Keypad Switches And Scanning - LG KG110 Service Manual

LCD CONNECTER
9
_LCD_RESET
8
DATA0
7
DATA1
6
DATA2
DATA3
DATA4
DATA5
DATA6
9
DATA7
8
ADD1
7
_LCD_CS
6
_WR
DATA8
DATA9
DATA10
DATA11
9
DATA12
8
DATA13
7
DATA14
6
DATA15

3.3.5 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 21 switches, connected in a matrix of
5 rows by 5 columns and additional GPIO 35 for KEY_ROW5, as shown in Figure 3-x,
except for the power switch (KB1), which is connected independently. Functions, the row
and column lines of the keypad are connected to ports of AD6720. 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 AD6720 to identify the
pressed key.
FL302
ICVE21054E250R401FR
1
INPUT_B1 INPUT_A1
2
INPUT_B2 INPUT_A2
3
INPUT_B3 INPUT_A3
4
INPUT_B4 INPUT_A4
4
INPUT_A4 INPUT_B4
3
INPUT_A3 INPUT_B3
2
INPUT_A2 INPUT_B2
1
INPUT_A1 INPUT_B1
ICVE21054E250R401FR1
FL302 FL303
ICVE21054E250R401FR2
1
INPUT_B1 INPUT_A1
2
INPUT_B2 INPUT_A2
3
INPUT_B3 INPUT_A3
4
INPUT_B4 INPUT_A4
FL302
ICVE21054E250R401FR3
9
INPUT_B1 INPUT_A1
8
INPUT_B2 INPUT_A2
7
INPUT_B3 INPUT_A3
6
INPUT_B4 INPUT_A4
FL302
ICVE21054E250R401FR4
1
INPUT_B1 INPUT_A1
2
INPUT_B2 INPUT_A2
3
INPUT_B3 INPUT_A3
4
INPUT_B4 INPUT_A4
Figure 3-7: LCD Interface Circuit
VMEM
6
7
8
9
LCD_LED_CTL
R302
LIGHT2
LIGHT1
R303
1
_RD
2
3
4
LCD_ID
21
3. TECHNICAL BRIEF
VMEM
R301
51K
1
2
3
4
5
6
7
8
9
10
11
12
13
56 14
15
16
R343
56
17
18
0
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
R304 51K
40
41
CN301
CN301