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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 27 switches (Normal Key 24EA, Torch 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.
VBAT
R372
10K
SW305
POWERKEY
R300
680
KEY_ROW0
KEY_ROW1
KEY_ROW2
KEY_ROW3
KEY_ROW4
KEY_ROW5
KEY_COL0
KEY_COL1
KEY_COL2
KEY_COL3
KEY_COL4
Figure 3-27. Keypad Switches and Scanning
TORCH
SW300
END
R302
100
R373
680
R386
680
R375
680
R376
680
R377
680
R378
680
R379
680
R380
680
R381
680
R382
680
R383
680
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3. TECHNICAL BRIEF
VOL_UP
VOL_DOWN
SW301
SW302
SW304
R301
R303
R305
100
100
100
1
2
SW308
SW309
SW310
SW313
SW314
SW315
4
5
SW318
SW319
SW320
7
8
SW323
SW324
SW325
*
0
SW328
T
SW303
R304
CLR
FAV
100
SW306
SW307
3
LEFT
SW311
SW312
MENU
SW316
SW317
6
UP
SEL
SW321
SW322
9
RIGHT
SEND
SW326
SW327
#
DOWN
CONF
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