c2-utopia/lib/RTArduLink/RTArduLinkUtils.cpp

///////////////////////////////////////////////////////////
//
//  This file is part of RTArduLink
//
//  Copyright (c) 2014-2015 richards-tech
//
//  Permission is hereby granted, free of charge,
//  to any person obtaining a copy of
//  this software and associated documentation files
//  (the "Software"), to deal in the Software without
//  restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute,
//  sublicense, and/or sell copies of the Software, and
//  to permit persons to whom the Software is furnished
//  to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice
//  shall be included in all copies or substantial portions
//  of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
//  ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
//  TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
//  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
//  THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
//  CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
//  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
//  IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
//  DEALINGS IN THE SOFTWARE.

#include "RTArduLinkUtils.h"

//	RTArduLinkRXFrameInit initializes the structure for a new frame using frameBuffer for storage

void RTArduLinkRXFrameInit(RTARDULINK_RXFRAME *RXFrame, RTARDULINK_FRAME *frameBuffer)
{
    RXFrame->complete = false;
    RXFrame->length = 0;
    RXFrame->bytesLeft = 0;
    RXFrame->frameBuffer = frameBuffer;
}

//  RTArduLinkReassemble takes a sequence of received bytes and tries to complete a frame. It returns true if ok
//  false if error. The caller can determine if the frame is complete by checking the complete flag.

bool RTArduLinkReassemble(RTARDULINK_RXFRAME *RXFrame, unsigned char data)
{
    bool flag = true;

    ((unsigned char *)(RXFrame->frameBuffer))[RXFrame->length] = data;  // save byte in correct place
    switch (RXFrame->length) {
        case 0:                                             // waiting for sync0
            if (RXFrame->frameBuffer->sync0 == RTARDULINK_MESSAGE_SYNC0) {
                RXFrame->length = 1;
            }
            break;

        case 1:                                             // waiting for sync1
            if (RXFrame->frameBuffer->sync1 == RTARDULINK_MESSAGE_SYNC1) {
                RXFrame->length = 2;
            } else {
                RXFrame->length = 0;                        // try again if not correct two byte sequence
            }
            break;

        case 2:                                             // should be message length
            if (RXFrame->frameBuffer->messageLength <= RTARDULINK_MESSAGE_MAX_LEN) {
                RXFrame->length = 3;
                RXFrame->bytesLeft = RXFrame->frameBuffer->messageLength + 1;   // +1 to allow for the checksum
            } else {
                RXFrame->length = 0;                        // discard this and resync frame
                flag = false;
            }
            break;

        default:
            RXFrame->length++;
            RXFrame->bytesLeft--;
            if (RXFrame->bytesLeft == 0) {                  // a complete frame!
                if (!RTArduLinkCheckChecksum(RXFrame->frameBuffer)) {
                    RTArduLinkRXFrameInit(RXFrame, RXFrame->frameBuffer);
                    flag = false;                           // flag the error
                } else {
                    //  this is a valid frame (so far)
                    RXFrame->complete = true;
                }
            }
            break;
    }
    return flag;
}

//  RTArduLinkSetChecksum correctly sets the checksum field on an RCP frame prior to transmission
//

void RTArduLinkSetChecksum(RTARDULINK_FRAME *frame)
{
    int cksm;
    int i;
    unsigned char *data;

    for (i = 0, cksm = 0, data = (unsigned char *)&(frame->message); i < frame->messageLength; i++)
        cksm += *data++;                                    // add up checksum
    frame->frameChecksum = (255 - cksm) + 1;                // 2s complement
}


//  RTArduLinkCheckChecksum checks a received frame's checksum.
//
//  It adds up all the bytes from the nFrameCksm byte to the end of the frame. The result should be 0.

bool RTArduLinkCheckChecksum(RTARDULINK_FRAME *frame)
{
    int length;
    int i;
    unsigned char *data;
    unsigned char cksm;

    length = frame->messageLength + 1;
    cksm = 0;
    data = (unsigned char *)&(frame->frameChecksum);

    for (i = 0; i < length; i++)
        cksm += *data++;

    return cksm == 0;
}

//  UC2 and UC4 Conversion routines
//

long RTArduLinkConvertUC4ToLong(RTARDULINK_UC4 UC4)
{
    long val;

    val = UC4[3];
    val += (long)UC4[2] << 8;
    val += (long)UC4[1] << 16;
    val += (long)UC4[0] << 24;
    return val;
}

void RTArduLinkConvertLongToUC4(long val, RTARDULINK_UC4 UC4)
{
    UC4[3] = val & 0xff;
    UC4[2] = (val >> 8) & 0xff;
    UC4[1] = (val >> 16) & 0xff;
    UC4[0] = (val >> 24) & 0xff;
}

int RTArduLinkConvertUC2ToInt(RTARDULINK_UC2 UC2)
{
    int val;

    val = UC2[1];
    val += (int)UC2[0] << 8;
    return val;
}

unsigned int RTArduLinkConvertUC2ToUInt(RTARDULINK_UC2 UC2)
{
    unsigned int val;

    val = UC2[1];
    val += (unsigned int)UC2[0] << 8;
    return val;
}


void RTArduLinkConvertIntToUC2(int val, RTARDULINK_UC2 UC2)
{
    UC2[1] = val & 0xff;
    UC2[0] = (val >> 8) & 0xff;
}


void RTArduLinkCopyUC2(RTARDULINK_UC2 destUC2, RTARDULINK_UC2 sourceUC2)
{
    destUC2[0] = sourceUC2[0];
    destUC2[1] = sourceUC2[1];
}