/***************************************************************************
 *   Copyright (C) 01/2009 by Olaf Rempel                                  *
 *   razzor@kopf-tisch.de                                                  *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; version 2 of the License,               *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#include <avr/io.h>
#include <avr/interrupt.h>

#include "alix-usv.h"
#include "eeprom.h"
#include "usi-i2c-slave.h"

extern volatile struct ee_param params;

static const uint8_t adc_mux[] = {
	CH_CURRENT_P, CH_CURRENT_N,
	CH_VOLTAGE_BAT, CH_VOLTAGE_SUP,
};

static volatile uint8_t adc_update;
static volatile int16_t adc_value[3];

enum {
	ADC_CURRENT = 0,
	ADC_UBAT = 1,
	ADC_UIN = 2,
};

static volatile uint8_t sys_state;
enum {
	STATE_IDLE	= 0x01,
	STATE_TEST	= 0x02,
	STATE_CHARGE	= 0x04,
	STATE_DISCHARGE	= 0x08,
	STATE_POWEROFF	= 0x10,
};

static uint32_t adc_buf[4];
ISR(ADC_vect)
{
	static uint8_t cnt;

	/* use result of second conversion (switching ADC-gain needs time..) */
	if (cnt & 0x01) {
		/* moving average filter */
		uint8_t ch = (cnt >> 1);
		adc_buf[ch] = ((adc_buf[ch] * 7) + ((uint32_t)ADC << 8)) /8;
		uint16_t value = (adc_buf[ch] >> 8) + ((adc_buf[ch] & 0x80) ? 1 : 0);

		if (ch == 0 && (adc_buf[0] >= adc_buf[1])) {
			/* charging: positive current = ADC * 1.25 */
			adc_value[ADC_CURRENT] = value + (value >> 2);

		} else if (ch == 1 && (adc_buf[0] < adc_buf[1])) {
			/* discharging: negative current = ADC * -1.25 */
			adc_value[ADC_CURRENT] = -(value + (value >> 2));

		} else if (ch == 2) {
			/* Ubat = (ADC * 21.28) - (Ishunt * 0.1) */
			adc_value[ADC_UBAT] = (value * 21) + ((value * 9) >> 5) - (adc_value[ADC_CURRENT] / 10);

		} else if (ch == 3) {
			/* Uin = ADC * 21.28 */
			adc_value[ADC_UIN] = (value * 21) + ((value * 9) >> 5);

			/* all values updated */
			adc_update = 1;
		}
	}

	/* trigger next conversion */
	cnt = (cnt +1) & 0x07;
	ADMUX = adc_mux[cnt >> 1];
	ADCSRA |= (1<<ADSC);
}

static uint8_t i2c_reg;

void usi_write(uint8_t data, uint8_t bcnt)
{
	/* select register */
	if (bcnt == 0) {
		i2c_reg = data;
		return;
	}

	bcnt--;

	/* reg 0x00, lowbyte -> write control */
	if (i2c_reg == 0x00 && bcnt == 0x00) {
		/* poweroff is always allowed */
		if (data & STATE_POWEROFF)
			sys_state = data;

		/* discharge cmd is never allowed */
		else if (data & STATE_DISCHARGE)
			return;

		/* during discharge nothing is allowed */
		else if (sys_state != STATE_DISCHARGE)
			sys_state = data;

	/* register word 0x20 - 0x26 eeprom parameters */
	} else if (i2c_reg >= 0x20 && i2c_reg <= 0x26) {
		uint8_t *ptr = (uint8_t *)&params;
		uint8_t index = ((i2c_reg - 0x20) << 1) + (bcnt & 0x01);
		ptr[index] = data;

		/* crc field */
		if (i2c_reg == 0x26 && bcnt == 0x01)
			write_parameters();
	}
}

uint8_t usi_read(uint8_t bcnt)
{
	/* snapshot of adc value */
	static int16_t adc_copy;

	/* reg 0x00, lowbyte -> read status */
	if (i2c_reg == 0 && bcnt == 0) {
		return sys_state;

