Matrix Orbital LK402-25 Legacy - Manual (Page 11)

WARNINGS
• Do not apply any power with reversed polarization.
• Do not apply any voltage other than the specified voltage.
2.3 Protocol Select Jumpers
The Protocol Select Jumpers, pictured below in figure 12 , 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 solder jumps on the 232 jumpers. In order to place the display module in I 2 C mode you must first
remove the solder jumps from the 232 jumpers and then place them on 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 12: Protocol Select Jumpers
2.4 General Purpose Outputs
A unique feature of the LK402-25 is the ability to control relays and other external devices using a
General Purpose Output, which can provide up to 20 mA of current and +5Vdc from the positive side of
the GPO. This is limited by a 240 ohm resistor which is located to the above right of the GPOs as pictured
below in
figure 16 . If the device, which is being driven by a GPO, requires a relatively high current (such as
a relay) and has an internal resistance of its own greater than 250 ohms, then the 240 ohm resistor may be
removed and replaced with a Jumper.
- GND
+ MAX: 20 mA, +5Vdc
Figure 13: General Purpose Output
Matrix Orbital LK402-25 7