Keypad Switch And Scanning - LG KG245 Service Manual

3.9 Keypad Switch 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 (Normal Key 24EA, Camera side key, Volume up down side key),
connected in a matrix of 5 rows by 5 columns and additional GPIO 35 for KEY_ROW5, as shown in Figure 3-
24, except for the power switch (KB1), which is connected independently. Functions, the row and column
lines of the keypad are connected to ports of AD6527. 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 AD6527 to identify the pressed
key.
POWERKEY
R302
KEY_ROW0
KEY_ROW1
KEY_ROW2
KEY_ROW3
KEY_ROW4
KEY_ROW5
KEY_COL0
KEY_COL1
KEY_COL2
KEY_COL3
KEY_COL4
VBAT
CAMERA
CN602
1
2
R301
3
10K SW306
4
5
680
END
R318
100
R322 680
R323 680
R324 680
R331 680
R332 680
R333 680
R343 680
R349 680
R352 680
R354
680
R356 680
S71PL256NC0_TLA084
Figure 3-24. Keypad Switches and Scanning
- 41 -
3. TECHNICAL BRIEF
VOL_UP VOL_DOWN
R321
R319 R320
CLR
100 100 100
SW307
1 2 3
SW309 SW310 SW311 SW312
SW314 SW315 SW316 SW317
4 5 6
SW319 SW320 SW321 SW322
7 8 9
SW324 SW325 SW326 SW327
* 0 #
SW329
T
Side Key
FAV
SW308
LEFT
SW313
MENU
SW318
UP
SEL
SW323
RIGHT
SEND
SW328
DOWN
CONF