	/* register word 0x10 - 0x12 adc values */
	} else if (i2c_reg >= 0x10 && i2c_reg <= 0x12) {
		if (bcnt == 0x00) {
			adc_copy = adc_value[i2c_reg - 0x10];
			return adc_copy & 0xFF;

		} else {
			return (adc_copy >> 8) & 0xFF;
		}

	/* register word 0x20 - 0x25 eeprom parameters */
	} else if (i2c_reg >= 0x20 && i2c_reg <= 0x25) {
		uint8_t *ptr = (uint8_t *)&params;
		uint8_t index = ((i2c_reg - 0x20) << 1) + (bcnt & 0x01);
		return ptr[index];
	}

	return 0x00;
}

/*
 * the watchdog timer remains active even after a
 * system reset. So disable it as soon as possible.
 * automagically called on startup
 */
void disable_wdt_timer(void) __attribute__((naked, section(".init3")));
void disable_wdt_timer(void)
{
	MCUSR = 0;
	WDTCSR = (1<<WDCE) | (1<<WDE);
	WDTCSR = (0<<WDE);
}

int main(void)
{
	PORTA = I2C_SCL | I2C_SDA;
	DDRA = I2C_SCL | LED_GN;

	DDRB = EN_POWER | EN_CHARGER | EN_TEST;

	/* Disable Digital Inputs */
	DIDR0 = AIN_REF | AIN_CURRENT_N | AIN_CURRENT_P | AIN_VOLTAGE_BAT | AIN_VOLTAGE_SUP;

	/* ADC: freerunning with F_CPU/128 */
	ADMUX = adc_mux[0];
	ADCSRA = (1<<ADEN) | (1<<ADSC) | (1<<ADIF) | (1<<ADIE) | (1<<ADPS2) | (1<<ADPS1) | (1<<ADPS0);

	/* init TWI statemachine */
	usi_statemachine();

	/* read statemachine parameters from eeprom */
	read_parameters();

	sei();

	/* enable power */
	sys_state = STATE_IDLE;
	PORTB = EN_POWER;

	/* wait 1s for moving average filters */
	uint8_t i;
	for (i = 0; i < 50; i++)
		_delay_ms(20);

	while (1) {
		while (!adc_update);
		adc_update = 0;

		/* disable interrupts while using adc_value and params */
		cli();

		/* loss of external power => discharge */
		if (sys_state & (STATE_IDLE | STATE_TEST | STATE_CHARGE))
			if (adc_value[ADC_UIN] < params.uin_loss)
				sys_state = STATE_DISCHARGE;

		/* external power restored => charge */
		if (sys_state & (STATE_DISCHARGE | STATE_POWEROFF))
			if (adc_value[ADC_UIN] > params.uin_restore)
				sys_state = STATE_CHARGE;

		/* battery is low => charge */
		if (sys_state & (STATE_IDLE | STATE_TEST))
			if (adc_value[ADC_UBAT] < params.ubat_low)
				sys_state = STATE_CHARGE;

		switch (sys_state) {
		case STATE_IDLE:
			PORTB = EN_POWER;
			break;

		case STATE_TEST:
			PORTB = EN_POWER | EN_TEST;
			break;

		case STATE_CHARGE:
			PORTB = EN_POWER | EN_CHARGER;

			/* battery is full => idle */
			if (adc_value[ADC_UBAT] > params.ubat_full && adc_value[ADC_CURRENT] < params.ibat_full)
				sys_state = STATE_IDLE;
			break;

		case STATE_DISCHARGE:
			PORTB = EN_POWER;

			/* battery is critical low => poweroff */
			if (adc_value[ADC_UBAT] < params.ubat_critical)
				sys_state = STATE_POWEROFF;
			break;

		case STATE_POWEROFF:
			PORTB = 0x00;
			break;

		default:
			sys_state = STATE_IDLE;
			break;
		}

		/* re-enable interrupts */
		sei();
	}
}