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 mikroBasic 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

main:
   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 RTC_Read

dim sec, min1, hr, day, mn, year as byte
    tnum, txt as byte[6]

sub procedure Zero_Fill(dim byref value as byte[10])    ' fill text repesentation
    if (value[1] = 0) then
        value[1] = value[0]
        value[0] = 48
        value[2] = 0
    end if
end sub
'-------------- Trims the leading spaces from array given with *pt
sub procedure Rrtrim(dim byref src, dest as byte[10])
  dim i, j as word
    i = 0
    j = 0
    while (src[i] = " ")
      inc(i)
    wend
    while (src[i] <> 0)
      dest[j] = src[i]
      inc(i)
      inc(j)
    wend
    dest[j] = 0
end sub
'--------------------- Reads time and date information from RTC (PCF8583)
sub procedure Read_Time(dim byref sec, min, hr, day, mn as byte)
    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 sub

'-------------------- Formats date and time
sub procedure Transform_Time(dim byref sec, min, hr, day, mn, year as byte)
    sec  =  ((sec and 0xF0) >> 4)*10 + (sec and 0x0F)
    min  =  ((min and 0xF0) >> 4)*10 + (min and 0x0F)
    hr   =  ((hr and 0xF0) >> 4)*10 + (hr and 0x0F)
    year =  (day and 0xC0) >> 6
    day  =  ((day and 0x30) >> 4)*10 + (day and 0x0F)
    mn   =  ((mn and 0x10) >> 4)*10 + (mn and 0x0F)
end sub

'-------------------- Output values to LCD
sub procedure Display_Time( dim sec, min, hr, day, mn, year as byte)

    WordToStr(word(day), tnum)
    Rrtrim(tnum, txt)
    Zero_Fill(txt)
    Lcd_Out(1, 6, txt)

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

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

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

    WordToStr(word(sec), tnum)
    Rrtrim(tnum, txt)
    Zero_Fill(txt)
    Lcd_Out(2,12,txt)
end sub

'------------------ Performs project-wide init
sub procedure Init_Main()
    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 sub
'----------------- Main procedure
main:
  Init_Main()                                     ' perform initialization
  while true
    Read_Time(sec, min1, hr, day, mn)       ' 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
  wend
end.