TWInet & TWIMaster/TWISlave XMega

  twis_receivedData : array[0..TWIS_RECEIVE_BUFFER_SIZE-1] of byte;
  twis_txData : array[0..TWIS_SEND_BUFFER_SIZE-1] of byte;

program gateway;

Device = xmega128A1U, VCC = 3.3;

Define_Fuses
    Override_Fuses;
    progFuses = true;
    FuseBits1 = [WDPER0, WDPER1, WDPER2];  // watchdog = 2s
    FuseBits4 = [WDLOCK];
    FuseBits5  = [BODLEVEL1, BODLEVEL2, BODACT0]; // 2.8V

Import;

Define
    OSCtype        = extXTAL=8000000, PLLmul=4, prescA=1, prescB=1, prescC=1, faildet;
    StackSize      = 256, iData;
    FrameSize      = 256, iData;


{$DEFINE TWIS_BUFSIZE_128} // rx buffer size for twi
uses xTwiSlaveC;

Implementation
{$IDATA}

const
    TWI_ADDR : byte = $33;

{-------------------------------------------------------------------------------
ControlInterface
-------------------------------------------------------------------------------}
procedure ControlInterface;
var
    rxCount : byte;
    response_size : byte;
begin
    rxCount := TWISdrv_rxComplete();
    if rxCount > 0 then
        // Note: TWI receiver is stopped now, master will receive NACKS until
        //       TWISdrv_StartReceive is called
        twis_txData[0] := twis_receivedData[0];
        response_size := 1; // response command only
        if (response_size > 0) then
            TWISdrv_Transmit(response_size);
        endif;
        TWISdrv_StartReceive(); // enable receiving
    endif;
end;

{-------------------------------------------------------------------------------
Main Program
-------------------------------------------------------------------------------}
begin
    EnableInts($87);
    TWISdrv_Init(TWI_ADDR, nil);
    TWISdrv_StartReceive(); // first start of I2C Slave receiver
    loop
        asm: WDR; // reset watchdog which is enabled by fuses
        ControlInterface;
    endloop;
end.