Global Cache GC-IRE Installation Manual

Quick Start Guide

Global Caché

GC-IRE

IR Extender

Overview. The GC-IRE IR Extender is a new concept in automated controls that
allows IR devices, such as remote controllers, to act as digital input devices in a
networked environment. The GC-IRE digitizes IR inputs from a Global Caché,
Xantech, or SpeakerCraft IR receiver or distribution block. By converting this IR
information to serial ASCII text, IR can now be considered a new input method for
digitally controlled installations.

The GC-IRE has two interfaces, a 3.5mm stereo jack for IR input and a serial
RS232 male DB9 connector for ASCII text output. The serial connection provides
both power (no external power supply is required) and two-way communication for
GC-IRE configuration and IR output. Additionally, an IR noise measurement mode
is available to assist in proper placement of IR receivers to minimize background
IR interference. The GC-IRE samples IR input including background noise and
modulation frequency. It then attempts to filter out incomplete IR commands,
background noise, and incorrect IR patterns before transmitting good IR commands
as serial ASCII text.

Getting Started. A simple method to become familiar with the GC-IRE is to
connect it to the PC's RS232 serial port and send commands using Windows Hyper
Terminal. Hyper Terminal can be found under
Programs/Accessories/Communications in the PC's Start menu. After selecting
Hyper Terminal, enter a name such as, PC_9600 and click OK. When prompted
with “Connect using,” select COM1, not TCP/IP. In the next window; for “bits per
second” select 9600; for “data bits” select 8; for “parity” select none; for “stop bits”
select 1; and for “flow control” select none. Now click OK to complete your Hyper
Terminal setup.

Plug the GC-IRE into the PC's COM1 serial port. Since power is supplied by the
RTS line (pin 7), flow control (handshaking) must be disabled for proper operation.
At power up, the ACT indicator will blink once and then remain on. This indicator
will also blink when receiving IR signals, to indicate IR activity. Type gv↵ in the
Hyper Terminal window to obtain the version number of the GC-IRE.

The GC-IRE is ready to receive IR information. Plug in a Global Caché IR receiver
(GC-RF1 or GC-RG1) or a GC-CXG from a Xantech and SpeakerCraft IR
installation to the "IR IN" 3.5mm stereo jack. As IR is received the ACT indicator
will blink and the IR digitized output will be sent to the open Hyper Terminal
window.

IR Encoding and Transmission. The GC-IRE transmits IR signals in real time as
comma delimited ASCII text terminated by a carriage return (↵). Other terminators
may be used, see command set. An IR signal is a sequence of ON and OFF states
modulated with a carrier frequency ( ƒ ) during the ON state. Most IR remote
control devices operate at frequencies near 40KHz with some devices operating up
to 500KHz. The ON and OFF timing is measured in periods (τ) of the carrier
frequency, where τ = 1/ƒ. For example, an ON state of 24 represents 600µS for a
carrier frequency of 40KHz, (600µS = 24 / 40,000Hz).

ON

OFF OFF

ON

ON

The GC-IRE employs a compression scheme to reduce serial data for better
performance. Uncompressed IR signals are represented in the following manner as
shown below.

GC-IRE,<frequency>,<ON1>,<OFF1>,<ON2>,<OFF2>,…,<ONn>,<OFFn>↵

where;

<frequency> is /32000/33000/…/500000/ hertz

<ONx> is /2/3/…/65635/ carrier frequency periods

<OFFx> is /2/3/…/65635/ carrier frequency periods

↵ is 0x0D Hex ASCII carriage return

The following is an uncompressed ASCII text string representing a typical IR
remote control signal. Alternating ON/OFF pairs are highlighted to improve
readability.

GC-IRE,55000,22,340,24,156,24,158,23,92,23,157,23,157,23,92,23,156,23,156,

23,157,23,157,23,156,23,310,23,311,23,156,24,156,23,157,23,1100↵

The IR signal has a 55000Hz (55KHz) carrier frequency, with its first ON state of
22 periods or 400µsec. The following OFF state is 340 periods or 6.182mS in
duration. The final 1100 OFF actually may be longer, but after 20mS of inactivity
the GC-IRE considers the IR signal to be finished. The 20mS value can be changed
to suit special installation needs, see IRend commands below. Typically, 20mS is
sufficient time between IR commands to avoid misinterpreting back-to-back
commands as one long command. Most remote controls repeatedly send IR
commands when the button is held down inserting a pause between each command.
The GC-IRE always encodes commands as separate commands if this pause is
greater than the IRend setting. Otherwise, commands are concatenated into one
long command. The GC-IRE adds a final OFF pulse equal to the IRend setting at
the end of each IR command. The last OFF is calculated as IRend * ƒ, where IRend
is in seconds.

Some IR remote controllers will send continuous back-to-back IR commands for
volume control and fast-forwarding of media. In rare circumstances, a continuous
IR command may overflow the GC-IRE's internal buffer. To indicate an overflow,
the current serial IR transmission is halted and truncated with an ASCII X. All IR
activity must stop for IRend seconds before a new IR signal will be transmitted.

