Filter
Top Products
Model MX88 Page: 29
© 2010 Xantech LLC
Appendix
RS232 CONTROL
This document describes the bi-directional RS232 interface of the MX88 using the two COM PORTs on the rear
of the system (Fig. 3 item 29). This interface allows an external RS232 device to control the MX88 via a set of
ASCII text commands. It is also possible to control any IR device connected to the MX88 system as well by
triggering individual IR Commands and/or IR Macros via ASCII strings.
TYPES OF COMMANDS
There are two types of information that can be sent to the MX88 Controller: COMMANDS and QUERIES.
COMMANDS are ASCII strings used to set a specific parameter in the system (i.e. Select a Source, turn a zone
ON, start a DVD player etc…). QUERIES are requests for system status information and result in the MX88
controller sending back a reply to the string being sent (i.e. seeing what zones are on, which sources are
selected and volume settings etc….)
INTERFACING TO THE RS232 COM PORTs
The RS232 Com Ports on the rear of the MX88 Controller, when used with the included DB15-DB9 adaptors,
are wired as a „null modem‟ end, meaning the Transmit and Receive line have already been interchanged for
direct communication with a PC. What this means is when connecting to a standard PC‟s Com Port, no Null
Modem cable is necessary.
The pin out configuration for this connector is:
COM PORT (with DB15-DB9 adaptor)
PIN #
FUNCTION
1, 7, 8, & 9
NC
2
Tx
3
Rx
4
DSR
5
GND
6
DTR
Rear Com Port Connector Pin Out
ASCII STRING „INITIATING‟ AND „TERMINATING‟ CHARACTERS
The parsing of incoming data on the COM PORT can be disabled via a setting in the Universal Dragon project.
This might be necessary if the COM port is to be used to control an external device and any incoming data from
that device is to be ignored. This setting can be found with the settings for configuring the COM port.
For the MX88 system to recognize incoming ASCII command strings, the string must begin with an „!‟ and for
data queries the string must begin with a „?‟. All strings must end with a „+‟. This way it can determine the
beginning and end of the string for processing.
When a proper command is sent, an ASCII acknowledgement string of OK is returned to the issuing device. If
an unrecognizable string is received, an ASCII string of ERROR is returned to the issuing device.
Example #1: (Issuing a Command String);
To turn Zone 7 ON:
Send ASCII string: !7PR1+
MX88 Controller Reply: OK