/*
 *********************************************************************
 * Knihovna:  I2C
 * Projekt:   DUNIT
 * Prekladac: AVR-GCC
 * Autor:     Tomas Kakac (c)2010
 * Datum:     2010-04-08
 * Verze:     1.0
 * Popis:     Knihovna funkci I2C master
 *********************************************************************
 */

#include <inttypes.h>
#include <compat/twi.h>
#include "I2C.h"

#ifndef F_CPU
#define F_CPU	14745600UL				// frekvence hodin CPU
#endif

#define	SCL_CK	100000L					// frekvence hodin I2C

/* Inicializace rozhrani sbernice I2C ----------------------------- */
/* Vstup: -                                                         */
/* Vraci: -                                                         */
/* ---------------------------------------------------------------- */
void i2c_init(void)
{
  TWSR = 0;											// bez predrazene delicky
	TWBR = ((F_CPU/SCL_CK)-16)/2;	// pro stabilni funkci musi byt > 10
}

/* Vystaveni podminky START a vyslani adresy + smeru prenosu ------ */
/* Vstup: adresa I2C zarizeni a smer prenosu                        */
/* Vraci: 0 = zarizeni je dostupne                                  */
/*        1 = neuspesny pristup k zarizeni                          */
/* ---------------------------------------------------------------- */
extern unsigned char i2c_start(unsigned char addr)
{
  uint8_t twst;

	TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);	// vyslani podminky START
  while(!(TWCR & (1<<TWINT)));  // cekani dokud neni prenos kompletni
  twst = TW_STATUS & 0xF8;      // kontrola stavoveho registru TWI
  if ((twst != TW_START) && (twst != TW_REP_START)) 
    return 1;
  TWDR = addr;                  // vyslani adresy zarizeni
  TWCR = (1<<TWINT) | (1<<TWEN);
  while(!(TWCR & (1<<TWINT)));  // cekani na prenos a prijem ACK/NACK
  twst = TW_STATUS & 0xF8;      // kontrola stavoveho registru TWI
  if ((twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK)) 
    return 1;
  return 0;
}

/* Vystaveni podminky START a vyslani adresy + smeru prenosu ------ */
/* Pokud je obvod zaneprazdnen, pouzije se opakovane dotazovani na  */
/* ACK pro cekani dokud neni obvod pripraven                        */
/* Vstup: adresa I2C zarizeni a smer prenosu                        */
/* Vraci: 0 = zarizeni je dostupne                                  */
/*        1 = neuspesny pristup k zarizeni                          */
/* ---------------------------------------------------------------- */
extern void i2c_start_wait(unsigned char addr)
{
  uint8_t twst;

	while (1)
	{
	  TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);	// vyslani podminky START
    while(!(TWCR & (1<<TWINT)));// cekani dokud neni prenos kompletni
    twst = TW_STATUS & 0xF8;    // kontrola stavoveho registru TWI
    if ((twst != TW_START) && (twst != TW_REP_START)) 
      continue;
    TWDR = addr;                // vyslani adresy zarizeni
    TWCR = (1<<TWINT) | (1<<TWEN);
    while(!(TWCR & (1<<TWINT)));// cekani na prenos a prijem ACK/NACK
    twst = TW_STATUS & 0xF8;    // kontrola stavoveho registru TWI
    if ((twst == TW_MT_SLA_NACK) || (twst == TW_MR_DATA_NACK))
		{
		  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
			while(TWCR & (1<<TWSTO)); // podm. STOP a uvolneni sbernice I2C
			continue;
		} 
    break;
	}
}

/* Opakovane vystaveni START a vyslani adresy + smeru prenosu ----- */
/* Vstup: adresa I2C zarizeni a smer prenosu                        */
/* Vraci: 0 = zarizeni je dostupne                                  */
/*        1 = neuspesny pristup k zarizeni                          */
/* ---------------------------------------------------------------- */
extern unsigned char i2c_rep_start(unsigned char addr)
{
  return i2c_start(addr);
}

/* Ukonceni prenosu a uvolneni sbernice I2C ----------------------- */
/* Vstup: -                                                         */
/* Vraci: -                                                         */
/* ---------------------------------------------------------------- */
extern void i2c_stop(void)
{
  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO); //podminka STOP
  while(TWCR & (1<<TWSTO));     // cekani na STOP a uvolneni sbernice
}

/* Vyslani jednoho byte do I2C zarizeni --------------------------- */
/* Vstup: byte, ktery se ma prenest                                 */
/* Vraci: 0 uspesny zapis                                           */
/*        1 neuspesny zapis                                         */
/* ---------------------------------------------------------------- */
extern unsigned char i2c_write(unsigned char data)
{
  uint8_t   twst;
    
  TWDR = data;                  // vyslani dat do adres. zarizeni
  TWCR = (1<<TWINT) | (1<<TWEN);

  while(!(TWCR & (1<<TWINT)));  // cekani na dokonceni prenosu

  twst = TW_STATUS & 0xF8;      // kontrola stavoveho registru TWI
  if (twst != TW_MT_DATA_ACK)
    return 1;
  return 0;
}

/* Cteni jednoho byte ze zarizeni I2C, pozaduje se vicedat -------- */
/* Vstup: -                                                         */
/* Vraci: byte precteny ze zarizeni I2C                             */
/* ---------------------------------------------------------------- */
extern unsigned char i2c_readAck(void)
{
  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA);
	while(!(TWCR & (1<<TWINT)));    
  return TWDR;
}

/* Cteni jednoho byte ze zarizeni I2C, za ctenim nasleduje STOP --- */
/* Vstup: -                                                         */
/* Vraci: byte precteny ze zarizeni I2C                             */
/* ---------------------------------------------------------------- */
extern unsigned char i2c_readNak(void)
{
	TWCR = (1<<TWINT) | (1<<TWEN);
	while(!(TWCR & (1<<TWINT)));
	
  return TWDR;
}