THCD-401 Instruction Manual
Page 30 of 47
6. Serial & TCP Communication
Introduction
The THCD-401 allows full control and feedback via TCP/IP and RS232 (via USB) communications protocols. All
controls via HMI are also available via comms and all calibration is also performed via comms commands.
Please note that the RS232 serial port is not configurable. The fixed baud rate is 57600 with other settings as
follows: 8 data bits, 1 stop bit, No parity, No handshaking.
TCP/IP comms requires an IP address and subnet mask to be configured for the THCD. This can be set via the
HMI, webserver or via serial comms. Note that on changing the IP address or subnet mask, the THCD must be
re-initialized by performing a system reset. This is done automatically if setting from comms (the THCD waits a
second and then resets itself) or from the webserver, but if setting from the HMI, you must power off & on for
the new TCP/IP settings to come into effect.
Note for the host connection, the TCP port of the THCD-401 is port 101.
Command/Query format
The format of the commands and queries is common between all available comms protocols for ease of use and
understanding when switching between comms methods:
Format: accc[?] [p][,p][,p]
↵
… where ‘a’ = address, ‘ccc’ = command/query, ‘?’ = query identification; ‘p’ = parameter (separated by
commas if more than one)
The first letter to be entered on the command line, before any command or query, is the address identifier.
The is a legacy character left in to provide some level of backwards compatibility and familiarity with Chell’s
remote comms protocol from earlier display models. It can no longer be configured and is now fixed to the
character ‘a’. On TCP/IP this address doesn’t really mean anything because TCP/IP uses an IP address per unit
for identification.
Most commands are identified by three letters (although this is not always the case) and a query is identified
by following the command letters with a ‘?’ character. For all commands with parameters, you must separate
the command from its parameters with a space, and separate multiple parameters with commas.
Table 1 in Appendix A summarizes all commands and queries available. Note that where a command is also a
query, you do not enter any parameters for the query ‘version’ unless explicitly stated in the table.
For everything sent on the comms port, the THCD will reply by informing of the command/query it has just
received, along with any parameters identified, any data requested (if it was a valid command/query) and a
line indicating whether the command was accepted. This reply block is the same for anything sent to the THCD
and is as follows.
(‘
↵
’ indicates a carriage return/line feed pair):
For a command:
*<a>*:<cmd>;<params>
↵
!<a>!<response>!
↵
For a query:
*<a>*:<cmd>;<params>
↵
<data>
↵
!<a>!<response>!
↵
where:
<a> is the address letter
