Matrix Orbital LK162-12 Legacy - Manual (Page 16)

LK162-12 rev 4 16
4. Keypad Interface
This chapter describes the keypad interface and associated commands in detail.
4.1 General
The LK162-12 keypad interface processes the keypad row/column matrix into a serial (RS-232 or I 2 C) data
byte stream. Aside from this processing, the keypad has no effect on the LK162-12 display. If you need to
send keystrokes to the display, they must be routed through your controller. Whenever a columns and a row
pin are shorted together, a keystroke will be generated and either held in the buffer (I
2 C) or send over the
serial line to the host (RS-232). The keypad shares the same pins as the seven GPOs on the LK162-12 and
only one or the other can be used at one time.
4.2 Connections
Figure 4-1 Keypad Connector
The connector is not "keyed" so your keypad will probably plug in either of two ways. The LK162-12 will
not be damaged by reversing the connector, but your keypad will generate a different ASCII character
mapping for each position. If your connector has fewer than 7 pins it should be centered on the LK162-12
connector, starting with Row 3 and Column 1 and going out. Any matrix style keypad will work with the
LK162-12, as well, momentary switches.
The returned key codes are as follows, but note that your keypad may be laid out in a different pattern. If
this is the case, you will need to interpret the key codes differently. The diagram 1 shows the logical layout
(row 1, column 1 in upper left). The connector for the keypad is a 10 pin 0.1" spacing male header. Pin 1 is
indicated in Figure 2-1. Pins 1 through 5 are columns and pins 6 through 10 are rows. The keypad is
scanned whenever a key is pressed: there is no continuous key scan. This means that key presses are dealt
with immediately without any appreciable latency. This also prevents electrical noise which is often caused
by continuous key scans.