I2C Communication Using PIC Controller and MikroC for PIC

 

I2C Protocol Communication

I2C Protocol:

I²C (Inter-Integrated Circuit) protocol was invented by Philips Semiconductors in 1980s for on board communication between microcontroller and other peripheral chips. It’s a short distance serial communication that required only two lines (like UART Tx and Rx) for bidirectional data. It’s for low speed peripherals including EEPROMs, digital sensors, I²C LCD and temperature sensors.

Communication lines:

I2C protocol uses 2 lines for communication one is SDA (Serial Data) line and SCL (Serial Clock) line. Any master and any slave can be connected through these two signal lines.

SDA: data transfer on this line from master to slave or salve to master and direction of the data controls through Control signal.

SCL: is clock signal line which is use for synchronization for data transfer.

Connection Diagram:

          Pull up resistors with +Vcc connected because SDA and SCL line are open drain drives.

·        I2C Communication start and stop by master device.

Addressing: After the start condition its necessary to specify the slave address. Because the there are several slave peripherals are connected on the same line. Each slave have a unique address.

After starting the I2C first byte is send to the slave is called control byte because first 7 bits make slave address in which first 4 are fixed and last 3 bits (A2, A1, A0) are programmable and last LSB bit is define to read or write the selected slave.

·        LSB = 0 indicates the Master will write the data

·        LSB = 1 indicates the Master will read the data

When the receiver gets its address, it has to generate the Acknowledge signal.

·        Acknowledge = 0 volt on SDA line (SDA line LOW)

·        No Acknowledge = 5 volt on SDA line

 

Data Transfer Speed:

Mode	Speed
Standard mode	100 Kbps
Fast mode	400 Kbps
High Speed	Up to 3.4 Mbps

 

In short story:

1.      Master initiate (start) I2C

2.      Master send the slave address with Read or write condition

3.      If slave acknowledged

4.      Master will read or write to selected slave 

Circuit Diagram: 

Circuit diagram and Simulation is made in Proteus.

Programming in MikroC:

view source

01	// *** I2C Protocol Communication *** //

02	// *** By: Elektronics Garage     *** //

03	// *** Author: Fayyaz Hussain     *** //

04

05	unsigned int Rd_data; // store the Read data in this variable

06	unsigned int address_N; // address modification variable if needed

07	void EEPROM_Wr(unsigned int address, unsigned int my_data);// EEPROM Write function

08	unsigned EEPROM_Rd1(unsigned int address); // EEPROM Read function

09

10	void main(){

11	unsigned int i,j,a=1;     // variable for loop count

12	CMCON = 0x07;           // To turn off comparators

13	ADCON1 = 0x06;          // To turn off analog to digital converters

14	I2C1_Init(100000);         // satndard speed

15	TRISB = 0;                 // Configure PORTB as output

16	PORTB = 0;

17

18	while (1){

19	for(i=0,a=1;i<8;i++)

20	{EEPROM_Wr(i,a);

21	Delay_ms(100);

22

a = a<<1;

23

}

24	Delay_ms(200);

25	for (j=0;j<8;j++)

26	{Rd_data = EEPROM_Rd1(j);

27	PORTB = Rd_data;

28	Delay_ms(1000);

29

}

30

}

31

}

32

33	void EEPROM_Wr(unsigned int address, unsigned int Wr_data)

34

{

35	// initialize I2C communication

36	I2C1_Start();              // issue I2C start signal

37	I2C1_Wr(0xA0);             // send byte via I2C  (device address + W)

38	address_N = address>>8;    // saving higher order address to address_N

39	I2C1_Wr(address_N);        // send byte (address of EEPROM location)

40	I2C1_Wr(address);          // send byte (address of EEPROM location)

41	I2C1_Wr(Wr_data);          // send data (data to be written)

42	I2C1_Stop();               // issue I2C stop signal

43	Delay_ms(15);

44

}

45	//Delay_100ms();

46	unsigned EEPROM_Rd1(unsigned int address)

47

{

48	I2C1_Start();              // issue I2C start signal

49	I2C1_Wr(0xA0);             // send byte via I2C  (device address + W)

50	address_N = address>>8;    // saving higher order address to address_N

51	I2C1_Wr(address_N);        // send byte (address of EEPROM location)

52	I2C1_Wr(address);          // send byte (data address)

53	I2C1_Repeated_Start();     // issue I2C signal repeated start

54	I2C1_Wr(0xA1);             // send byte (device address + R)

55	Rd_data = I2C1_Rd(0u);     // Read the data (NO acknowledge)

56	I2C1_Stop();               // issue I2C stop signal

57

}