Matrix Orbital GLK240128-25 Legacy - Manual (Page 14)

2.3 Protocol Select Jumpers
The Protocol Select Jumpers, pictured below in figure 15 , provide the means necessary to toggle the
display module between RS-232, TTL and I 2 C protocols. As a default, the jumpers are set to RS-232 mode
with zero ohm resistors on the 232 jumpers. In order to place the display module in I 2 C mode you must
first remove the zero ohm resistors from the 232 jumpers and then solder the resistors on to the I2C jumpers.
The display will now be in I
2 C mode and have a default slave address of 0x50 unless it has been changed.
Similarly, in order to change the display to TTL mode, simply remove the zero ohm resistors from the 232
or I
2 C jumpers and solder them to the TTL jumpers.
Figure 15: Protocol Select Jumpers
2.4 Keypad Interface Connector
The GLK240128-25 provides a Keypad Interface Connector which allows for up to a five by five matrix
style keypad to be directly connected to the display module. Key presses are generated when a short is
detected between a row and a column. When a key press is generated a character, which is associated with
the particular key press, is automatically sent on the Tx communication line. If the display module is running
in I
2 C mode, the “Auto Transmit Keypress” function may be turned off, to allow the key presses to remain
in the buffer so that they may be polled. The character that is associated with each key press may also be
altered using the “Assign Key Codes” command, for more detailed information see the Keypad Section, on
page 33.
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