protocol.txt

0000   02 03 20 1b 00 17 00 04 00 1b 0c 00 [ff 55 01 01
0010   00 08 f6 00 0e df 00 1c 18 00 00 00  31 06 1a b1]   20 bytes

0000   02 03 20 17 00 13 00 04 00 1b 0c 00 [01 f3 03 37
0010   00 1a 00 00 00 00 3c 00 00 00 00 e3]                16 bytes

0000   [ff 55 01 01  00 08 f6 00 0e df 00 1c 18 00 00 00
0010    31 06 1a b1][01 f3 03 37 00 1a 00 00 00 00 3c 00
0020    00 00 00 e3]                                       36 bytes

Protocol:
    0000-0001   Magic Number        FF55
    0002        Select              01 = Receive    11 = Send
    0003        Device Type
    0004-0006   Voltage
    0007-0009   Current
    000A-000C   Power
    000D-0010   Energy
    0011-0013   Unit Price
    0014-0015   Frequency
    0016-0017   Power Factor
    0018-0019   Temperature
    001A-001C   Unknown
    001E        Back Light Mode     00 = Black  3C = Light  01-3B = Seconds
    001F-0022   Unknown
    0023        Checksum            (0002 + ... + 0022) ^ 0x44 & 0xFF

UUID:
    0000ffe0-0000-1000-8000-00805f9b34fb    Service
    0000ffe1-0000-1000-8000-00805f9b34fb    Notify      <- Subscribe, Write

Commands:
    OP      CMD             PARAM1      PARAM2      PARAM3      COMMENT
    0x01    Clear           00          00          00
    0x22    Set Unit Price  & 0xFF0000  & 0x00FF00  & 0x0000FF  0x000001 (0.01) ~ 0x0F423F (9999.99)
    0x31    Set
    0x32    OK
    0x33    Plus
    0x34    Minus