Zobrazenie zdroja stránky I2C.c

<source lang="c">
/*
 * I2C.c
 *
 * Created: 15.01.2013 19:05:05
 *  Author: Tomáš Statečný
 */ 

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

#include "I2C.h"
#include "lcd.h"

//Zadefinovanie CPU fekvencie v Hz pokial nie je dana
#ifndef F_CPU
#define F_CPU 16000000UL
#endif

//Zadefinovanie I2C frekvencie v Hz
#define SCL_CLOCK  100000L

//Inicializacia I2C
void i2c_init(void)
{
  TWSR = 0;                         //No prescaler
  TWBR = ((F_CPU/SCL_CLOCK)-16)/2;  //must be > 10 for stable operation
}

//Zadefinovanie vstupov a vystupov
#define SDA_I  (DDRC &= ~(1<<4))								//Nastavenie 4bit DDRC na citanie (SDA)
#define SCL_O  (DDRC |= (1<<5))									//Nastavenie 5bit DDRC na zapis (SCL)
#define SDA_O  (DDRC |= (1<<4))									//Nastavenie 4bit DDRC na zapis (SDA)

//Nastavovanie pinov
#define SETBIT_SCL      (PORTC |= (1<<5))							//Zapis log.1 na pin 5 PORTC (SCL)
#define CLEARBIT_SCL    (PORTC &= ~(1<<5))							//Zapis log.0 na pin 5 PORTC (SCL)

#define SETBIT_SDA       (PORTC |= (1<<4))							//Zapis log.1 na pin 4 PORTC (SDA)
#define CLEARBIT_SDA    (PORTC &= ~(1<<4))							//Zapis log.0 na pin 4 PORTC (SDA)
#define CHECKBIT_SDA    (PORTC & (1<<4))							//Zistenie stavu na pin 4 PORTC (SDA)

//Funkcia na meranie teploty alebo vlhkosti pre snimac SHT11
unsigned Measure(char CMD){
	char i;
	char j = 0x80;
	unsigned hodnot = 0;

	SDA_O;
	SETBIT_SDA;
	_delay_us(5);
	SCL_O;
	CLEARBIT_SCL;
	_delay_ms(100);

	//Reset merania
	for(i=0; i<10; i++){
		
		SDA_O;
		SETBIT_SDA;
		_delay_us(5);
		SCL_pulse();
	}

	//Incializacia prenosu
	SDA_O;
	CLEARBIT_SDA;
	_delay_us(5);

	SCL_O;
	SETBIT_SCL;
	_delay_ms(5);
	SCL_O;
	CLEARBIT_SCL;
	_delay_ms(5);


	SDA_O;
	CLEARBIT_SDA;
	_delay_us(5);
	SCL_pulse();

	SDA_O;
	SETBIT_SDA;
	_delay_us(5);

	SCL_O;
	SETBIT_SCL;
	_delay_ms(5);
	SCL_O;
	CLEARBIT_SCL;
	_delay_ms(5);

	_delay_ms(20);
	
	//Adresa prikazu
	for(i=0; i<8; i++){

		SDA_O;
		if(!(j & CMD)) CLEARBIT_SDA;
		
		else SETBIT_SDA;

		_delay_us(5);
		SCL_pulse();

		j >>= 1;
	}

	//Overie ACK bitu
	SDA_I;
	SCL_pulse();

	if(CHECKBIT_SDA) return 0;

	SCL_O;
	CLEARBIT_SCL;
	_delay_ms(100);

	SDA_I;
	while(!CHECKBIT_SDA);

	//Pockaj, dokial sa neprenesu data
	SDA_I;
	while(CHECKBIT_SDA);

	//Vycitanie prveho Byte
	for(i=0; i<8; i++){
		hodnot <<= 1;

		SDA_I;
		if(CHECKBIT_SDA){
			hodnot |= 1;
			_delay_us(5);
			SCL_pulse();
		}
	}

	//Odoslanie ACK bitu
	SDA_O;
	CLEARBIT_SDA;
	_delay_us(5);
	SCL_pulse();
	
	//Vycitanie druheho Byte
	for(i=0; i<8; i++){
		hodnot <<= 1;

		SDA_I;
		if(CHECKBIT_SDA){
			hodnot |= 1;
			_delay_us(5);
			SCL_pulse();
		}
	}
	
	return hodnot;										//Vrati hodnotu bez kontrolneho suctu
}

//Zadefinovanie jednej periody SCL
int SCL_pulse(){

	SCL_O;
	CLEARBIT_SCL;
	_delay_ms(5);
	SCL_O;
	SETBIT_SCL;
	_delay_ms(5);
	return 0;
}