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:

// *** I2C Protocol Communication *** //
// *** By: Elektronics Garage     *** //
// *** Author: Fayyaz Hussain     *** //

unsigned int Rd_data; // store the Read data in this variable
unsigned int address_N; // address modification variable if needed
void EEPROM_Wr(unsigned int address, unsigned int my_data);// EEPROM Write function
unsigned EEPROM_Rd1(unsigned int address); // EEPROM Read function

void main(){
   unsigned int i,j,a=1;     // variable for loop count
  CMCON = 0x07;           // To turn off comparators
  ADCON1 = 0x06;          // To turn off analog to digital converters
  I2C1_Init(100000);         // satndard speed
  TRISB = 0;                 // Configure PORTB as output
  PORTB = 0;

  while (1){
  for(i=0,a=1;i<8;i++)
                  {EEPROM_Wr(i,a);
                  Delay_ms(100);
                  a = a<<1;
                  } 
                  Delay_ms(200);
  for (j=0;j<8;j++)
                  {Rd_data = EEPROM_Rd1(j);
                  PORTB = Rd_data;
                  Delay_ms(1000);
                  }
  }
  }
  
  void EEPROM_Wr(unsigned int address, unsigned int Wr_data)
  {
           // initialize I2C communication
  I2C1_Start();              // issue I2C start signal
  I2C1_Wr(0xA0);             // send byte via I2C  (device address + W)
  address_N = address>>8;    // saving higher order address to address_N
  I2C1_Wr(address_N);        // send byte (address of EEPROM location)
  I2C1_Wr(address);          // send byte (address of EEPROM location)
  I2C1_Wr(Wr_data);          // send data (data to be written)
  I2C1_Stop();               // issue I2C stop signal
  Delay_ms(15);
  }
  //Delay_100ms();
  unsigned EEPROM_Rd1(unsigned int address)
  {
  I2C1_Start();              // issue I2C start signal
  I2C1_Wr(0xA0);             // send byte via I2C  (device address + W)
  address_N = address>>8;    // saving higher order address to address_N
  I2C1_Wr(address_N);        // send byte (address of EEPROM location)
  I2C1_Wr(address);          // send byte (data address)
  I2C1_Repeated_Start();     // issue I2C signal repeated start
  I2C1_Wr(0xA1);             // send byte (device address + R)
  Rd_data = I2C1_Rd(0u);     // Read the data (NO acknowledge)
  I2C1_Stop();               // issue I2C stop signal
}