Matrix Orbital GTT70A - Manual (Page 5)

1 Command Summary
1 Introduction
1.1 Communication
Settings
The multiple communication protocols available and simple command structure of the GTT mean that a
variety of applications can be used to communicate with the display. Basic default settings for serial
protocols, including USB, TTL, RS232, and RS422, as well as I
2 C are shown below.
Table 1: Serial Communication Settings
Speed Data Bits Parity Stop Bits Flow Control
115.2Kbps 8 None 1 Hardware
Table 2: I
2
C Communication Settings
Write Read Speed
80
d
81
d
Up to 400KHz
Transmission
By default, all bytes sent to the display are printed using the default font and standard ASCII encoding.
For example, if the user sends the decimal value 65 to the display, an upper case ‘A’ will appear on the
display. The module also responds to a few ASCII control characters. The functionality of these
characters can be toggled between Windows and UNIX compatibility modes using the Control Character
Mode command. The default behavior is Unix mode.
Table 3: Control Characters
UNIX Compatibility Mode Windows Compatibility Mode
7 The bell character will signal the Default Beep The bell character will signal the Default Beep
10 Move the text insertion point to the beginning of the
next line down
Move the text insertion point down one line
13 Move the text insertion point to the beginning of the
next line down
Move the text insertion point back to the beginning of
the current line
Finally, when the display detects the command prefix character 254, it will enter a command processing
state and await the command number and its parameters. Multiple bytes are transferred in Big Endian
format. Once the command is finished, the display will automatically return to displaying all bytes sent.
Return Messages
When the display must return data to the host, it will use a standard message format. Each message will
begin with the return message prefix 252, followed by the command number generating the message, a
short value containing the length of the data in the message, and finally the data in the message.
Table 4: Example Return Message
Prefix Message ID Length Data
252 47 0 3 255 255 255
The sample above shows the expected return values from the Get Font Colour command. In this
manual, expected return messages are described below any required parameters.