To further reduce the likelihood of buffer overflow, all IR serial data is compressed.
The GC-IRE takes advantage of the fact that many ON/OFF pairs are repeated
several times within an IR command. By representing a repeated ON/OFF pair with
a single upper-case letter A, B, C, or D, IR serial data can be reduced up to one
third of its original size. The compression process works by assigning an A to
represent the first pair in a new IR signal, B to the next different pair, and so on.
Using compression, the first occurrence of an ON/OFF pair is transmitted as before,
with all subsequent repeats of that pair represented by its assigned single letter. To
aid compression, ON/OFF values are considered equivalent if they are within three

counts of each other, minimizing the effects of noise and round-off errors. The
previous IR command is compressed as shown below. Letters A thru D are
assigned as follows: A = ,22,340; B = ,24,156; C = ,23,92; and D = ,23,310.
Remembering that ON/OFF values can be within three counts of the assigned
valued above, the original IR command will compress to the following.

GC-IRE,55000,22,340,24,156B,23,92BBCBBBBB,23,310DBBB,23,1100↵

Since the first pair 22,340 never repeats, the letter A is not used. Additionally, if
the last pair 23,1100 had repeated, it would be sent uncompressed since all four
letters are assigned to other pair values. Finally the letters are sent without comma
delimiters reducing the original signal from 138 to just 61 characters.

IR Noise Filtering. The GC-IRE contains filtering to improve performance by
removing false IR signals occurring from direct sunlight and fluorescent lights.
Incomplete IR signals are also caused by remote controllers operated from too great
a distance, partially blocked, pointed poorly, or in need of fresh batteries. The GC­IRE filtering is not intended to correct a corrupted IR signal, but to prevent it from
being transmitted out as serial data. However, when an IR signal becomes
corrupted during its transmission, the GC-IRE transmission is halted and truncated
with an ASCII Z.

Noise Measurement. Included in the GC-IRE is the ability to measure background
IR noise. By enabling the noise meter ( ny↵ ) through Hyper Terminal, continuous
data values (from 0 to 100%) are transmitted serially indicating the amount IR
signals received within the sample period. This is helpful when placing an IR
receiver near fluorescent lights or plasma TVs. By optimizing IR receiver
placement, unwanted noise can be minimized or avoided completely. With
placement complete, the noise meter is disabled ( ny↵ ) and IR remote control
commands can be sent.

String Terminators. The terminators used for data transmitted from the GC-IRE
may be changed to better suit the software environment in which the GC-IRE is
being used. For example, it may be more effective to use a carriage return, line
feed for a UNIX/Linux system, and a NULL for a system employing Flash or other
software requiring NULL terminated strings.

Command Summary

Cmds Definition Response Stored Action

gv↵ get version ver,x.x.x ⇐ - where x is a number

id↵ identity of device device,GC-IRE⇐ - -

gs↵ get state IRend,<X>msec⇐ - where <X> is
|20|35|50|100|

GC-IRE Settings

Cmds Definition Response Stored Action

tc↵ CR terminator - yes send 0x0D hex

tl↵ CR LF terminator - yes send 0x0D 0x0A hex

tn↵ NULL terminator - yes send 0x00 hex

Cmds Definition Response Stored Action

e1↵ change IR end IRend=20msec⇐ yes sets IR end to 20msec

e2↵ change IR end IRend=35msec⇐ yes sets IR end to 35msec

e3↵ change IR end IRend=50msec⇐ yes sets IR end to 50msec

e4↵ change IR end IRend=100msec⇐ yes sets IR end to 100msec

ny↵ noise meter yes - no enable noise meter

nn↵ noise meter no - no disable noise meter

Special Responses

Cmds Definition Response Stored Action

- - unknowncommand⇐ - received invalid cmd

- - X⇐ - indicates buffer
overflow

- - Z⇐ - invalid IR signal

Specifications

Serial Interface

Encoding Comma delimited ASCII text ending with a

terminator

Connector Female DB-9, DTE format

RTS, pin 7 – used for power

Gnd, pin 5 – signal and power ground

TxD, pin 3 – transmit data to the GC-IRE

RxD, pin 2 – received data from the GC-IRE

Baud rate 9600

Other No parity, one stop bit

Flow Control none

Power Supplied by RTS (pin 7), must be 7 to 25 volts @
5mA

IR Sensor interface

Connector type 3.5mm stereo jack

IR frequency range 30 to 500KHz

Power supplied 7 to 25 volts @ 2mA

Global Caché, Inc.
160 East California Street, PO Box 1659
Jacksonville, Oregon 97530
Phone [phone]
Fax [phone]
www.globalcache.com
Support: [e-mail]
Sales: [e-mail]

PN: 040504-01 ver 3/Information subject to change without notice.

Copyright ©2007 Global Caché, Inc. All rights reserved.