Software I2C Library

Software I²C Library

The mikroC PRO for ARM provides routines for implementing Software I²C communication. These routines are hardware independent and can be used with any MCU. The Software I²C library enables you to use MCU as Master in I²C communication. Multi-master mode is not supported.

Important :

This library implements time-based activities, so interrupts need to be disabled when using Software I²C.
All I²C Library functions are blocking-call functions (they are waiting for I²C clock line to become logical one).
The pins used for the Software I²C communication should be connected to the pull-up resistors. Turning off the LEDs connected to these pins may also be required.
Every Software I²C library routine has its own counterpart in Hardware I²C library, except I2C_Repeated_Start. Soft_I2C_Start is used instead of I2C_Repeated_Start.
Working clock frequency of the Software I²C is 20kHz.

Stellaris

The following variables must be defined in all projects using Software I²C Library:	Description :	Example :
`extern sbit Soft_I2C_Scl;`	Soft I²C Clock line.	`sbit Soft_I2C_Scl at GPIO_PORTD_DATA3_bit;`
`extern sbit Soft_I2C_Sda;`	Soft I²C Data line.	`sbit Soft_I2C_Sda at GPIO_PORTD_DATA4_bit;`
`extern sbit Soft_I2C_Scl_Direction;`	Direction of the Soft I²C Clock pin.	`sbit Soft_I2C_Scl_Direction at GPIO_PORTD_DIR3_bit;`
`extern sbit Soft_I2C_Sda_Direction;`	Direction of the Soft I²C Data pin.	`sbit Soft_I2C_Sda_Direction at GPIO_PORTD_DIR4_bit;`

STM32

The following variables must be defined in all projects using Software I²C Library:	Description :	Example :
`extern sbit Soft_I2C_Scl_Output;`	Soft I²C Clock Output line.	`sbit Soft_I2C_Scl_Output at GPIOD_ODR.B3;`
`extern sbit Soft_I2C_Scl_Input;`	Soft I²C Clock Input line.	`sbit Soft_I2C_Scl_Input at GPIOD_IDR.B3;`
`extern sbit Soft_I2C_Sda_Output;`	Soft I²C Data Output line.	`sbit Soft_I2C_Sda_Output at GPIOD_ODR.B4;`
`extern sbit Soft_I2C_Sda_Input;`	Soft I²C Data Input line.	`sbit Soft_I2C_Sda_Input at GPIOD_IDR.B3;`

Soft_I2C_Init

Prototype	void Soft_I2C_Init();
Description	Configures the software I²C module.
Parameters	None.
Returns	Nothing.
Requires	External dependencies of the library from the top of the page must be defined before using this function.
Example	Stellaris // Software I2C connections sbit Soft_I2C_Scl at GPIO_PORTD_DATA3_bit; sbit Soft_I2C_Sda at GPIO_PORTD_DATA4_bit; sbit Soft_I2C_Scl_Direction at GPIO_PORTD_DIR3_bit; sbit Soft_I2C_Sda_Direction at GPIO_PORTD_DIR4_bit; // End Software I2C connections ... Soft_I2C_Init(); STM32 // Software I2C connections sbit Soft_I2C_Scl_Output at GPIOD_ODR.B3; sbit Soft_I2C_Scl_Input at GPIOD_IDR.B3; sbit Soft_I2C_Sda_Output at GPIOD_ODR.B4; sbit Soft_I2C_Sda_Input at GPIOD_IDR.B4; // End Software I2C connections ... Soft_I2C_Init();
Notes	None.

Soft_I2C_Start

Prototype	void Soft_I2C_Start();
Description	Determines if the I²C bus is free and issues START signal.
Parameters	None.
Returns	Nothing.
Requires	Software I²C must be configured before using this function. See Soft_I2C_Init routine.
Example	// Issue START signal Soft_I2C_Start();
Notes	None.

Soft_I2C_Read

Prototype	unsigned short Soft_I2C_Read(unsigned int ack);
Description	Reads one byte from the slave.
Parameters	`ack:` acknowledge signal parameter. If the `ack==0` not acknowledge signal will be sent after reading, otherwise the acknowledge signal will be sent.
Returns	One byte from the Slave.
Requires	Soft I²C must be configured before using this function. See Soft_I2C_Init routine. Also, START signal needs to be issued in order to use this function. See Soft_I2C_Start routine.
Example	unsigned short take; ... // Read data and send the not_acknowledge signal take = Soft_I2C_Read(0);
Notes	None.

Soft_I2C_Write

Prototype	unsigned short Soft_I2C_Write(unsigned short data_);
Description	Sends data byte via the I²C bus.
Parameters	`data_:` data to be sent
Returns	`0` if there were no errors. `1` if write collision was detected on the I²C bus.
Requires	Soft I²C must be configured before using this function. See Soft_I2C_Init routine. Also, START signal needs to be issued in order to use this function. See Soft_I2C_Start routine.
Example	unsigned short data_, error; ... error = Soft_I2C_Write(data_); error = Soft_I2C_Write(0xA3);
Notes	None.

