The example shows the initialization, writing, and reading data from the transmit and receive buffer register ofan I2C module, respectively. The example shows the connection of an I2C module to the serial EEPROM memory 24C02. The realization is carried out by using the mikroPascal compiler for dsPIC30F microcontrollers. Fig. 13-11 shows the electrical connection of an I2C module to the EEPROM memory 24C02. The example covers writing to the EEPROM memory, reading data, and data transfer to the PORTF.

Also, an example is presented showing the connection of a device from the dsPIC30F family to the RTC (Real-Time Clock) generator Philips PCF8583P. The example covers writing to and reading from the RTC generator by using an I2C standard interface. Date and time are printed at LCD.

program RTCWrite;

begin
   ADPCFG := 0xFFFF;
   I2C_Init(10000);         // initialize full master mode
   I2C_Start();             // issue start signal
   I2C_Write(0xA0);         // address PCF8583
   I2C_Write(0);            // start from word at address 0 (configuration word)
   I2C_Write(0x80);         // write $80 to config. (pause counter...)
   I2C_Write(0);            // write 0 to cents word
   I2C_Write(0);            // write 0 to seconds word
   I2C_Write(0x30);         // write $30 to minutes word
   I2C_Write(0x11);         // write $11 to hours word
   I2C_Write(0x24);         // write $24 to year/date word
   I2C_Write(0x08);         // write $08 to weekday/month
   I2C_Stop();              // issue stop signal

   I2C_Start();             // issue start signal
   I2C_Write(0xA0);         // address PCF8530
   I2C_Write(0);            // start from word at address 0
   I2C_Write(0);            // write 0 to config word (enable counting)
   I2C_Stop();              // issue stop signal
end.

program RTCRead;
 
var sec, min1, hr, day, mn, year : byte;
    tnum, txt : array[6] of byte;

procedure Zero_Fill(var value : array[10] of byte);    // fill text repesentation
  begin
    if (value[1] = 0) then
      begin           //      with leading zero
        value[1] := value[0];
        value[0] := 48;
        value[2] := 0;
      end;
  end;
//-------------- Trims the leading spaces from array given with *pt
procedure rtrim(var src, dest : array[10] of byte);
  var i, j : word;
  begin
    i := 0;
    j := 0;
    while (src[i] = ' ') do
      inc(i);
    while (src[i] <> 0) do
      begin
        dest[j] := src[i];
        inc(i);
        inc(j);
      end;
    dest[j] := 0;
  end;
//--------------------- Reads time and date information from RTC (PCF8583)
procedure Read_Time(var sec, min, hr, day, mn, year : byte);
  begin
    I2C_Start();
    I2C_Write(0xA0);
    I2C_Write(2);
    I2c_Restart();
    I2C_Write(0xA1);
    sec := I2c_Read(0);
    min := I2c_Read(0);
    hr  := I2c_Read(0);
    day := I2c_Read(0);
    mn  := I2c_Read(1);
    I2C_Stop();

  end;

//-------------------- Formats date and time
procedure Transform_Time(var sec, min, hr, day, mn, year : byte);
  begin
    sec  :=  ((sec and 0xF0) shr 4)*10 + (sec and 0x0F);
    min  :=  ((min and 0xF0) shr 4)*10 + (min and 0x0F);
    hr   :=  ((hr and 0xF0) shr 4)*10 + (hr and 0x0F);
    year :=  (day and 0xC0) shr 6;
    day  :=  ((day and 0x30) shr 4)*10 + (day and 0x0F);
    mn   :=  ((mn and 0x10) shr 4)*10 + (mn and 0x0F);
  end;

//-------------------- Output values to LCD
procedure Display_Time( sec, min, hr, day, mn, year : byte);
  begin
    WordToStr(word(day), tnum);
    rtrim(tnum, txt);
    Zero_Fill(txt);
    Lcd_Out(1, 6, txt);

    WordToStr(word(mn), tnum);
    rtrim(tnum, txt);
    Zero_Fill(txt);
    Lcd_Out(1,9,txt);
    Lcd_Chr(1,15,52+year);

    WordToStr(word(hr), tnum);
    rtrim(tnum, txt);
    Zero_Fill(txt);
    Lcd_Out(2,6,txt);

    WordToStr(word(min), tnum);
    rtrim(tnum, txt);
    Zero_Fill(txt);
    Lcd_Out(2,9,txt);

    WordToStr(word(sec), tnum);
    rtrim(tnum, txt);
    Zero_Fill(txt);
    Lcd_Out(2,12,txt);
  end;

//------------------ Performs project-wide init
procedure Init_Main();
  begin
    ADPCFG := 0xFFFF;
    TRISD  := 0;                // designate portd as output
    Lcd_Init_EasyDsPIC4();
    I2C_Init(100000);           // initialize I2C
    txt := 'Date:';             // prepare and output static text on LCD
    Lcd_Out(1,1,txt);
    Lcd_Chr(1,8,':');
    Lcd_Chr(1,11,':');
    txt := 'Time:';
    Lcd_Out(2,1,txt);
    Lcd_Chr(2,8,':');
    Lcd_Chr(2,11,':');
    txt := '200';
    Lcd_Out(1,12,txt);
    Lcd_Cmd(LCD_CURSOR_OFF);   // cursor off
  end;
//----------------- Main procedure
begin
  Init_Main();                                       // perform initialization
  while true do
    begin
      Read_Time(sec, min1, hr, day, mn, year);       // read time from RTC(PCF8583)
      Transform_Time(sec, min1, hr, day, mn, year);  // format date and time
      Display_Time(sec, min1, hr, day, mn, year);    // prepare and display on LCD
      Delay_ms(1000);                                // wait 1s
    end;
end.