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// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// + Copyright (c) Holger Buss, Ingo Busker
// + Nur für den privaten Gebrauch
// + www.MikroKopter.com
// + porting the sources to other systems or using the software on other systems (except hardware from www.mikrokopter.de) is not allowed
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// + Es gilt für das gesamte Projekt (Hardware, Software, Binärfiles, Sourcecode und Dokumentation),
// + dass eine Nutzung (auch auszugsweise) nur für den privaten (nicht-kommerziellen) Gebrauch zulässig ist.
// + Sollten direkte oder indirekte kommerzielle Absichten verfolgt werden, ist mit uns (info@mikrokopter.de) Kontakt
// + bzgl. der Nutzungsbedingungen aufzunehmen.
// + Eine kommerzielle Nutzung ist z.B.Verkauf von MikroKoptern, Bestückung und Verkauf von Platinen oder Bausätzen,
// + Verkauf von Luftbildaufnahmen, usw.
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// + Werden Teile des Quellcodes (mit oder ohne Modifikation) weiterverwendet oder veröffentlicht,
// + unterliegen sie auch diesen Nutzungsbedingungen und diese Nutzungsbedingungen incl. Copyright müssen dann beiliegen
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// + Sollte die Software (auch auszugesweise) oder sonstige Informationen des MikroKopter-Projekts
// + auf anderen Webseiten oder sonstigen Medien veröffentlicht werden, muss unsere Webseite "http://www.mikrokopter.de"
// + eindeutig als Ursprung verlinkt werden
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// + Keine Gewähr auf Fehlerfreiheit, Vollständigkeit oder Funktion
// + Benutzung auf eigene Gefahr
// + Wir übernehmen keinerlei Haftung für direkte oder indirekte Personen- oder Sachschäden
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// + Die Portierung der Software (oder Teile davon) auf andere Systeme (ausser der Hardware von www.mikrokopter.de) ist nur
// + mit unserer Zustimmung zulässig
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// + Die Funktion printf_P() unterliegt ihrer eigenen Lizenz und ist hiervon nicht betroffen
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// + Redistributions of source code (with or without modifications) must retain the above copyright notice,
// + this list of conditions and the following disclaimer.
// +   * Neither the name of the copyright holders nor the names of contributors may be used to endorse or promote products derived
// +     from this software without specific prior written permission.
// +   * The use of this project (hardware, software, binary files, sources and documentation) is only permittet
// +     for non-commercial use (directly or indirectly)
// +     Commercial use (for excample: selling of MikroKopters, selling of PCBs, assembly, ...) is only permitted
// +     with our written permission
// +   * If sources or documentations are redistributet on other webpages, out webpage (http://www.MikroKopter.de) must be
// +     clearly linked as origin
// +   * porting to systems other than hardware from www.mikrokopter.de is not allowed
// +  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// +  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// +  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// +  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// +  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// +  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// +  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// +  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN// +  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// +  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// +  POSSIBILITY OF SUCH DAMAGE.
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#include <avr/io.h>
#include <avr/interrupt.h>
#include <string.h>
#include <stdlib.h>
#include "main.h"
#include "spi.h"
#include "fc.h"
#include "rc.h"
#include "eeprom.h"
#include "uart0.h"
#include "timer0.h"
#include "analog.h"


//-----------------------------------------
#define DDR_SPI DDRB
#define DD_SS   PB4
#define DD_SCK  PB7
#define DD_MOSI PB5
#define DD_MISO PB6

// for compatibility reasons gcc3.x <-> gcc4.x
#ifndef SPCR
#define SPCR   SPCR0
#endif
#ifndef SPIE
#define SPIE   SPIE0
#endif
#ifndef SPE
#define SPE    SPE0
#endif
#ifndef DORD
#define DORD   DORD0
#endif
#ifndef MSTR
#define MSTR   MSTR0
#endif
#ifndef CPOL
#define CPOL   CPOL0
#endif
#ifndef CPHA
#define CPHA   CPHA0
#endif
#ifndef SPR1
#define SPR1   SPR01
#endif
#ifndef SPR0
#define SPR0   SPR00
#endif

#ifndef SPDR
#define SPDR   SPDR0
#endif

#ifndef SPSR
#define SPSR   SPSR0
#endif
#ifndef SPIF
#define SPIF   SPIF0
#endif
#ifndef WCOL
#define WCOL   WCOL0
#endif
#ifndef SPI2X
#define SPI2X  SPI2X0
#endif
// -------------------------

#define SLAVE_SELECT_DDR_PORT   DDRC
#define SLAVE_SELECT_PORT       PORTC
#define SPI_SLAVE_SELECT        PC5


