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 3.
Table 3: 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 LK202-25 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 LK202-25 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.
4.2
Changing the I
2
C Slave Address
Syntax
Hexadecimal
0xFE 0x33 [adr]
Decimal
254 51 [adr]
ASCII
254 “3” [adr]
Parameters
Parameter
Length
Description
adr
1
The new I
2
C write address (0x00 -
0xFF).
Matrix Orbital
LK202-25
18
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