Gilderfluke&Co PA System - Manual (Page 9)

Serial Port Connections and Communications:
The Intelligent PA System is communicated with a serial data line from your computer, terminal, or
control system. As the master for the audio system, it acts a a bridge for all communications with all
Digital Audio Repeaters, Smart Brick Systems, and anything else attached to it.
All characters are sent to the PA System in standard ASCII. All numeric values are sent in
HEXadecimal (HEX for short), and consist of one or more ASCII characters (0-9, A through F). The case
(as in upper and lower) of all input is important. A lower case 'a' signifies a command, while an 'A' is a
numeric value. If the PA System receives another command while it is waiting for additional input need-
ed to complete the previous command, it will abandon the previous command and start working on the
new one.
In the following documentation any input you will send to the audio system is shown in outline. The
response to a command is shown in italics.
If the PA System is in a mode where you expect to receive some response from it, you must wait to
receive all of the characters you are expecting before sending the system a new command. The reason
for this is that you are potentially talking to hundreds of microprocessors at a time, and if you issue a
command which gives a response from one, and then a command which gives a response from a an-
other before the first has finished, then the two may try to output data at the same time. This won't
cause any damage, but may result in garbled data at the receiver.
It is also possible to overload the PA System with too many commands through the serial port. You
don't want to take too much time away from it to service the serial port.
To communicate with the PA System through the serial port, you can use just about any computer or
terminal which has a serial port on it. Some newer computer designs, like the Apple Macintosh, come
with serial ports which are directly compatible with the RS-422 / RS-485 signal levels the PA System wants
to see. These signal levels are close enough to be used with the RS-232 signal levels found on most
older computers (like most IBM compatibles) with only a simple adapter cable, so long as the wire isn't
too long. To gain the full advantage of the RS-422 / RS-485 signal levels you will need to use a signal
level adapter.
If you are using a computer as a terminal you will need to run a modem or terminal emulation pro-
gram. These will send everything you type on the keyboard out the serial port on your computer while
printing on the screen anything which comes in from the audio system through the serial port. A modem
program will usually have the advantage over a terminal emulation program in that it will allow you to
save data to your computer's disk drives and then send it back to the audio system at a later date. The
PA System uses no screen control codes or <ESC>ape sequences, so it should work on any machine
with a 80 column by 24 line display. Machines with other display formats will work, but may not look so
neat on the screen.
When configuring your modem program, you should set it for 9600 baud, 8 data bits, one stop bit,
and no parity. You must set your program not to insert an extra LineFeed (LF) character after each
Carriage Return (CR) it receives.
If you have hooked up the PA System to your computer and it still doesnÕt seem to respond to the
keyboard, the first thing to check is that you are attached to the right serial port on the PC. The easiest
way to do this is to disconnect the PA System and short between the Tx data out and Rx data in pins on
the serial port connector on the back of your computer. On all IBMs and compatibles this means sticking
a paper clip or similar object between pins 2 and 3 on the ÔCom.Õ connector. While still running the
modem program, anything you type should be shown on the screen while this paper clip is in place,
while nothing will appear when you remove it. If your computer passes this test, then you are using the
right serial port and the problem is most likely the baud rate setting or in your wiring to the PA System. If
you get characters on the screen even with the paper clip removed from the serial port, it means you
probably need to set the ÔechoÕ mode to ÔnoneÕ or Ôfull duplexÕ and try this test again.
The serial data signals from the PA System are brought out on the connector labeled 'TERMINAL
Input'. This is a 6 position RJ-11 (modular telephone style connector). Facing the end of the cable with
the release latch upwards, its pin out is as follows:
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