Matrix Orbital GLK19264-7T-1U - Manual (Page 20)

NOTE These delays are consrevative, and may be decreased based on performance
4.1.2 I 2 C Transaction Example
The typical I 2 C transaction contains four parts: the start sequence, addressing, information, and stop
sequence. To begin a transaction the data line, SDA, must toggle from high to low while the clock line, SCL,
is high. Next, the display must be addressed using a one byte hexadecimal value, the default to write to the
unit is 0x50, while read is 0x51. Then information can be sent to the unit; even when reading, a command
must first be sent to let the unit know what type of information it is required to return. After each bit is sent,
the display will issue an ACK or NACK as described above. Finally, when communication is complete, the
transaction is ended by toggling the data line from low to high while the clock line is high. An example of
the use of this algorithm to write a simple “HELLO” message can be seen in 2.
Table 2: I 2 C Transaction Algorithm
START Toggle SDA high to low
Address 0x50
Information 0x48 0x45 0x4C 0x4C 0x4F
STOP Toggle SDA low to high
4.1.3 Serial Communication
In addition to being able to communicate via I 2 C the GLK19264-7T-1U communicates natively through
the RS-232 protocol at at a default baud rate of 19,200 bps and is capable of standard baud rates from 9600
to 115,200 bps. Furthermore the GLK19264-7T-1U is also capable of reproducing any non-standard baud
rate in between using values entered into our baud rate generation algorithm and set through command 164
(0xA4). The display module communicates at standard voltage levels of -30V to +30V or at TTL levels of 0
to +5V by setting the Protocol Select Jumpers to TTL.
4.1.4 USB Communication
The GLK19264-7T-1U is a USB device that offers identical communication protocol as the serial com-
port. capable of communicating via a USB interface. The USB communications are identical to the serial
communications. Communication is via a virtual com port, which is created in the operating system by the
drivers necessary to install the USB display. The GLK19264-7T-1U communicating via USB is capable of
baud rates of 19,200 bps to 115,200 bps. Other baud rates are subject to the limitation of the virtual com port
driver. For further information regarding supported operating systems, and driver limitations please contact
technical support.
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