOW;
			} else {
				pwm_speed = PWM_FAST;
			}
			
			pwm_out = (uint8_t)( ((uint16_t)dc_on * 100) / (uint16_t)dc_count);	// compute output PWM 
			
		} else { 					// avoiding div/0
			pwm_speed = PWM_FAST;
			pwm_out = 2;
		}
	}
}

//************************************
// main
int main(void)
{
	init();
	
	while(1) {
		pwm_go();
	}
}
//***** done *************************