Method conditionResponse

src/ELMduino.cpp:490–562

double ELM327::conditionResponse(const uint8_t &numExpectedBytes, const float &scaleFactor, const float &bias) Description: ------------ * Converts the ELM327's response into its correct, numerical value. Returns 0 if numExpectedBytes > numPayChars Inputs: ------- * uint64_t response - ELM327's response * uint8_t numExpectedBytes - Number of valid bytes from the respons

  * double - Converted numerical value
*/
double ELM327::conditionResponse(const uint8_t& numExpectedBytes,
                                 const double&  scaleFactor,
                                 const double&   bias)
{
    uint8_t numExpectedPayChars = numExpectedBytes * 2;
    uint8_t payCharDiff         = numPayChars - numExpectedPayChars;

    if (numExpectedBytes > 8)
    {
        if (debugMode)
            Serial.println(F("WARNING: Number of expected response bytes is greater than 8 - returning 0"));

        return 0;
    }

    if (numPayChars < numExpectedPayChars)
    {
        if (debugMode)
            Serial.println(F("WARNING: Number of payload chars is less than the number of expected response chars returned by ELM327 - returning 0"));

        return 0;
    }
    else if (numPayChars & 0x1)
    {
        if (debugMode)
            Serial.println(F("WARNING: Number of payload chars returned by ELM327 is an odd value - returning 0"));

        return 0;
    }
    else if (numExpectedPayChars == numPayChars)
    {
        if (scaleFactor == 1 && bias == 0) // No scale/bias needed
            return response;
        else
            return (response * scaleFactor) + bias;
    }

    // If there were more payload bytes returned than we expected, test the first and last bytes in the
    // returned payload and see which gives us a higher value. Sometimes ELM327's return leading zeros
    // and others return trailing zeros. The following approach gives us the best chance at determining
    // where the real data is. Note that if the payload returns BOTH leading and trailing zeros, this
    // will not give accurate results!

    if (debugMode)
        Serial.println(F("Looking for lagging zeros"));

    uint16_t numExpectedBits  = numExpectedBytes * 8;
    uint64_t laggingZerosMask = 0;

    for (uint16_t i = 0; i < numExpectedBits; i++)
        laggingZerosMask |= (1 << i);

    if (!(laggingZerosMask & response)) // Detect all lagging zeros in `response`
    {
        if (debugMode)
            Serial.println(F("Lagging zeros found"));

        if (scaleFactor == 1 && bias == 0) // No scale/bias needed