/************************************************************
 * reads some digital in and make them readable over i2c bus.
 * register 0 -
 *
 *                         +-------+
 *            (RESET) PC6 -|1  O 28|- PC5 (ADC5/SCL)
 *  S3          (RXD) PD0 -|2    27|- PC4 (ADC4/SDA)
 *  S2          (TXD) PD1 -|3    26|- PC3 (ADC3)
 *  S1         (INT0) PD2 -|4    25|- PC2 (ADC2)    S12
 *  S10        (INT1) PD3 -|5    24|- PC1 (ADC1)    S16
 *  S7        (XCK/T0)PD4 -|6    23|- PC0 (ADC0)    S15
 *                    VCC -|7    22|- GND
 *                    GND -|8    21|- AREF
 *  S8  (XTAL2/TOSC2) PB6 -|9    20|- AVCC
 *  S9  (XTAL2/TOSC2) PB7 -|10   19|- PB5 (SCK)
 *  S4           (T1) PD5 -|11   18|- PB4 (MISO)
 *  S5         (AIN0) PD6 -|12   17|- PB3 (MOSI(OC2)
 *  S6         (AIN1) PD7 -|13   16|- PB2 (SS/OC1B)  S14
 *  S11        (ICP1) PB0 -|14   15|- PB1 (OC1A)     S13
 *                         +-------+
 */

#include <avr/io.h>
#include <avr/interrupt.h>
#include <stdarg.h>
#include <stdio.h>

#include <util/delay.h>
#include <util/twi.h>

#include "eprom.h"

#define TWCR_ACK TWCR = (1<<TWEN)|(1<<TWIE)|(1<<TWINT)|(1<<TWEA);
#define TWCR_NACK TWCR = (1<<TWEN)|(1<<TWIE)|(1<<TWINT)
#define TWCR_RESET TWCR = (1<<TWEN)|(1<<TWIE)|(1<<TWINT)|(1<<TWEA)|(1<<TWSTO);  

#define I2C_NUM_REGS 8
#define I2C_DEFAULT_ADDR 0x4F
#define VERSION 1

#define I2C_SREGS_OFFSET 0x20

enum {
	I2C_SREG_VERSION = 0,
	I2C_SREG_CMD,
	I2C_SREG_ADDR,
	I2C_SREG_DIOFFDELAY,
	I2C_SREG_DOOFFDELAY,

	I2C_SREG_MAX
};

enum {
	I2C_CMD_NONE = 0,
	I2C_CMD_EEPROMREAD,
	I2C_CMD_EEPROMWRITE
};

volatile uint8_t i2c_reg;
volatile uint8_t i2c_system[I2C_SREG_MAX];
volatile uint8_t i2c_regs[I2C_NUM_REGS];

//
// i2c slave addresse festlegen und interrupts einschalten
void i2c_slave_init(uint8_t adr) {
	int i;
	
	for (i = 0; i < I2C_NUM_REGS; i++)  {
		i2c_regs[i] = 0;
	}
	
	TWAR = adr << 1;
	TWCR &= ~(1<<TWSTA) | (1<<TWSTO);
	TWCR |= (1<<TWEA) | (1<<TWEN) | (1<<TWIE);

	i2c_reg = 0x0;
	
	sei();
}

ISR (TWI_vect) {
	char data=0;

	switch (TW_STATUS) {
		case TW_SR_SLA_ACK: // 0x60 Slave Receiver, Slave wurde adressiert	
			TWCR_ACK;
			i2c_reg=0xFF;
			break;

		case TW_SR_DATA_ACK: // 0x80 Slave Receiver, ein Datenbyte wurde empfangen
			data=TWDR;
			if (i2c_reg == 0xFF) {
				if(data < I2C_NUM_REGS || (data >= I2C_SREGS_OFFSET && data < I2C_SREGS_OFFSET+I2C_SREG_MAX)) {
					i2c_reg = data;
					TWCR_ACK;
				}
				else 
					TWCR_NACK;
			}
			else {
				if(i2c_reg < I2C_NUM_REGS) {
					i2c_regs[i2c_reg] = data;
					i2c_reg++;
					TWCR_ACK;
				}
				else if (i2c_reg >= I2C_SREGS_OFFSET && i2c_reg < I2C_SREGS_OFFSET+I2C_SREG_MAX) {
					i2c_system[i2c_reg-I2C_SREGS_OFFSET] = data;
					i2c_reg++;
					TWCR_ACK;
				}
				else TWCR_NACK;
			}
			break;

		case TW_ST_SLA_ACK:  //0xA8 Slave wurde im Lesemodus adressiert und hat ein ACK zurückgegeben.
		case TW_ST_DATA_ACK: //0xB8 Slave Transmitter, Daten wurden angefordert
			if (i2c_reg == 0xFF) {
				i2c_reg = 0;
			}	
			if (i2c_reg < I2C_NUM_REGS) {
				TWDR = i2c_regs[i2c_reg];
				i2c_reg++;
				TWCR_ACK;
			}
			else if (i2c_reg >= I2C_SREGS_OFFSET && i2c_reg < I2C_SREGS_OFFSET+I2C_SREG_MAX) {
				TWDR = i2c_system[i2c_reg-I2C_SREGS_OFFSET];
				i2c_reg++;
				TWCR_ACK;
			}
			else TWCR_NACK;
			break;
	
