- 32 -
3. TECHNICAL BRIEF
3.8 Keypad Switches and Scanning
The key switches are metal domes, which make contact between two concentric pads on the keypad
layer of the PCB when pressed. There are 22 switches , connected in a matrix of 5 rows by 5 columns,
as shown in Figure 3-8, except for the power switch (END), which is connected independently.
Functions, the row and column lines of the keypad are connected to ports of AD6726.
The columns are outputs, while the rows are inputs and have pull-up resistors built in. When a key is
pressed, the corresponding row and column are connected together, causing the row input to go low
and generate an interrupt. The columns/rows are then scanned by AD6726 to identify the pressed key.
LGE Internal Use Only
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
Figure 3.8 Keypad Switches and Scanning
CLR
#
1
DOWN
9
RIGHT
PWR
5
6
SEL
*
MENU
4
LEFT
7
UP
0
3
2
SEND
CONF
8
SW405
680
R403
UP
SW403
C415
DNI
C412
DNI
680
R419
CLR
R425
680
RIGHT
SW402
C406
DNI
SEND
SW401
SHARP
DNI
C416
SW407
R406
680
C405
DNI
C407
R427
680
DNI
R424
680
C413
DNI
680
R426
END
SW409
LEFT
CONF
SW408
SW404
SEL
ICVN0505X150FR
VA403
R405
680
STAR
R422
680
DNI
C411
680
R404
R400
680
C410
DNI
DOWN
SW400
MENU
SW406
KEY_ROW3
KEY_ROW2
KEY_ROW1
KEY_ROW0
KEY_ROW4
KEY_COL4
KEY_COL3
KEY_COL2
KEY_COL1
KEY_COL0
POWERKEY
Summary of Contents for KP175
Page 135: ...Note ...