#define SPI_TXSYNCBYTE1 0xAA
#define SPI_TXSYNCBYTE2 0x83
#define SPI_RXSYNCBYTE1 0x81
#define SPI_RXSYNCBYTE2 0x55

typedef enum
{
        SPI_SYNC1,
        SPI_SYNC2,
        SPI_DATA
} SPI_RXState_t;


// data exchange packets to and From NaviCtrl
ToNaviCtrl_t                    ToNaviCtrl;
FromNaviCtrl_t                  FromNaviCtrl;

SPI_VersionInfo_t SPI_VersionInfo;

// rx packet buffer
#define SPI_RXBUFFER_LEN sizeof(FromNaviCtrl)
uint8_t SPI_RxBuffer[SPI_RXBUFFER_LEN];
uint8_t SPI_RxBufferIndex = 0;
uint8_t SPI_RxBuffer_Request = 0;

// tx packet buffer
#define SPI_TXBUFFER_LEN sizeof(ToNaviCtrl)
uint8_t *SPI_TxBuffer;
uint8_t SPI_TxBufferIndex = 0;

uint8_t SPITransferCompleted, SPI_ChkSum;
uint8_t SPI_RxDataValid = 0;
uint8_t NCDataOkay = 0;
uint8_t NCSerialDataOkay = 0;
int8_t  NCGpsZ = 0;

uint8_t SPI_CommandSequence[] = { SPI_CMD_USER, SPI_CMD_STICK, SPI_CMD_PARAMETER1, SPI_CMD_STICK, SPI_CMD_MISC, SPI_CMD_VERSION, SPI_CMD_SERVOS};
uint8_t SPI_CommandCounter = 0;

/*********************************************/
/*  Initialize SPI interface to NaviCtrl     */
/*********************************************/
void SPI_MasterInit(void)
{
        DDR_SPI |= (1<<DD_MOSI)|(1<<DD_SCK);    // Set MOSI and SCK output, all others input
        SLAVE_SELECT_DDR_PORT |= (1 << SPI_SLAVE_SELECT); // set Slave select port as output port

        SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR1)|(0<<SPR0)|(0<<SPIE);   // Enable SPI, Master, set clock rate fck/64
        SPSR = 0;//(1<<SPI2X);

        SLAVE_SELECT_PORT |=  (1 << SPI_SLAVE_SELECT); // Deselect Slave

        SPI_TxBuffer = (uint8_t *) &ToNaviCtrl; // set pointer to tx-buffer
        SPITransferCompleted = 1;
        // initialize data packet to NaviControl
        ToNaviCtrl.Sync1 = SPI_TXSYNCBYTE1;
        ToNaviCtrl.Sync2 = SPI_TXSYNCBYTE2;

        ToNaviCtrl.Command = SPI_CMD_USER;
        ToNaviCtrl.IntegralNick = 0;
        ToNaviCtrl.IntegralRoll = 0;
        NCSerialDataOkay = 0;
        NCDataOkay = 0;

        SPI_RxDataValid = 0;

        SPI_VersionInfo.Major = VERSION_MAJOR;
        SPI_VersionInfo.Minor = VERSION_MINOR;
        SPI_VersionInfo.Patch = VERSION_PATCH;
        SPI_VersionInfo.Compatible = NC_SPI_COMPATIBLE;
}


/**********************************************************/
/*  Update Data transferd by the SPI from/to NaviCtrl     */
/**********************************************************/
void UpdateSPI_Buffer(void)
{
        int16_t tmp;

        // update content of packet to NaviCtrl
        ToNaviCtrl.IntegralNick = (int16_t)((10 * IntegralGyroNick) / GYRO_DEG_FACTOR); // convert to multiple of 0.1°
        ToNaviCtrl.IntegralRoll = (int16_t)((10 * IntegralGyroRoll) / GYRO_DEG_FACTOR); // convert to multiple of 0.1°
        ToNaviCtrl.GyroHeading  = (int16_t)((10 * YawGyroHeading)   / GYRO_DEG_FACTOR); // convert to multiple of 0.1°
        ToNaviCtrl.GyroNick = GyroNick;
        ToNaviCtrl.GyroRoll = GyroRoll;
        ToNaviCtrl.GyroYaw =  GyroYaw;
        ToNaviCtrl.AccNick =  ((int16_t) 10 * ACC_AMPLIFY * (NaviAccNick / NaviCntAcc)) / ACC_DEG_FACTOR; // convert to multiple of 0.1°
        ToNaviCtrl.AccRoll =  ((int16_t) 10 * ACC_AMPLIFY * (NaviAccRoll / NaviCntAcc)) / ACC_DEG_FACTOR; // convert to multiple of 0.1°
        NaviCntAcc = 0; NaviAccNick = 0; NaviAccRoll = 0;