		case TW_SR_STOP:
			TWCR_ACK;
	        break;

		case TW_ST_DATA_NACK: // 0xC0 Keine Daten mehr gefordert 
		case TW_SR_DATA_NACK: // 0x88 
		case TW_ST_LAST_DATA: // 0xC8  Last data byte in TWDR has been transmitted (TWEA = “0”); ACK has been received
		default: 	
		    TWCR_RESET;
			break;
	}
}

/////////////////////////////////////////////////////////////////////////
// 

int main( void ) {
	long int cnt[16] = { 0 };
	unsigned int i;
	unsigned short int inval = 0;
	unsigned short int temp = 0;
	int offdelay;

	//
	// read all variables from eeprom
	i2c_system[I2C_SREG_VERSION] = VERSION;
	i2c_system[I2C_SREG_CMD] = 0;

	i2c_system[I2C_SREG_ADDR] = EEPROM_read(I2C_SREG_ADDR);
	if (i2c_system[I2C_SREG_ADDR] > 0x4f || i2c_system[I2C_SREG_ADDR] < 0x20) {
		i2c_system[I2C_SREG_ADDR] = I2C_DEFAULT_ADDR;
	}

	i2c_system[I2C_SREG_DIOFFDELAY] = EEPROM_read(I2C_SREG_DIOFFDELAY);
	if (i2c_system[I2C_SREG_DIOFFDELAY] == 0 || i2c_system[I2C_SREG_DIOFFDELAY] == 0xFF) {
		i2c_system[I2C_SREG_DIOFFDELAY] = 0x20;
	}

	i2c_system[I2C_SREG_DOOFFDELAY] = EEPROM_read(I2C_SREG_DOOFFDELAY);
	if (i2c_system[I2C_SREG_DOOFFDELAY] == 0) {
		i2c_system[I2C_SREG_DOOFFDELAY] = 0xFF;
	}

	i2c_slave_init (i2c_system[I2C_SREG_ADDR]);

	//
	// system loop
    while( 1 ) {
    	//
    	// digital in registers..
    	offdelay = i2c_system[I2C_SREG_DIOFFDELAY] << 8;

    	i = 0;
		if (PIND & (1 << 2)) cnt[0] = offdelay;
		if (PIND & (1 << 1)) cnt[1] = offdelay;
		if (PIND & (1 << 0)) cnt[2] = offdelay;
		if (PIND & (1 << 5)) cnt[3] = offdelay;
		if (PIND & (1 << 6)) cnt[4] = offdelay;
		if (PIND & (1 << 7)) cnt[5] = offdelay;
		if (PIND & (1 << 4)) cnt[6] = offdelay;
		if (PINB & (1 << 6)) cnt[7] = offdelay;

		if (PINB & (1 << 7)) cnt[8] = offdelay;
		if (PIND & (1 << 3)) cnt[9] = offdelay;
		if (PINB & (1 << 0)) cnt[10] = offdelay;
		if (PINC & (1 << 2)) cnt[11] = offdelay;
		if (PINB & (1 << 1)) cnt[12] = offdelay;
		if (PINB & (1 << 2)) cnt[13] = offdelay;
		if (PINC & (1 << 0)) cnt[14] = offdelay;
		if (PINC & (1 << 1)) cnt[15] = offdelay;

    	// all values
		for (i = 0; i < 16; i++) {
			if (cnt[i] == 0) inval &= ~(1 << (i));
			else {
				cnt[i]--;
				inval |= (1 << (i));
			}
		}

		i2c_regs[0] = (unsigned char) (inval & 0x00FF);
		i2c_regs[1] = (unsigned char) ((inval & 0xFF00) >> 8);

		temp++;
		i2c_regs[2] = (unsigned char) (temp & 0x00FF);
		i2c_regs[3] = (unsigned char) ((temp & 0xFF00) >> 8);


		//
		// system registers
		if (i2c_system[I2C_SREG_CMD] != 0) {
			if (i2c_system[I2C_SREG_CMD] == I2C_CMD_EEPROMREAD) {
				cli();
				i2c_system[I2C_SREG_CMD] = 0;
				for (i = 0; i < I2C_SREG_MAX; i++) {
					i2c_system[i] = EEPROM_read(i);
				}
				sei();
			}

			if (i2c_system[I2C_SREG_CMD] == I2C_CMD_EEPROMWRITE) {
				cli();
				i2c_system[I2C_SREG_CMD] = 0;
				for (i = 0; i < I2C_SREG_MAX; i++) {
					EEPROM_write(i, i2c_system[i]);
				}
				sei();
			}
		}
		i2c_system[I2C_SREG_CMD] = 0;
    }
    return 0;
};