class TwePacket {
    public:
        static const E_PKT _pkt_id = E_PKT::PKT_ERROR;
        
        struct {
            uint32_t tick; // system time at interpretation execution [ms]
            uint32_t src_addr; // source address (serial number)
            uint8_t src_lid; // source address (logical address)
            uint8_t lqi; // LQI
            uint16_t volt; // voltage[mV]
        } common;
};

This is used when you want to get minimum information such as address information when you want to store mixed types as pktparser type in arrays, etc.