        switch(ToNaviCtrl.Command)
        {
                case SPI_CMD_USER:
                        ToNaviCtrl.Param.Byte[0] = FCParam.UserParam1;
                        ToNaviCtrl.Param.Byte[1] = FCParam.UserParam2;
                        ToNaviCtrl.Param.Byte[2] = FCParam.UserParam3;
                        ToNaviCtrl.Param.Byte[3] = FCParam.UserParam4;
                        ToNaviCtrl.Param.Byte[4] = FCParam.UserParam5;
                        ToNaviCtrl.Param.Byte[5] = FCParam.UserParam6;
                        ToNaviCtrl.Param.Byte[6] = FCParam.UserParam7;
                        ToNaviCtrl.Param.Byte[7] = FCParam.UserParam8;
                        ToNaviCtrl.Param.Byte[8] = MKFlags;
                        MKFlags &= ~(MKFLAG_CALIBRATE | MKFLAG_START); // calibrate and start are temporal states that are cleared immediately after transmitting
                        ToNaviCtrl.Param.Byte[9] = (uint8_t)UBat;
                        ToNaviCtrl.Param.Byte[10] = LowVoltageWarning;
                        ToNaviCtrl.Param.Byte[11] = GetActiveParamSet();
                        break;

                case SPI_CMD_PARAMETER1:
                        ToNaviCtrl.Param.Byte[0] = ParamSet.NaviGpsModeControl;     // Parameters for the Naviboard
                        ToNaviCtrl.Param.Byte[1] = ParamSet.NaviGpsGain;
                        ToNaviCtrl.Param.Byte[2] = ParamSet.NaviGpsP;
                        ToNaviCtrl.Param.Byte[3] = ParamSet.NaviGpsI;
                        ToNaviCtrl.Param.Byte[4] = ParamSet.NaviGpsD;
                        ToNaviCtrl.Param.Byte[5] = ParamSet.NaviGpsACC;
                        ToNaviCtrl.Param.Byte[6] = ParamSet.NaviGpsMinSat;
                        ToNaviCtrl.Param.Byte[7] = ParamSet.NaviStickThreshold;
                        ToNaviCtrl.Param.Byte[8] = ParamSet.NaviOperatingRadius;
                        ToNaviCtrl.Param.Byte[9] = ParamSet.NaviWindCorrection;
            ToNaviCtrl.Param.Byte[10] = ParamSet.NaviSpeedCompensation;
            ToNaviCtrl.Param.Byte[11] = ParamSet.NaviAngleLimitation;
                        break;


                case SPI_CMD_STICK:
                        cli();
                        tmp = PPM_in[ParamSet.ChannelAssignment[CH_GAS]];  if(tmp > 127) tmp = 127; else if(tmp < -128) tmp = -128;
                        ToNaviCtrl.Param.Byte[0] = (int8_t) tmp;
                        tmp = PPM_in[ParamSet.ChannelAssignment[CH_YAW]]; if(tmp > 127) tmp = 127; else if(tmp < -128) tmp = -128;
                        ToNaviCtrl.Param.Byte[1] = (int8_t) tmp;
                        tmp = PPM_in[ParamSet.ChannelAssignment[CH_ROLL]]; if(tmp > 127) tmp = 127; else if(tmp < -128) tmp = -128;
                        ToNaviCtrl.Param.Byte[2] = (int8_t) tmp;
                        tmp = PPM_in[ParamSet.ChannelAssignment[CH_NICK]]; if(tmp > 127) tmp = 127; else if(tmp < -128) tmp = -128;
                        ToNaviCtrl.Param.Byte[3] = (int8_t) tmp;
                        sei();
                        ToNaviCtrl.Param.Byte[4] = (uint8_t) Poti1;
                        ToNaviCtrl.Param.Byte[5] = (uint8_t) Poti2;
                        ToNaviCtrl.Param.Byte[6] = (uint8_t) Poti3;
                        ToNaviCtrl.Param.Byte[7] = (uint8_t) Poti4;
                        ToNaviCtrl.Param.Byte[8] = (uint8_t) RC_Quality;
                        ToNaviCtrl.Param.Byte[9] = (uint8_t) RC_RSSI;
                        ToNaviCtrl.Param.Byte[10] = DebugOut.Analog[7] / 4; // gasmixfraction
                        break;

