Specifications

Crestron SIMPL Windows Software
Because of the absence of a driver file, RS-232 control is generally considered more
difficult to program than IR or custom serial. This is because each time an RS-232
device is to be programmed, the programmer must look up the protocol in the
manual, and then write the necessary logic into his program to send this data. To
counter this, many devices have dedicated modules written for them. These modules
can be plugged into a program and used to generate all the proper control codes
automatically.
The differences between RS-232, RS-422, and RS-485 are physical in nature, and do
not affect the programmer, except that they must make sure that the Crestron product
being used to send the data supports the format, and has been configured properly.
RS-232 uses one wire to transmit data, and one wire to receive it. It is generally valid
for sending data up to 50 feet, but this distance can depend on many factors, such as
cable quality, baud rate, and the ambient electrical noise. The RS-422 format uses a
balanced pair of wires for transmission, and another pair for reception. The balanced
pair allows the data to be less susceptible to noise, and RS-422 signals can be sent up
to 2000 feet. The final standard, RS-485, is similar to RS-422 except that a single
pair of conductors is used for both transmitting and receiving data. This makes RS-
485 very attractive for network applications, where data is being shared between
more than 2 devices. A typical application might be an HVAC system that
communicates to various thermostats and to a control system over an RS-485 LAN.
The Crestron C2IR-8 plug-in control card can only transmit RS-232 one-way. The
C2COM-2 plug-in control card is capable of generating RS-232, RS-422 or RS-485
two-way signals. The ST-COM network device can generate RS-232, RS-422, or
RS-485 two-way communication data.
Crestron RS-232, RS-422, and RS-485 Equipment
C2IR-8
The C2-IR8 includes eight serial ports for one-way RS-232.
C2COM-2
The C2COM-2 is a Cresnet plug-in control card. It includes two bi-directional RS-
232/RS-422 (DB-9) ports with hardware handshaking.
CAUTION: The DB9 pin-outs on the C2COM-2 control card are not standard RS-
232. Connecting a straight-through serial cable may damage equipment. Refer to the
Crestron Cable database or contact Crestron for serial cable pin-out specifications.
ST-COM
The ST-COM network device can generate either RS-232, RS-422, or RS-485 data.
Limitations
RS-232 is limited to a wire length of 50ft (15 m) and a minimum of three conductors
(RXD, TXD, and Ground).
Each piece of equipment requires a specific (protocol) format for the data it is
expecting.
Programmer needs to be familiar with binary, hex, and/or ASCII in order to generate
the correct strings.
MIDI (Musical Instrument Digital Interface)
MIDI stands for Musical Instrument Digital Interface and is yet another serial
communications standard. As its name implies, MIDI is used most commonly for
allowing musical instruments to talk to one another. However, certain audio mixers,
Primer – DOC. 6253 Crestron SIMPL Windows 11