Lufft CHM 15k, User Manual

Page: 31 / 73

Operating Manual CHM 15k R13 / 07-2019
Communication via RS485 & Ethernet 31
8.2 Device configuration with RS485
The user can change settings via the RS485 interface:
•
for controlling the measuring processes
•
for configuring the communication interfaces
8.2.1 Reading out a parameter
Querying a parameter takes place via the command:
get<SPACE><RS485Number>:<ParameterName><CR><LF>
If <ParameterName> contains a valid name according to Table 4 or Table 5, the value is delivered via
<STX>get<SPACE><Device>:<ParameterName>=<Value>;<ASCIITwo
’sComplement><CR><LF><E
OT>.
Example with the default RS485Number = 16 and the device name = CHM060003
The short command
get 16: DVN<CR><LF>
can be used to query the device name and receive a response, here:
<STX>get 16:DeviceName=CHM060003;3F<CR><LF><EOT>.
Each of the non-printable characters <STX>, <CR>, <LF> and <EOT> stand for one byte with
hexadecimal codes 02, 0D, 0A and 04. The characters 3F represents the checksum of the two's
complement formed over the whole response line, excluding these two characters (3F) in accordance
with the protocol response formats (
see 0
Standard data telegram to 8.3.5 Raw data telegram ).
8.2.2 Setting a parameter
A configuration parameter is changed via the command
set<SPACE><RS485Number>:<ParameterName>=<Value><CR><LF>
A successful change is confirmed with
<STX>set<SPACE><RS485Number>:<ParameterName>=<Value*>;<
ASCIIT o’sComplement><CR
><LF><EOT>
If <value> in the query command is within the limits of the permissible value range, the newly set value
<value*> also corresponds to this parameter. If the values are too small (too large), the minimum (maximum)
of the permissible range is used. For alphanumeric values as <value>, the default value is used.
Example with RS485Number = 16:
With the command
set 16:Unit(m/ft)=ft<CR><LF>
or in the short form
set 16:UNT=ft<CR><LF>
the value of all range dependent parameters in the protocol responses is changed from the default meters
(m) to feet (ft) scale. Since Unit(m/ft) belongs to the changeable parameters, it should be confirmed with
<STX>set 16:Unit(m/ft)=ft;2A<CR><LF><EOT>
The value 2A is the checksum of the response line.
8.2.3 Changing the baud rate
The option to change the baud rate is a specific feature. The change takes place as described in 8.2.2
Setting a parameter. Thus, baud rate no. 4 that corresponds to 19,200 bits/s is set with
set<SPACE><RNO>:Baud=4<CR><LF>
The correlation between baud rate #. and baud rate is shown in Table 6 .