Method decodeOpenLASIR

src/ir_OpenLASIR.hpp:229–307

* Decode an OpenLASIR frame. * * OpenLASIR uses the same physical layer as NEC but with different address/command structure: * - 8-bit address with inverted complement (error check on address) * - 16-bit command without error check * * The decoder validates the address by checking that the second byte is the bitwise * inverse of the first byte. The full 16-bit command is returned as-is.

 * @return true if a valid OpenLASIR frame was decoded.
 */
bool IRrecv::decodeOpenLASIR() {
    /*
     * First check for right data length
     * Next check start bit
     * Next try the decode
     */

    // Check we have the right amount of data (68). The +4 is for initial gap, start bit mark and space + stop bit mark.
    if (!(decodedIRData.rawlen == ((2 * OPENLASIR_BITS) + 4) || (decodedIRData.rawlen == 4))) {
        DEBUG_PRINT(F("OpenLASIR: Data length="));
        DEBUG_PRINT(decodedIRData.rawlen);
        DEBUG_PRINTLN(F(" is not 68 or 4"));
        return false;
    }

    // Check header "mark" - this must be done for repeat and data
    if (!matchMark(irparams.rawbuf[1], NEC_HEADER_MARK)) {
        return false;
    }

#if !defined(DECODE_NEC) // This code is also contained in NEC sources and does also decode LASIR Repeats :-)
    // Check for repeat - here we have another header space length
    if (decodedIRData.rawlen == 4) {
        if (matchSpace(irparams.rawbuf[2], NEC_REPEAT_HEADER_SPACE) && matchMark(irparams.rawbuf[3], NEC_BIT_MARK)) {
            decodedIRData.flags = IRDATA_FLAGS_IS_REPEAT | IRDATA_FLAGS_IS_LSB_FIRST;
            decodedIRData.address = lastDecodedAddress;
            decodedIRData.command = lastDecodedCommand;
            decodedIRData.protocol = lastDecodedProtocol; // Allow recognition of repeats of another look alike protocol
            return true;
        }
        return false;
    }
#endif

    // Check command header space
    if (!matchSpace(irparams.rawbuf[2], NEC_HEADER_SPACE)) {
        DEBUG_PRINTLN(F("OpenLASIR: Header space length is wrong"));
        return false;
    }

    // Decode the pulse distance data using NEC timing
    decodePulseDistanceWidthData_P(&NECProtocolConstants, OPENLASIR_BITS);

    // Success - now interpret the 32 raw bits
    LongUnion tValue;
    tValue.ULong = decodedIRData.decodedRawData;

    // Validate address: second byte must be inverted first byte
    if (tValue.UByte.LowByte != (uint8_t)(~tValue.UByte.MidLowByte)) {
        // Address validation failed - this is not a valid OpenLASIR frame
        DEBUG_PRINTLN(F("OpenLASIR: Address validation failed"));
        return false;
    }

    /*
     * Disambiguation with standard NEC:
     * If the command also has a valid inverted pattern (upper 8 bits == ~lower 8 bits),
     * then this looks like a standard NEC frame, not OpenLASIR.