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3.7 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 26 switches (Normal Key 24EA, Volume up down side key),
connected in a matrix of 5 rows by 5 columns, as shown in Figure 3-7, except for the power switch
(SW300), which is connected independently. Functions, the row and column lines of the keypad are
connected to ports of AD6724. The columns are outputs, while the rows are inputs and have pullup
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
AD67240 to identify the pressed key.
VBAT
R300
10K
R314
POWERKEY
680
R316
KEY_ROW0
R318
KEY_ROW1
R319
KEY_ROW2
R320
KEY_ROW3
R321
KEY_ROW4
R324
KEY_COL0
R325
KEY_COL1
R326
KEY_COL2
R327
KEY_COL3
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
KEY MATRIX
C300
END KEY
NA
SW300
T
SW302
680
C307
1
NA
SW306
680
C309
4
NA
SW309
680
C310
7
NA
SW314
680
C313
*
NA
SW319
680
C315
NA
680
680
680
680
C321
NA
Figure 3.7 Keypad Switches and Scanning
3. TECHNICAL BRIEF
CN300
C301
C302
NA
NA
SEND_KEY
2
3
CLR
SW303
SW304
SW305
LEFT
SW307
5
6
UP
SW310
SW311
SW312
DOWN
CONF
RIGHT
SW315
SW316
SW317
0
8
#
SW320
SW321
SW322
C322
C323
C324
NA
NA
NA
- 31 -
2V8_VEXT
R301
10K
SEND
R315
680
SW301
C306
NA
MENU
SW308
SEL
SW313
FAV
SW318
9
SW323
LGE Internal Use Only
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