                case SPI_CMD_MISC:
                        ToNaviCtrl.Param.Byte[0] = CompassCalState;
                        if(CompassCalState > 4)
                        { // jump from 5 to 0
                                CompassCalState  = 0;
                        }
                        ToNaviCtrl.Param.Byte[1] = ParamSet.NaviPHLoginTime;
                        ToNaviCtrl.Param.Int[1]  = (int16_t)(ReadingHeight/5); // at address of Byte 2 and 3
                        ToNaviCtrl.Param.Int[2]  = (int16_t)(SetPointHeight/5);// at address of Byte 4 and 5
                        ToNaviCtrl.Param.Byte[6] = ParamSet.NaviGpsPLimit;
                        ToNaviCtrl.Param.Byte[7] = ParamSet.NaviGpsILimit;
                        ToNaviCtrl.Param.Byte[8] = ParamSet.NaviGpsDLimit;
                        break;

                case SPI_CMD_VERSION:
                        ToNaviCtrl.Param.Byte[0] = SPI_VersionInfo.Major;
                        ToNaviCtrl.Param.Byte[1] = SPI_VersionInfo.Minor;
                        ToNaviCtrl.Param.Byte[2] = SPI_VersionInfo.Patch;
                        ToNaviCtrl.Param.Byte[3] = SPI_VersionInfo.Compatible;
                        ToNaviCtrl.Param.Byte[4] = BoardRelease;
                        break;

                case SPI_CMD_SERVOS:
                        ToNaviCtrl.Param.Byte[0] = ParamSet.ServoRefresh;     // Parameters for the Servo Control
                        ToNaviCtrl.Param.Byte[1] = ParamSet.ServoCompInvert;
                        ToNaviCtrl.Param.Byte[2] = FCParam.ServoNickControl;
                        ToNaviCtrl.Param.Byte[3] = ParamSet.ServoNickComp;
                        ToNaviCtrl.Param.Byte[4] = ParamSet.ServoNickMin;
                        ToNaviCtrl.Param.Byte[5] = ParamSet.ServoNickMax;
                        ToNaviCtrl.Param.Byte[6] = FCParam.ServoRollControl;
                        ToNaviCtrl.Param.Byte[7] = ParamSet.ServoRollComp;
                        ToNaviCtrl.Param.Byte[8] = ParamSet.ServoRollMin;
                        ToNaviCtrl.Param.Byte[9] = ParamSet.ServoRollMax;
                        break;

                default:
                        break;
        }

        // analyze content of packet from NaviCtrl if valid
        if (SPI_RxDataValid)
        {
                // update gps controls
                if(abs(FromNaviCtrl.GPSStickNick) < 512 && abs(FromNaviCtrl.GPSStickRoll) < 512 && (ParamSet.Config0 & CFG0_GPS_ACTIVE))
                {
                        GPSStickNick    = FromNaviCtrl.GPSStickNick;
                        GPSStickRoll    = FromNaviCtrl.GPSStickRoll;
                        NCDataOkay = 250;
                }
                // update compass readings
                if(FromNaviCtrl.CompassHeading <= 360)
                {
                        CompassHeading = FromNaviCtrl.CompassHeading;
                }
                if(CompassHeading < 0) CompassOffCourse = 0;
                else CompassOffCourse = ((540 + CompassHeading - CompassCourse) % 360) - 180;
        // NaviCtrl wants to beep?
                if (FromNaviCtrl.BeepTime > BeepTime && !CompassCalState) BeepTime = FromNaviCtrl.BeepTime;

                switch (FromNaviCtrl.Command)
                {

                        case SPI_KALMAN:
                                FCParam.KalmanK = FromNaviCtrl.Param.sByte[0];
                                FCParam.KalmanMaxFusion = FromNaviCtrl.Param.sByte[1];
                                FCParam.KalmanMaxDrift = FromNaviCtrl.Param.sByte[2];
                                NCSerialDataOkay = FromNaviCtrl.Param.Byte[3];
                                NCGpsZ = FromNaviCtrl.Param.sByte[4];
                                break;

                        default:
                                break;
                }
        }
        else // no valid data from NaviCtrl
        {
                // disable GPS control
                GPSStickNick = 0;
                GPSStickRoll = 0;
                NCGpsZ = 0;
        }
}



/*********************************************/
/*  Start Transmission of packet to NaviCtrl */
/*********************************************/
void SPI_StartTransmitPacket(void)
{

        if (!SPITransferCompleted) return; // return immediately if transfer is in progress
        else // transmission was completed
        {
                SLAVE_SELECT_PORT &=  ~(1 << SPI_SLAVE_SELECT);  // Select slave

