Zbernica i2c: Rozdiel medzi revíziami

Verzia z 15:02, 16. marec 2016

Production history
I²C

Type	Bus
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.^[1]

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^[2]), 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

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

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

Tools

Bus Pirate

Bus Pirate po pripojení sa nainštaluje FTDI serial port driver a OS mu pridelí nejaký port. Cez tento port sa terminálovým programom pripojíme k Bus Piratovi. Parametre portu sú 115 200 bps / 8 / N / 1, no Flow control.

Prvý príkaz je obvykle otáznik, zobrazí sa celé menu.

Postup príkazov pre prácu s i2c zbernicou:

 HiZ> ?

 MENUS
 ? Help
 I Status info
 M Bus mode
 B Terminal speed
 O Data display format
 V Check supply voltages
 F Frequency count on AUX
 G Frequency generator/PWM on AUX
 C AUX pin assignment
 L Bit order
 P Pullup resistors
 = HEX/DEC/BIN converter
 ~ Self test
 # Reset
 $ Bootloader

 SYNTAX
 A/a/@ AUX output toggle H/L/read
 W/w Power supply toggle on/off
 d (D) Measure voltage on ADC probe (continuous)
 [ ({) Start (with read)
 ] or } Stop
 R or r Read byte
 0b Write BIN byte
 0h or 0x Write HEX byte
 0-255 Write DEC byte
 , Delimiter (also space)
 & 1uS delay
 : Repeat (r:2, 0x0a:4, &:20, ^:2, etc.)
 (#) Run macro, (0) for macro list

 RAW BUS OPERATIONS
 /\ Clock H/L
 -/_ Data H/L
 . Read data input pin state
 ^ Clock tick
 ! Read bit

HiZ> M

 1. HiZ
 2. 1-WIRE
 3. UART
 4. I2C
 5. SPI
 6. JTAG
 7. RAW2WIRE
 8. RAW3WIRE
 9. PC KEYBOARD
10. LCD

(1) > 4
Mode selected
Set speed:
 1. ~5KHz
 2. ~50KHz
 3. ~100KHz
 4. ~400KHz
(1) >4
READY

I2C>

Teraz je Pirát pripravený pracovať so zbernicou i2c. Zapneme napájanie a Pull-Up rezistory:

 I2C> w
 POWER SUPPLIES OFF

 I2C> v
 Voltage monitors: 5V: 0.05 | 3.3V: 0.00 | VPULLUP: 0.01 |

 I2C> W
 POWER SUPPLIES ON

 I2C> v
 Voltage monitors: 5V: 6.59 | 3.3V: 3.88 | VPULLUP: 5.00 |

 I2C> P
  1. Pull-ups off
  2. Pull-ups on
 (1) > 2
 Pull-up resistors ON

 I2C>

Preskenujeme zbernicu, co je na nej pripojene:

 I2C> (1)                         <<< macro 1, I2C address search
 Searching 7bit I2C address space.
 Found devices at:
 0xA0(0x50 W) 0xA1(0x50 R)
    
 I2C>

Now we can talk to the chip. I needed something very simple, only to verify that the chip is OK, so I wrote random byte (I chose 0xAA) to the address 0x00 and read it back.

To write a byte to memory we need to enter this [0xA0 0x00 0xAA]

 [         = Start bit
 0xA0 = I2C address of the EEPROM with the WRITE bit
 0x00 = Memory address
 0xAA = Data
 ]          = Stop bit

 I2C> [0xA0 0x00 0xAA]
  I2C START BIT
  WRITE: 0xA0 ACK
  WRITE: 0x00 ACK
  WRITE: 0xAA ACK
  I2C STOP BIT
  
 I2C>

Now we need to set the read pointer to address we want to read. This is accomplished with this command [0xA0 0x00]

 I2C> [0xA0 0x00]
  I2C START BIT
  WRITE: 0xA0 NACK
  WRITE: 0x00 NACK
  I2C STOP BIT
  
 I2C>

And at last we can read the byte stored at the address. [0xA1 r:1] 0xA1 = I2C address of the EEPROM with the READ bit set r:1 = tells the Bus Pirate to read 1 byte

 I2C> [0xA1 rrrrr]    alebo [0xA1 r:5]
  I2C START BIT
  WRITE: 0xA1 ACK
  READ: 0x0B ACK
  READ: 0xA0 ACK
  READ: 0x03 ACK
  READ: 0xAB ACK
  READ: 0x55 NACK
  I2C STOP BIT
  
 I2C>

Toto posledne sa ukazalo ze nefunguje, pretoze random read asi treba spravit takto [0xA0 0x1 0xA [0xA1 r] (opakovany start).

When you're done - na konci:

 I2C> m                            <<<mode menu
 1. HiZ
 ...
 10. LCD
 (1) >                             <<<HiZ is the default
 Mode selected
  
 HiZ>

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"
 
}

[1] I²C Licensing Information

[2] Freescale merger with NXP

[1]

[2]

@@ Riadok 67: / Riadok 67: @@
 * [http://dangerousprototypes.com/2013/05/03/bus-pirate-console/ Bus Pirate Console] ([https://github.com/x893/BusPirateConsole/tree/master/bin/Debug download])
+[[Súbor:BusPirateConnection.png]]
 Bus Pirate po pripojení sa nainštaluje FTDI serial port driver a OS mu pridelí nejaký port.