Busch Welcome ABB Welcome Doorbell Message Format

struct MessageHeader {
    unsigned preamble:16; // 0x55ff
    unsigned retransmissionFlag:1;
    unsigned payloadLength:7;
    unsigned replyFlag:1;
    unsigned messageType:7;
    unsigned destinationDeviceType:4;
    unsigned destinationAddress:12;
    unsigned sourceDeviceType:4;
    unsigned sourceAddress:12;
    unsigned messageID:8; // must be randomly generated
};

// Message: Header + Payload + Checksum

enum MessageType {
    DoorbellOutdoor = 0x01,
    EndCall = 0x02,
    AcceptCall = 0x03,
    ManualVideo = 0x04,
    Light = 0x09,
    Call = 0x0a,
    Door = 0x0d,
    DoorbellIndoor = 0x11,
    Actor = 0x16,
    Video = 0x52,
};

enum DeviceType {
    IndoorStation = 0x1,
    OutdoorStation = 0x2,
    Gateway = 0x3,
    Relay = 0x4,
    Actor = 0x8,
    Video = 0x9,
};

uint8_t calculateChecksum(uint8_t *data, uint8_t length) {
    uint8_t checksum = 0;
    for (uint8_t i = 0; i < length; i++)
        checksum = nextChecksum(*data++, checksum);
    return ~checksum & 0xff;
}

uint8_t nextChecksum(uint8_t data, uint8_t lastChecksum) {
    uint16_t temp = lastChecksum ^ data;
    temp = temp ^
        (uint16_t)(((uint32_t)temp << 0x11) >> 0x10) ^
        (uint16_t)(((uint32_t)temp << 0x12) >> 0x10) ^
        (uint16_t)(((uint32_t)temp << 0x13) >> 0x10) ^
        (uint16_t)(((uint32_t)temp << 0x14) >> 0x10) ^
        (uint16_t)(((uint32_t)temp << 0x15) >> 0x10) ^
        (uint16_t)(((uint32_t)temp << 0x16) >> 0x10) ^
        (uint16_t)(((uint32_t)temp << 0x17) >> 0x10);
    return (temp & 0xfe) ^ ((temp >> 8) & 1);
}