Gilderfluke&Co 8 Bit Digital Audio Systems - Manual (Page 33)

- AB-100 AudioBrick Serial Port Commands -
The MACs digital audio system can be controlled by simple switch clo-
sures to start and stop playback or looping, mute the audio, and perform a
variety of functions. Besides this method of controlling the Repeater cards,
you can talk to any or all the cards at one time through a serial data line
from your computer, terminal, or control system.
All commands sent to the MACs digital audio system through its serial in-
terface take the following format. All characters are sent in ASCII. All numer-
ic 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 digital audio system receives another command
while it is waiting for additional input needed 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 sys-
tem is shown in outline . The response to a command is shown in italics .
If the digital audio system is in a mode where you expect to receive
some response from it (generally in one of the echo modes), you must wait
to receive all the characters you are expecting before sending the system a
new command. The reason for this is that you are actually talking to up to
256 microprocessors at a time. If you issue a command that gives a respon-
se from one card, and then a command that gives a response from a sec-
ond card 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 digital audio system with too many
commands through the serial port. You don't want to take too much time
away from the Digital Audio Repeater to serve the serial port.
If you are using a computer as a terminal you will need to run a modem
or terminal emulation program. These will send everything you type on the
keyboard out the serial port on your computer while printing on the screen
anything that comes in from the audio system through the serial port. A
modem program will usually have the advantage over a terminal emula-
tion 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 digital
audio system uses no screen control codes or ESCape 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. Higher or lower baud rates
can be used if you configure the Digital Audio RepeatersÕ serial port to run
at a different speed. You should set your program not to insert an extra
LineFeed (LF) character after each Carriage Return (CR) it receives. If you
are going to be downloading configuration strings to the system (command
ÔsÕ), you will also need to tell the modem program to put a slight delay be-
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