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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 15 switches (Normal Key 12EA, Volume up down side key,
camera side key), connected in a matrix of 5 rows by 3 columns, as shown in Figure 3-11, which is
connected independently. Functions, the row and column lines of the keypad are connected to ports of
AD6721. 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 AD6721 to identify the
pressed key.
LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
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