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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 25 switches (Normal Key 22EA, Volume up down and
camera side key, connected in a matrix of 5 rows by 5 columns, as shown in Figure 3-8, except for the
power switch (END), which is connected independently. Functions, the row and column lines of the
keypad are connected to ports of AD6726. 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 AD6726 to identify the pressed key.
LGE Internal Use Only
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
Figure 3.8 Keypad Switches and Scanning
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