INFICON Helium Leak Detector Modul1000 Interface description - Manual (Page 16)

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Binary Protocol
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4 Binary Protocol
4.1 Command Structure
In binary protocol the command to the leak detector always starts with STX (0x05).
It is followed by a byte which indicates the length of the telegram (inclusive Start-Byte
and checksum). The next byte is the command number. The command byte may be
followed by additional information (parameter and/or data). Please refer to
"Command list" (chapter 4.5) for detailed information about command number,
parameter and data format.
Every telegram ends with a checksum. The checksum is the sum of all bytes before
the checksum byte modulo 256 (decimal).
The leak detector replies to every valid command with an acknowledgement. This
answer starts with the length byte followed by the command number, additional data
(optional) and the checksum.
In case of an error, the leak detector answers with an error byte instead of the
command number (refer to "Error Messages" in chapter 4.4).
Timeout to receive data between 2 sign is: 1000 ms.
4.2 Examples
Example 1: Set trigger level 2 to 1.2E-7mbarl/s
PC Î Leak detector
Leak detector Î PC
5 10 57 2 0 52 0 217 89 176
0x05 0x0A 0x39 0x02 0x00 0x34 0x00 0xD9 0x59 0xB0
Start Length Command Para0 Para1 Data Data Data Data Checksum
Trigger Trig. 2 mbarl/s 1.2E-7 (4-Byte float)
3 57 60
0x03 0x39 0x3C
Length Command Checksum