Soft_I2C_Stop

Prototype	void Soft_I2C_Stop();
Description	Issues STOP signal.
Parameters	None.
Returns	Nothing.
Requires	Soft I²C must be configured before using this function. See Soft_I2C_Init routine.
Example	// Issue STOP signal Soft_I2C_Stop();
Notes	None.

Soft_I2C_Break

Prototype	void Soft_I2C_Break();
Description	All Software I²C Library functions can block the program flow (see note at the top of this page). Calling this routine from interrupt will unblock the program execution. This mechanism is similar to WDT.
Parameters	None.
Returns	Nothing.
Requires	Nothing.
Example
Notes	Interrupts should be disabled before using Software I²C routines again (see note at the top of this page).

Library Example

The example demonstrates use of the Software I²C Library. The ARM MCU is connected (SCL, SDA pins) to PCF8583 RTC (real-time clock). Program sends date/time to RTC.

Stellaris

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char seconds, minutes, hours, day, month, year;    // Global date/time variables

// Software I2C connections
sbit Soft_I2C_Scl           at GPIO_PORTD_DATA3_bit;
sbit Soft_I2C_Sda           at GPIO_PORTD_DATA4_bit;
sbit Soft_I2C_Scl_Direction at GPIO_PORTD_DIR3_bit;
sbit Soft_I2C_Sda_Direction at GPIO_PORTD_DIR4_bit;
// End Software I2C connections

// LCD module connections
sbit LCD_RS at GPIO_PORTA_DATA2_bit;
sbit LCD_EN at GPIO_PORTA_DATA3_bit;
sbit LCD_D4 at GPIO_PORTA_DATA4_bit;
sbit LCD_D5 at GPIO_PORTA_DATA5_bit;
sbit LCD_D6 at GPIO_PORTA_DATA6_bit;
sbit LCD_D7 at GPIO_PORTA_DATA7_bit;

sbit LCD_RS_Direction at GPIO_PORTA_DIR2_bit;
sbit LCD_EN_Direction at GPIO_PORTA_DIR3_bit;
sbit LCD_D4_Direction at GPIO_PORTA_DIR4_bit;
sbit LCD_D5_Direction at GPIO_PORTA_DIR5_bit;
sbit LCD_D6_Direction at GPIO_PORTA_DIR6_bit;
sbit LCD_D7_Direction at GPIO_PORTA_DIR7_bit;
// End LCD module connections

//--------------------- Reads time and date information from RTC (PCF8583)
void Read_Time() {

  Soft_I2C_Start();               // Issue start signal
  Soft_I2C_Write(0xA0);           // Address PCF8583, see PCF8583 datasheet
  Soft_I2C_Write(2);              // Start from address 2
  Soft_I2C_Start();               // Issue repeated start signal
  Soft_I2C_Write(0xA1);           // Address PCF8583 for reading R/W=1

  seconds = Soft_I2C_Read(1);     // Read seconds byte
  minutes = Soft_I2C_Read(1);     // Read minutes byte
  hours = Soft_I2C_Read(1);       // Read hours byte
  day = Soft_I2C_Read(1);         // Read year/day byte
  month = Soft_I2C_Read(0);       // Read weekday/month byte
  Soft_I2C_Stop();                // Issue stop signal

}

//-------------------- Formats date and time
void Transform_Time() {
  seconds  =  ((seconds & 0xF0) >> 4)*10 + (seconds & 0x0F);  // Transform seconds
  minutes  =  ((minutes & 0xF0) >> 4)*10 + (minutes & 0x0F);  // Transform months
  hours    =  ((hours & 0xF0)  >> 4)*10  + (hours & 0x0F);    // Transform hours
  year     =   (day & 0xC0) >> 6;                             // Transform year
  day      =  ((day & 0x30) >> 4)*10    + (day & 0x0F);       // Transform day
  month    =  ((month & 0x10)  >> 4)*10 + (month & 0x0F);     // Transform month
}

//-------------------- Output values to LCD
void Display_Time() {

   Lcd_Chr(1, 6, (day / 10)   + 48);    // Print tens digit of day variable
   Lcd_Chr(1, 7, (day % 10)   + 48);    // Print oness digit of day variable
   Lcd_Chr(1, 9, (month / 10) + 48);
   Lcd_Chr(1,10, (month % 10) + 48);
   Lcd_Chr(1,15,  year        + 49);    // Print year vaiable + 1 (start from year 2011)

   Lcd_Chr(2, 6, (hours / 10)   + 48);
   Lcd_Chr(2, 7, (hours % 10)   + 48);
   Lcd_Chr(2, 9, (minutes / 10) + 48);
   Lcd_Chr(2,10, (minutes % 10) + 48);
   Lcd_Chr(2,12, (seconds / 10) + 48);
   Lcd_Chr(2,13, (seconds % 10) + 48);
}

//------------------ Performs project-wide init
void Init_Main() {
  Soft_I2C_Init();           // Initialize Soft I2C communication
  Lcd_Init();                // Initialize LCD
  Lcd_Cmd(_LCD_CLEAR);       // Clear LCD display
  Lcd_Cmd(_LCD_CURSOR_OFF);  // Turn cursor off

