#include "header.h"

#define TWI_PRESCALE_VALUE	1											// can be 1, 4, 16, 64
#define TWI_FREQ			100000UL									// 100kHz I2C

typedef enum {
	START,
	STOP
} I2C_status;
volatile I2C_status i2c_status = START;

void i2c_init(void) {
    TWSR = TWI_PRESCALE_SET(TWI_PRESCALE_VALUE);						// 22.9.3 : (Status Register) set prescaler
    TWBR = ((F_CPU / TWI_FREQ) - 16) / (2 * TWI_PRESCALE_VALUE);		// 22.9.1 : (Bit Rate Register) set SCL frequency (formula from datasheet, 22.5.2)
}

void i2c_start(void) {
	i2c_status = START;
    TWCR = SEND_START_CONDITION;										// 22.9.2 : (Control Register) send Start condition (22.7.1) ! writting 1 to TWINT clears it (set it to 0)
    while (!(TEST(TWCR, TWINT)));										// p225 example code : Wait for TWINT Flag set. This indicates that the START condition has been transmitted

	uint8_t status = TWSR & 0b11111000;									// Table 22-2. Status codes for Master Transmitter Mode
    if (status != TW_START && status != TW_REP_START) {
		return i2c_stop();
    }
}

void i2c_send_addr_w(uint8_t slave_address) {
	if (i2c_status == STOP) {
        return;
    }
	uint8_t addr = (slave_address << 1) | TW_WRITE;					// 22.3.3 : address format SLA+R/W
    TWDR = addr;													// 22.9.4 : (Data Register) load data into TWDR register
    TWCR = SEND_CONTINUE_TRANSMISSION;								// 22.7.1 : Master Transmitter Mode
    while (!(TEST(TWCR, TWINT)));									// 22.7.1 : Wait for TWINT Flag set. This indicates that the SLA+R/W has been transmitted, and ACK/NACK has been received

	uint8_t status = TWSR & 0b11111000;								// Table 22-2 : check status for Transmitter mode, mask prescaler bits
    if (status == TW_MT_SLA_ACK) {									// status 0x18 : slave address transmitted, slave acknoledged (continue transmission)
        return;
    } else if (status == TW_MT_SLA_NACK) {							// status 0x20 : slave address transmitted, slave did not acknoledge (retry or send STOP)
		return i2c_stop();
    } else if (status == TW_MT_ARB_LOST) {							// status 0x38 : Arbitration Lost, Another I2C master took control of the bus (wait for bus to be free and retry)
		return i2c_stop();
    } else {
		return i2c_stop();
    }
}

void i2c_send_addr_r(uint8_t slave_address) {
	if (i2c_status == STOP) {
        return;
    }
	uint8_t addr = (slave_address << 1) | TW_READ;					// 22.3.3 : address format SLA+R/W
    TWDR = addr;													// 22.9.4 : (Data Register) load data into TWDR register
    TWCR = SEND_CONTINUE_TRANSMISSION;								// 22.7.1 : Master Transmitter Mode
    while (!(TEST(TWCR, TWINT)));									// 22.7.1 : Wait for TWINT Flag set. This indicates that the SLA+R/W has been transmitted, and ACK/NACK has been received

	uint8_t status = TWSR & 0b11111000;								// Table 22-3 : check status for Receiver mode, mask prescaler bits
    if (status == TW_MR_SLA_ACK) {									// status 0x40 : slave address transmitted, slave acknoledged (continue transmission)
        return;
    } else if (status == TW_MR_SLA_NACK) {							// status 0x48 : slave address transmitted, slave did not acknoledge (retry or send STOP)
		return i2c_stop();
    } else if (status == TW_MR_ARB_LOST) {							// status 0x38 : Arbitration Lost, Another I2C master took control of the bus (wait for bus to be free and retry)
		return i2c_stop();
    } else {
		return i2c_stop();
    }
}

void i2c_write(unsigned char data) {
	if (i2c_status == STOP) {
        return;
    }
    TWDR = data;													// 22.9.4 : (Data Register) load data into TWDR register
    TWCR = SEND_CONTINUE_TRANSMISSION;								// p225 example code : Load DATA into TWDR Register. Clear TWINT bit in TWCR to start transmission of data
    while (!(TEST(TWCR, TWINT)));									// p225 example code : Wait for TWINT Flag set. This indicates that the DATA has been transmitted, and ACK/NACK has been received

	uint8_t status = TWSR & 0b11111000;								// p225 example code : Check status for Receiver mode. Mask prescaler bits. If status different from MT_DATA_ACK go to ERROR
    if (status != TW_MT_DATA_ACK) {
		return i2c_stop();
    }
}

void i2c_read(void) {
	if (i2c_status == STOP) {
        return;
    }
    // TWDR = data;													// 22.9.4 : (Data Register) load data into TWDR register
    // TWCR = SEND_CONTINUE_TRANSMISSION;								// p225 example code : Load DATA into TWDR Register. Clear TWINT bit in TWCR to start transmission of data
    // while (!(TEST(TWCR, TWINT)));									// p225 example code : Wait for TWINT Flag set. This indicates that the DATA has been transmitted, and ACK/NACK has been received

	// uint8_t status = TWSR & 0b11111000;								// p225 example code : Check status for Receiver mode. Mask prescaler bits. If status different from MT_DATA_ACK go to ERROR
    // if (status != TW_MT_DATA_ACK) {
	// 	return i2c_stop();
    // }
}

void i2c_stop(void) {
    TWCR = SEND_STOP_CONDITION;											// 22.9.2 : send stop condition
	i2c_status = STOP;
}