                // cyclic commands
                ToNaviCtrl.Command = SPI_CommandSequence[SPI_CommandCounter++];
                if (SPI_CommandCounter >= sizeof(SPI_CommandSequence)) SPI_CommandCounter = 0;

                SPITransferCompleted = 0; // transfer is in progress
                UpdateSPI_Buffer();    // update data in ToNaviCtrl

                SPI_TxBufferIndex = 1; //proceed with 2nd byte

                // -- Debug-Output ---
                //----
                asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop");            asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop");
                asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop");            asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop");
                asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop");            asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop");
                ToNaviCtrl.Chksum = ToNaviCtrl.Sync1; // init checksum
                SPDR = ToNaviCtrl.Sync1; // send first byte
        }
}

//------------------------------------------------------
// This is the spi data transfer between FlightCtrl and NaviCtrl
// Every time this routine is called within the mainloop one byte of the packet to
// the NaviCtrl and one byte of the packet from the NaviCtrl is possible transfered

void SPI_TransmitByte(void)
{
        static SPI_RXState_t SPI_RXState = SPI_SYNC1;
        uint8_t rxdata;
        static uint8_t rxchksum;

        if (SPITransferCompleted) return;  // return immediatly if transfer was completed
        if (!(SPSR & (1 << SPIF))) return; // return if no SPI-IRQ pending
        SendSPI = 4; // mait 4 * 0.102 ms for the next call of SPI_TransmitByte() in the main loop

        SLAVE_SELECT_PORT |=  (1 << SPI_SLAVE_SELECT);   // DeselectSlave

        rxdata = SPDR; // save spi data register

        switch (SPI_RXState)
        {
                case SPI_SYNC1: // first sync byte
                        SPI_RxBufferIndex = 0; // set pointer to start of rx buffer
                        rxchksum = rxdata; // initialize checksum
                        if (rxdata == SPI_RXSYNCBYTE1 )
                        {       // 1st Syncbyte found
                                SPI_RXState  = SPI_SYNC2; // trigger to state for second sync byte
                        }
                        break;

                case SPI_SYNC2: // second sync byte
                        if (rxdata == SPI_RXSYNCBYTE2)
                        {       // 2nd Syncbyte found
                                rxchksum += rxdata; // update checksum
                                SPI_RXState  = SPI_DATA;   // trigger to state for second sync byte
                        }
                        else // 2nd Syncbyte not found
                        {
                                SPI_RXState  = SPI_SYNC1; // jump back to 1st sync byte
                        }
                        break;

                case SPI_DATA: // data bytes
                        SPI_RxBuffer[SPI_RxBufferIndex++] = rxdata;  // copy data byte to spi buffer
                        // if all bytes are received of a packet from the NaviCtrl
                        if (SPI_RxBufferIndex >= SPI_RXBUFFER_LEN)
                        {   // last byte transfered is the checksum of the packet
                                if (rxdata == rxchksum) // checksum matching?
                                {
                                        // copy SPI_RxBuffer -> FromFlightCtrl
                                        uint8_t *ptr = (uint8_t *)&FromNaviCtrl;
                                        cli();
                                        memcpy(ptr, (uint8_t *) SPI_RxBuffer, sizeof(FromNaviCtrl));
                                        sei();
                                        SPI_RxDataValid = 1;
                                        //DebugOut.Analog[18]++;
                                }
                                else
                                {   // checksum does not match
                                        //DebugOut.Analog[17]++;
                                        SPI_RxDataValid = 0; // reset valid flag
                                }
                                SPI_RXState  = SPI_SYNC1; // reset state sync
                        }
                        else // not all bytes transfered
                        {
                                rxchksum += rxdata; // update checksum
                        }
                        break;
        }// eof switch(SPI_RXState)

    // if still some bytes left for transmission to NaviCtrl
        if (SPI_TxBufferIndex < SPI_TXBUFFER_LEN)
        {
                SLAVE_SELECT_PORT &=  ~(1 << SPI_SLAVE_SELECT);  // SelectSlave
                asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop");
                asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop");
                asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop"); asm volatile ("nop");

                SPDR = SPI_TxBuffer[SPI_TxBufferIndex]; // transmit byte
                ToNaviCtrl.Chksum += SPI_TxBuffer[SPI_TxBufferIndex]; // update checksum for everey byte that was sent
                SPI_TxBufferIndex++;
        }
        else
        {
                //Transfer of all bytes of the packet to NaviCtrl completed
                SPITransferCompleted = 1;
        }
}