I2C Library

I²C Library

The I²C full master MSSP module is available with a number of PIC MCU models. mikroC PRO for PIC provides library which supports the master I²C mode.

Important :

Some MCUs have multiple I²C modules. In order to use the desired I²C library routine, simply change the number 1 in the prototype with the appropriate module number, i.e. I2C2_Init(100000);

I2C1_Init

Prototype	void I2C1_Init(const unsigned long clock);
Returns	Nothing.
Description	Initializes I²C with desired `clock` (refer to device data sheet for correct values in respect with Fosc). Needs to be called before using other functions of I²C Library. You don’t need to configure ports manually for using the module; library will take care of the initialization.
Requires	Library requires MSSP module. Note : Calculation of the I²C clock value is carried out by the compiler, as it would produce a relatively large code if performed on the library level. Therefore, compiler needs to know the value of the parameter in the compile time. That is why this parameter needs to be a constant, and not a variable.
Example	I2C1_Init(100000);

I2C1_Start

Prototype	unsigned short I2C1_Start(void);
Returns	If there is no error, function returns 0.
Description	Determines if I²C bus is free and issues START signal.
Requires	I²C must be configured before using this function. See I2C1_Init.
Example	I2C1_Start();

I2C1_Repeated_Start

Prototype	void I2C1_Repeated_Start(void);
Returns	Nothing.
Description	Issues repeated START signal.
Requires	I²C must be configured before using this function. See I2C1_Init.
Example	I2C1_Repeated_Start();

I2C1_Is_Idle

Prototype	unsigned short I2C1_Is_Idle(void);
Returns	Returns 1 if I²C bus is free, otherwise returns 0.
Description	Tests if I²C bus is free.
Requires	I²C must be configured before using this function. See I2C1_Init.
Example	if (I2C1_Is_Idle()) {...}

I2C1_Rd

Prototype	unsigned short I2C1_Rd(unsigned short ack);
Returns	Returns one byte from the slave.
Description	Reads one byte from the slave, and sends not acknowledge signal if parameter `ack` is 0, otherwise it sends acknowledge.
Requires	I²C must be configured before using this function. See I2C1_Init. Also, START signal needs to be issued in order to use this function. See I2C1_Start.
Example	Read data and send not acknowledge signal: unsigned short take; ... take = I2C1_Rd(0);

I2C1_Wr

Prototype	unsigned short I2C1_Wr(unsigned short data_);
Returns	Returns 0 if there were no errors.
Description	Sends data byte (parameter `data`) via I²C bus.
Requires	I²C must be configured before using this function. See I2C1_Init. Also, START signal needs to be issued in order to use this function. See I2C1_Start.
Example	I2C1_Write(0xA3);

I2C1_Stop

Prototype	void I2C1_Stop(void);
Returns	Nothing.
Description	Issues STOP signal.
Requires	I²C must be configured before using this function. See I2C1_Init.
Example	I2C1_Stop();

Library Example

This code demonstrates use of I²C library. PIC MCU is connected (SCL, SDA pins) to 24c02 EEPROM. Program sends data to EEPROM (data is written at address 2). Then, we read data via I²C from EEPROM and send its value to PORTB, to check if the cycle was successful (see the figure below how to interface 24c02 to PIC).

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void main(){
  ANSEL  = 0;                // Configure AN pins as digital I/O
  ANSELH = 0;
  PORTB = 0;
  TRISB = 0;                 // Configure PORTB as output

  I2C1_Init(100000);         // initialize I2C communication
  I2C1_Start();              // issue I2C start signal
  I2C1_Wr(0xA2);             // send byte via I2C  (device address + W)
  I2C1_Wr(2);                // send byte (address of EEPROM location)
  I2C1_Wr(0xAA);             // send data (data to be written)
  I2C1_Stop();               // issue I2C stop signal

  Delay_100ms();

  I2C1_Start();              // issue I2C start signal
  I2C1_Wr(0xA2);             // send byte via I2C  (device address + W)
  I2C1_Wr(2);                // send byte (data address)
  I2C1_Repeated_Start();     // issue I2C signal repeated start
  I2C1_Wr(0xA3);             // send byte (device address + R)
  PORTB = I2C1_Rd(0u);       // Read the data (NO acknowledge)
  I2C1_Stop();               // issue I2C stop signal
}

HW Connection

Interfacing 24c02 to PIC via I²C

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