Zbernica i2c

I²C
Type	Bus
Production history
Designer	Philips Semiconductor, known today as NXP Semiconductors
Designed	1982; 34 years ago
Data
Signal	Open drain
Width	1 bit (SDA) + clock (SCL)
Bitrate	0.1 / 0.4 / 1.0 / 3.4 / 5.0 Mbit/s (depending on mode)
Protocol	Serial, Half Duplex

I²C (Inter-Integrated Circuit), pronounced I-squared-C, is a multi-master, multi-slave, single-ended, serial computer bus invented by Philips Semiconductor (now NXP Semiconductors). It is typically used for attaching lower-speed peripheral ICs to processors and microcontrollers. Alternatively I²C is spelled I2C (pronounced I-two-C) or IIC (pronounced I-I-C).

Since October 10, 2006, no licensing fees are required to implement the I²C protocol. However, fees are still required to obtain I²C slave addresses allocated by NXP.

Several competitors, such as Siemens AG (later Infineon Technologies AG, now Intel mobile communications), NEC, Texas Instruments, STMicroelectronics (formerly SGS-Thomson), Motorola (later Freescale, now merged with NXP), Nordic Semiconductor and Intersil, have introduced compatible I²C products to the market since the mid-1990s.

SMBus, defined by Intel in 1995, is a subset of I²C that defines the protocol use more strictly. One purpose of SMBus is to promote robustness and interoperability. Accordingly, modern I²C systems incorporate some policies and rules from SMBus, sometimes supporting both I²C and SMBus, requiring only minimal reconfiguration either by commanding or output pin use.

Literatúra

• Official I2C Specification Version 6 http://www.nxp.com/documents/user_manual/UM10204.pdf
• Official List of assigned NXP / Philips I2C addresses http://www.diolan.com/downloads/i2c-address-allocation-table.pdf

• Podrobný článok na Wikipedii: https://en.wikipedia.org/wiki/I%C2%B2C
  • Pseudokod bitbang i2c https://en.wikipedia.org/wiki/I%C2%B2C#Example_of_bit-banging_the_I.C2.B2C_Master_protocol
  • Procyon SW library http://www.procyonengineering.com/embedded/avr/avrlib/docs/html/i2csw_8c-source.html
  • Bitbanging by hand http://hackaday.com/2013/08/11/bitbanging-i2c-by-hand/
  • http://hackaday.com/2015/06/25/embed-with-elliot-i2c-bus-scanning/
  • http://howtomechatronics.com/tutorials/arduino/how-i2c-communication-works-and-how-to-use-it-with-arduino/

• Arduino TWI Library https://www.arduino.cc/en/Reference/Wire

• M24C02 Datasheet
• Mitchell Kahn: Programming the i2c interface. Dr. Dobb's Journal, June 1992.

Datasheets

• AT24C02 EEPROM memory
• BlinkM Smart RGB LED

Vsetko mozne k zbernici i2c (mozno presunut na stranku Category):

• http://www.i2c-bus.org/
• Analyzator: Bus Pirate + Logic Sniffer OLS:
  • http://dangerousprototypes.com/docs/Logic_analyzer_mode
  • https://pixhawk.org/dev/bus_debugging_with_logic_analyzer
  • http://www.hobbytronics.co.uk/bus-pirate-logic-sniffer
  • http://www.hobbytronics.co.uk/bus-pirate

Ukazkove programy (pre Arduino):

• Jednoduchy zapis
• Jednoduche citanie (vyzaduje aj zapis)
• Jednoduchy scan zbernice http://playground.arduino.cc/Main/I2cScanner
• Komplexny i2c scanner https://github.com/RobTillaart/Arduino/tree/master/sketches/MultiSpeedI2CScanner

K. Zbernica i2c: EEPROM

Prečítajte obsah predloženej pamäti EEPROM a zobrazte na PC.

#include <avr/interrupt.h>  
#include <stdlib.h>
#include <avr/io.h>
#include <util/delay.h>
#include <util/twi.h>
#include <stdio.h>

//#include "lcd.h"
#include "Uart_ch.h"

unsigned char RD_EEprom(unsigned char adr_RAM);
void WR_EEprom(unsigned char adr_IC,unsigned char adr_pocitadlo);
void obsluha_Stav_Aut_I2C(void);



#define ADR_IC_WR		0xA0   	// EEPROM Adresa IC+WR
#define ADR_IC_RD		0xA1   	// EEPROM Adresa IC+RD



volatile  unsigned char	buffer_I2C[10];	// buffer pre obsluhu I2C
	




FILE mystdout_Uart = FDEV_SETUP_STREAM(sendchar, NULL, _FDEV_SETUP_WRITE);


void WR_EEprom(unsigned char adr_IC,unsigned char adr_pocitadlo)
{ 	// nastavenie globalnych premennych

	buffer_I2C[0]=adr_IC;	// Adr obvodu + wr
	buffer_I2C[1]=adr_pocitadlo;	    // Nastavenie Adresneho citaca 24LC04 , Adresa (z ktorej citam)/(do ktorej zapisujem)
//	buffer_I2C[1]=<obsah>;			// zapisovane data, byte,-ty
	
	TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); // send start condition 
	// a odovzdanie riadenia "preruseniu od I2C"
	obsluha_Stav_Aut_I2C();

}



unsigned char RD_EEprom(unsigned char adr_RAM)
{ 	
	// nastavenie globalnych premennych

	buffer_I2C[0]=ADR_IC_RD;	// Adr obvodu + rd
	buffer_I2C[1]=adr_RAM;		    // Sem vrati obsah z nastavenej adresy 24LC04

	TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); // send start condition 
	// a odovzdanie riadenia "preruseniu od I2C"
	obsluha_Stav_Aut_I2C();
	return(buffer_I2C[1]);
	
}

// tato funkcia vyuziva globalne premenne 
// buffer_I2C[x]
// Wr_data - tato premenna nadobuda vyznam az pri komunikacii s konkretnou premennou
//           vid. "instrukcny subor" I2C periferie

// implementovany instrukcny subor pre seriovu EEPROM max 256 byte
// S|adr_IO+wr|<AC>|P                -- nastavenie adresneho citaca pamate EEPROM
// {nie je implementova} S|adr_IO+wr|<AC>|data|P           -- zapisanie dat na nastavenu adresu pamate EEPROM
// S|adr_IO+rd|data|P                -- precitanie jedneho bytu z aktualne nastavenej adresy pamate EEPROM
//                                      obsah adresneho citaca sa inkrementne 

void obsluha_Stav_Aut_I2C(void)
{ unsigned char pom_St_Aut=0;
	
	
nav:while ((TWCR & _BV(TWINT)) == 0);  /* wait for transmission */

    {   pom_St_Aut=TWSR & 0xf8;		// precitaj stav 
	    printf(" %02x",pom_St_Aut); 
	 	switch(pom_St_Aut)		
	 	{ case TW_START:// = 0x08 // odvysielany start
		  case TW_REP_START:// = 0x10 // odvysielany repeated start
		                 	TWDR = buffer_I2C[0];// Adr+wr/rd, adresa IO
	  						TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
		  break;
		  
		  case TW_MT_SLA_ACK:	//        0x18   Data byte has been tramsmitted and ACK received
		                 	TWDR = buffer_I2C[1]; // tu konkretne, nastavenie Adreseho citaca pamate.
	  						TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
		  break;

		  case TW_MT_DATA_ACK:	//        0x28   Data byte has been tramsmitted and ACK received
		   					TWCR = _BV(TWINT) | _BV(TWSTO) | _BV(TWEN); /* send stop condition */
							return; //  tento riadok v preruseni vypadne
		  break;

		  case TW_MR_SLA_ACK:	//   0x40  // Data byte has been tramsmitted and NACK received
		   					TWCR = _BV(TWINT) | _BV(TWEN) ; // clear interrupt to start transmission 							
		  break;

		  case TW_MR_DATA_NACK:	// 0x58  // Data byte has been tramsmitted and ACK received
		  				    buffer_I2C[1]= TWDR;	    // Vycitaj jeden byte z  24LC04.  Adresny citac sa posunie
				      		TWCR = _BV(TWINT) | _BV(TWSTO) | _BV(TWEN); // send stop condition 
							return; // tento riadok v preruseni vypadne
		  break;		 

		  default:
		  					TWCR = _BV(TWINT) | _BV(TWSTO) | _BV(TWEN); /* send stop condition */
							return; // tento riadok v preruseni vypadne
		  break;
	 	}
	}
	goto nav; // toto v preruseni vypadne
}




int main(void)
{ 	unsigned char znak;

unsigned int i=0;
unsigned char poc_adresa_EEPROM=0;
	


	inituart();								// inicializacia UARTU                       // inicializacia v 4-bitovom rezime
   	                   

//  sei();                    // Enable ALL interrupts                      

// ini I2C
{  
   
   TWCR =  _BV(TWEN); /* send start condition */
   TWBR = 72; // fi2c= fosc/(16 +2(preddelic=00=> 1)(<TWBR>)) = 100kHz
   TWSR=1;
}


// TODO: to USART 
/* ************************************************************	*/

stdout = &mystdout_Uart;


printf("Nastavenie adresy EEPROM = %02x \n\r",poc_adresa_EEPROM);
WR_EEprom(ADR_IC_WR,poc_adresa_EEPROM);


printf("\n\r\rVypis EEPROM: \n\r");

	// vypisme prvych 10 znakov
    while (i<10) //256)// kapacita pamate 256 znakov, bytov, 
	{ 
		znak = RD_EEprom(ADR_IC_RD); // obsah adresneho citaca EEPROM sa automaticky inkrementuje
		if(znak==0xff)i=256; // vymazane pametove miesto
		{
			printf("   %02d %02x %c\r",i++,znak,znak);
		}
        
	}
	
 for(;;);  // a cakam napr. na  "RESET"
 
}