Lufft VENTUS-UMB - Communication in Binary Protocol

Operating Manual V25/09.2019 Ventus / Ventus-X / V200A
Chapter 20 Appendix 40
20.3 Communication in Binary Protocol
Only one example of an online data request is described in this operating manual. Please refer
to the current version of the UMB Protocolfor all commands and the exact mode of operation of
the protocol (available for download at www.lufft.com).
Note: Communication with the sensor takes place in accordance with the master-slave
principle, i.e. there may only be ONE requesting unit on a network.
20.3.1 Framing
The data frame is constructed as follows:
SOH Control character for the start of a frame (01h); 1 byte
<ver> Header version number, e.g.: V 1.0 <ver> = 10h = 16d; 1 byte
<to> Receiver address; 2 bytes
<from> Sender address; 2 bytes
<len> Number of data bytes between STX and ETX; 1 byte
STX Control character for the start of payload transmission (02h); 1 byte
<cmd> Command; 1 byte
<verc> Version number of the command; 1 byte
<payload> Data bytes; 0 – 210 bytes
ETX Control character for the end of payload transmission (03h); 1 byte
<cs> Check sum, 16 bit CRC; 2 bytes
EOT Control character for the end of the frame (04h); 1 byte
Control characters: SOH (01h), STX (02h), ETX (03h), EOT (04h).
20.3.2 Addressing with Class and Device ID
Addressing takes place by way of a 16 bit address. This breaks down into a Class ID and a
Device ID.
Address (2 bytes = 16 bit)
Bits 15 – 12 (upper 4 bits)
Bits 11 – 8
(middle 4 bits)
Bits 7 – 0 (lower 8 bits)
Class ID (0 to 15)
Reserve
Device ID (0 – 255)
0
Broadcast
0
Broadcast
8
Ventus
1 - 255
Available
15
Master or control devices
ID = 0 is provided as broadcast for classes and devices. Thus it is possible to transmit a
broadcast on a specific class. However this only makes sense if there is only one device of this
class on the bus; or in the case of a command, e.g. reset.
20.3.3 Examples for Creating Addresses
If, for example, you want to address Ventus with the device ID 001, this takes place as follows:
The class ID for the Ventus is 8d = 8h;
the device ID is e.g. 001d = 01h
Putting the class and device IDs together gives the address 8001h (32769d).
20.3.4 Example of a Binary Protocol Request
If, for example, a Ventus with the device ID 001 is to be polled from a PC for the current
temperature, this takes place as follows:
1
2
3 - 4
5 - 6
7
8
9
10
11 ... (8 + len)
optional
9 + len
10 + len
11 + len
12 + len
SOH
<ver>
<to>
<from>
<len>
STX
<cmd>
<verc>
<payload>
ETX
<cs>
EOT