Table of Contents
Advertisement
3.10 Keypad Switches and Key Backlight Illumination
(1) Keypad Switches
The key switches are metal domes, which make contact between two concentric pads on
the keypad layer of the PCB when pressed. There are 21 switches (KB500-KB522),
connected in a matrix of 5 rows by 5 columns, as shown in Figure, except for the power
switch (KB500), 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.
KB500
POWERKEY
$V
END
$V
KEYROW0
KEYROW1
KEYROW2
KEYROW3
KEYROW4
KEYCOL0
KEYCOL1
KEYCOL2
KEYCOL3
KEYCOL4
R506
$V
680
R507
$V
$V
680
R508
$V
$V
680
R509
$V
$V
680
R510
$V
$V
680
R511
680
$V
R512
680
$V
R513
680
$V
R514
680
$V
R515
680
$V
Figure 3-15 Circuit Diagram of Keypad Switches
KB502
KB503
$V
$V 2
1
$V
$V
KB507
KB508
$V 4
$V 5
$V
$V
KB512
KB513
$V 7
$V 8
$V
$V
KB517
KB518
$V
$V 0
*
$V
$V
- 29 -
3. TECHNICAL BRIEF
KB501
$V
CLR
KB504
KB505
$V 3
$V
LEFT
$V
$V
KB509
KB510
$V 6
$V
UP
$V
$V
KB514
KB515
$V 9
$V
RIGHT
$V
$V
KB519
KB520
$V #
$V
DOWN
$V
$V
KB506
$V
MENU
KB511
$V
SELECT
KB516
$V
SEND
KB521
$V
CONFIRM
Advertisement
Table of Contents
