Keypad Switches And Scanning - LG C1150 Service Manual
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3. TECHNICAL BRIEF
3. 9 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 24 switches (SW1-SW2,KB2~KB22),
connected in a matrix of 5 rows by 5 columns, as shown in Figure, except for the power switch
(KB101), which is connected independently. Functions, the row and column lines of the keypad
are connected to ports of AD6525. 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 AD6525
to identify the pressed key.
KEY_ROW0
KEY_ROW1
KEY_ROW2
KEY_ROW3
KEY_ROW4
KEY_COL0
KEY_COL1
KEY_COL2
KEY_COL3
KEY_COL4
SW1
SW2
DOWN
UP
4
1
4
1
5
3
2
5
3
2
VA201
VA202
R224
R225
R228
R229
680
680
680
680
KB4
KB20
1
2
SP204
SP205
SP206
KB5
KB21
5
4
SP209
SP211
SP212
KB6
KB2
7
8
SP227
SP228
SP229
KB7
KB3
0
*
SP231
SP232
SP233
Figure 3-23. C1150 KEYPAD CIRCUIT
- 42 -
KB22
CLR
SP201
KB16
KB9
KB8
3
LEFT
MENU
SP207
SP208
KB17
KB10
KB13
6
UP
SELECT
SP210
SP213
KB18
KB11
KB14
9
RIGHT
SEND
SP226
SP230
KB19
KB12
KB15
#
DOWN
CONFIRM
SP234
SP235
R240
R241
680
680
VBAT
R107
10K
R110
KEYON
KB101
1K
PWR KEY
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