LoRaMacStatus_t PrepareFrame( LoRaMacHeader_t* macHdr, LoRaMacFrameCtrl_t* fCtrl, uint8_t fPort, void* fBuffer, uint16_t fBufferSize )
{
    MacCtx.PktBufferLen = 0;
    MacCtx.NodeAckRequested = false;
    uint32_t fCntUp = 0;
    size_t macCmdsSize = 0;
    uint8_t availableSize = 0;

    if( fBuffer == NULL )
    {
        fBufferSize = 0;
    }

    memcpy1( MacCtx.AppData, ( uint8_t* ) fBuffer, fBufferSize );
    MacCtx.AppDataSize = fBufferSize;
    MacCtx.PktBuffer[0] = macHdr->Value;

    switch( macHdr->Bits.MType )
    {
        case FRAME_TYPE_DATA_CONFIRMED_UP:
            MacCtx.NodeAckRequested = true;
            // Intentional fall through
        case FRAME_TYPE_DATA_UNCONFIRMED_UP:
            MacCtx.TxMsg.Type = LORAMAC_MSG_TYPE_DATA;
            MacCtx.TxMsg.Message.Data.Buffer = MacCtx.PktBuffer;
            MacCtx.TxMsg.Message.Data.BufSize = LORAMAC_PHY_MAXPAYLOAD;
            MacCtx.TxMsg.Message.Data.MHDR.Value = macHdr->Value;
            MacCtx.TxMsg.Message.Data.FPort = fPort;
            MacCtx.TxMsg.Message.Data.FHDR.DevAddr = MacCtx.NvmCtx->DevAddr;
            MacCtx.TxMsg.Message.Data.FHDR.FCtrl.Value = fCtrl->Value;
            MacCtx.TxMsg.Message.Data.FRMPayloadSize = MacCtx.AppDataSize;
            MacCtx.TxMsg.Message.Data.FRMPayload = MacCtx.AppData;

            if( LORAMAC_CRYPTO_SUCCESS != LoRaMacCryptoGetFCntUp( &fCntUp ) )
            {
                return LORAMAC_STATUS_FCNT_HANDLER_ERROR;
            }
            MacCtx.TxMsg.Message.Data.FHDR.FCnt = ( uint16_t )fCntUp;

            // Reset confirm parameters
            MacCtx.McpsConfirm.NbRetries = 0;
            MacCtx.McpsConfirm.AckReceived = false;
            MacCtx.McpsConfirm.UpLinkCounter = fCntUp;

            // Handle the MAC commands if there are any available
            if( LoRaMacCommandsGetSizeSerializedCmds( &macCmdsSize ) != LORAMAC_COMMANDS_SUCCESS )
            {
                return LORAMAC_STATUS_MAC_COMMAD_ERROR;
            }

            if( macCmdsSize > 0 )
            {
                availableSize = GetMaxAppPayloadWithoutFOptsLength( MacCtx.NvmCtx->MacParams.ChannelsDatarate );

                // There is application payload available and the MAC commands fit into FOpts field.
                if( ( MacCtx.AppDataSize > 0 ) && ( macCmdsSize <= LORA_MAC_COMMAND_MAX_FOPTS_LENGTH ) )
                {
                    if( LoRaMacCommandsSerializeCmds( LORA_MAC_COMMAND_MAX_FOPTS_LENGTH, &macCmdsSize, MacCtx.TxMsg.Message.Data.FHDR.FOpts ) != LORAMAC_COMMANDS_SUCCESS )
                    {
                        return LORAMAC_STATUS_MAC_COMMAD_ERROR;
                    }
                    fCtrl->Bits.FOptsLen = macCmdsSize;
                    // Update FCtrl field with new value of FOptionsLength
                    MacCtx.TxMsg.Message.Data.FHDR.FCtrl.Value = fCtrl->Value;
                }
                // There is application payload available but the MAC commands does NOT fit into FOpts field.
                else if( ( MacCtx.AppDataSize > 0 ) && ( macCmdsSize > LORA_MAC_COMMAND_MAX_FOPTS_LENGTH ) )
                {

                    if( LoRaMacCommandsSerializeCmds( availableSize, &macCmdsSize, MacCtx.NvmCtx->MacCommandsBuffer ) != LORAMAC_COMMANDS_SUCCESS )
                    {
                        return LORAMAC_STATUS_MAC_COMMAD_ERROR;
                    }
                    return LORAMAC_STATUS_SKIPPED_APP_DATA;
                }
                // No application payload available therefore add all mac commands to the FRMPayload.
                else
                {
                    if( LoRaMacCommandsSerializeCmds( availableSize, &macCmdsSize, MacCtx.NvmCtx->MacCommandsBuffer ) != LORAMAC_COMMANDS_SUCCESS )
                    {
                        return LORAMAC_STATUS_MAC_COMMAD_ERROR;
                    }
                    // Force FPort to be zero
                    MacCtx.TxMsg.Message.Data.FPort = 0;

                    MacCtx.TxMsg.Message.Data.FRMPayload = MacCtx.NvmCtx->MacCommandsBuffer;
                    MacCtx.TxMsg.Message.Data.FRMPayloadSize = macCmdsSize;
                }
            }

            break;
        case FRAME_TYPE_PROPRIETARY:
            if( ( fBuffer != NULL ) && ( MacCtx.AppDataSize > 0 ) )
            {
                memcpy1( MacCtx.PktBuffer + LORAMAC_MHDR_FIELD_SIZE, ( uint8_t* ) fBuffer, MacCtx.AppDataSize );
                MacCtx.PktBufferLen = LORAMAC_MHDR_FIELD_SIZE + MacCtx.AppDataSize;
            }
            break;
        default:
            return LORAMAC_STATUS_SERVICE_UNKNOWN;
    }

    return LORAMAC_STATUS_OK;
}