void PDITarget_SendByte(const uint8_t Byte)
{
#if defined(PDI_VIA_HARDWARE_USART)
    /* Switch to Tx mode if currently in Rx mode */
    if (!(IsSending))
    {
        PORTD  |=  (1 << 3);
        DDRD   |=  (1 << 3);

        UCSR1B |=  (1 << TXEN1);
        UCSR1B &= ~(1 << RXEN1);
        
        IsSending = true;
    }
    
    /* Wait until there is space in the hardware Tx buffer before writing */
    while (!(UCSR1A & (1 << UDRE1)));
    UCSR1A |= (1 << TXC1);
    UDR1    = Byte;
#else ....................

# Place -D or -U options here for C sources
CDEFS  = -DF_CPU=$(F_CPU)UL -DF_CLOCK=$(F_CLOCK)UL -DBOARD=BOARD_$(BOARD) $(LUFA_OPTS)
CDEFS += -DRESET_LINE_PORT=PORTB
CDEFS += -DRESET_LINE_PIN=PINB
CDEFS += -DRESET_LINE_DDR=DDRB
CDEFS += -DRESET_LINE_MASK="(1 << 4)"
CDEFS += -DVTARGET_ADC_CHANNEL=2
CDEFS += -DENABLE_ISP_PROTOCOL
CDEFS += -DENABLE_PDI_PROTOCOL

# MCU name
MCU = at90usb1287

/* Preprocessor Checks and Defines: */
        #if !defined(F_CLOCK)
            #error F_CLOCK is not defined. You must define F_CLOCK to the frequency of the unprescaled input clock in your project makefile.
        #endif
    
        #if (F_CLOCK == 8000000)
            #if (defined(__AVR_AT90USB82__) || defined(__AVR_AT90USB162__) || \
                 defined(__AVR_ATMEGA8U2__) || defined(__AVR_ATMEGA16U2__))
                #define USB_PLL_PSC                0
            #elif (defined(__AVR_ATmega16U4__) || defined(__AVR_ATmega32U4__))
                #define USB_PLL_PSC                0
            #elif (defined(__AVR_AT90USB646__)  || defined(__AVR_AT90USB1286__) || defined(__AVR_ATmega32U6__))
                #define USB_PLL_PSC                ((1 << PLLP1) | (1 << PLLP0))
            #elif (defined(__AVR_AT90USB647__)  || defined(__AVR_AT90USB1287__))
                #define USB_PLL_PSC                ((1 << PLLP1) | (1 << PLLP0))
            #endif
        #elif (F_CLOCK == 16000000)
            #if (defined(__AVR_AT90USB82__) || defined(__AVR_AT90USB162__) || \
                 defined(__AVR_ATMEGA8U2__) || defined(__AVR_ATMEGA16U2__))
                #define USB_PLL_PSC                (1 << PLLP0)
            #elif (defined(__AVR_ATmega16U4__) || defined(__AVR_ATmega32U4__))
                #define USB_PLL_PSC                (1 << PINDIV)
            #elif (defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB647__) || defined(__AVR_ATmega32U6__))
                #define USB_PLL_PSC                ((1 << PLLP2) | (1 << PLLP1))
            #elif (defined(__AVR_AT90USB1286__) || defined(__AVR_AT90USB1287__))
                #define USB_PLL_PSC                ((1 << PLLP2) | (1 << PLLP0))
            #endif
        #endif
        
        #if !defined(USB_PLL_PSC)
            #error No PLL prescale value available for chosen F_CPU value and AVR model.
        #endif