VK202-25 rev. 05
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4. Keypad Interface
This chapter describes the keypad interface and associated commands in detail.
4.1 General
The VK202-25 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 VK202-25 display. If you need to
send keystrokes to the display, they must be routed through your controller.
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 VK202-25 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 10 pins it should be centered on the VK202-25
connector.
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.
Columns
1 2 3 4 5
1 A B C D E
2 F G H I J
3 K L M N O
4 P Q R S T
Rows
5 U V W X Y
Note:
The keypad connector must be wired with columns on one side and rows on the other side of the
center of the connector. If your keypad isn't wired this way you will need to make an adapter or rewire the
connector to meet this requirement.
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