Theory of Operation: Controller 3-57
3.2.6.4 Keypad
The Dual Display Model contains a 21 button keypad, which translates to a 5x5 row and column
keypad matrix as shown in Figure 3-46. The keypad also contains LEDs for the backlighting of the
keys, which is described in more detail in Section 3.2.6.3: "Intelligent Lighting". Every key is assigned
a particular row and column to identify the unique key, as shown in keypad mapping Table 3-8. The
keypad flex also contains 2, 6-channel filters that each row and column signal passes through. Each
row of the keypad contains an external pull-up resistor, and all the rows are interrupt based inputs to
OMAP. The columns are driven low by default in OMAP. When a key is pressed, the corresponding
key row and column are shorted together and causes a low level to be input on the corresponding
row in OMAP. Upon receiving the row interrupt, the OMAP IC is then programmed to scan the
column output to determine which corresponding column was selected that generated the interrupt.
Figure 3-46. Keypad Interface Outline
Table 3-8. Key Map Matrix
Key Row, Column Map Key Row, Column Map
{ 0 , 4 3 3 , 2
| 1 , 4 4 2 , 0
} 2 , 4 5 2 , 1
H 4 , 0 6 2 , 2
< 4 , 1 7 1 , 0
U 0 , 3 8 1 , 1
D 4 , 2 9 1 , 2
> 1 , 3 * 0 , 0
P 2 , 3 0 0 , 1
*FPC = Flexible Printed Circuit
OMAP
ROW
COLUMN
KEYPAD FPC
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