  Lcd_Out(1,1,"Date:");      // Prepare and output static text on LCD
  Lcd_Chr(1,8,':');
  Lcd_Chr(1,11,':');
  Lcd_Out(2,1,"Time:");
  Lcd_Chr(2,8,':');
  Lcd_Chr(2,11,':');
  Lcd_Out(1,12,"201");

}

//----------------- Main procedure
void main() {

  Delay_ms(100);

  Init_Main();               // Perform initialization

  while (1) {                // Endless loop
    Read_Time();             // Read time from RTC(PCF8583)
    Transform_Time();        // Format date and time
    Display_Time();          // Prepare and display on LCD

    Delay_ms(1000);          // Wait 1 second
  }
}

STM32

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char seconds, minutes, hours, day, month, year;    // Global date/time variables

// Software I2C connections
sbit Soft_I2C_Scl_Output    at GPIOD_ODR.B3;
sbit Soft_I2C_Scl_Input     at GPIOD_IDR.B3;
sbit Soft_I2C_Sda_Output    at GPIOD_ODR.B4;
sbit Soft_I2C_Sda_Input     at GPIOD_IDR.B4;
// End Software I2C connections

// LCD module connections
sbit LCD_RS at GPIOD_ODR.B10;
sbit LCD_EN at GPIOD_ODR.B11;
sbit LCD_D4 at GPIOD_ODR.B12;
sbit LCD_D5 at GPIOD_ODR.B13;
sbit LCD_D6 at GPIOD_ODR.B14;
sbit LCD_D7 at GPIOD_ODR.B15;
// End LCD module connections


// End LCD module connections

//--------------------- Reads time and date information from RTC (PCF8583)
void Read_Time() {

  Soft_I2C_Start();               // Issue start signal
  Soft_I2C_Write(0xA0);           // Address PCF8583, see PCF8583 datasheet
  Soft_I2C_Write(2);              // Start from address 2
  Soft_I2C_Start();               // Issue repeated start signal
  Soft_I2C_Write(0xA1);           // Address PCF8583 for reading R/W=1

  seconds = Soft_I2C_Read(1);     // Read seconds byte
  minutes = Soft_I2C_Read(1);     // Read minutes byte
  hours = Soft_I2C_Read(1);       // Read hours byte
  day = Soft_I2C_Read(1);         // Read year/day byte
  month = Soft_I2C_Read(0);       // Read weekday/month byte
  Soft_I2C_Stop();                // Issue stop signal

}

//-------------------- Formats date and time
void Transform_Time() {
  seconds  =  ((seconds & 0xF0) >> 4)*10 + (seconds & 0x0F);  // Transform seconds
  minutes  =  ((minutes & 0xF0) >> 4)*10 + (minutes & 0x0F);  // Transform months
  hours    =  ((hours & 0xF0)  >> 4)*10  + (hours & 0x0F);    // Transform hours
  year     =   (day & 0xC0) >> 6;                             // Transform year
  day      =  ((day & 0x30) >> 4)*10    + (day & 0x0F);       // Transform day
  month    =  ((month & 0x10)  >> 4)*10 + (month & 0x0F);     // Transform month
}

//-------------------- Output values to LCD
void Display_Time() {

   Lcd_Chr(1, 6, (day / 10)   + 48);    // Print tens digit of day variable
   Lcd_Chr(1, 7, (day % 10)   + 48);    // Print oness digit of day variable
   Lcd_Chr(1, 9, (month / 10) + 48);
   Lcd_Chr(1,10, (month % 10) + 48);
   Lcd_Chr(1,15,  year        + 49);    // Print year vaiable + 1 (start from year 2011)

   Lcd_Chr(2, 6, (hours / 10)   + 48);
   Lcd_Chr(2, 7, (hours % 10)   + 48);
   Lcd_Chr(2, 9, (minutes / 10) + 48);
   Lcd_Chr(2,10, (minutes % 10) + 48);
   Lcd_Chr(2,12, (seconds / 10) + 48);
   Lcd_Chr(2,13, (seconds % 10) + 48);
}

//------------------ Performs project-wide init
void Init_Main() {
  Soft_I2C_Init();           // Initialize Soft I2C communication
  Lcd_Init();                // Initialize LCD
  Lcd_Cmd(_LCD_CLEAR);       // Clear LCD display
  Lcd_Cmd(_LCD_CURSOR_OFF);  // Turn cursor off

  Lcd_Out(1,1,"Date:");      // Prepare and output static text on LCD
  Lcd_Chr(1,8,':');
  Lcd_Chr(1,11,':');
  Lcd_Out(2,1,"Time:");
  Lcd_Chr(2,8,':');
  Lcd_Chr(2,11,':');
  Lcd_Out(1,12,"201");

}

//----------------- Main procedure
void main() {

  Delay_ms(100);

  Init_Main();               // Perform initialization

  while (1) {                // Endless loop
    Read_Time();             // Read time from RTC(PCF8583)
    Transform_Time();        // Format date and time
    Display_Time();          // Prepare and display on LCD

    Delay_ms(1000);          // Wait 1 second
  }
}

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