Theory of Operation: Controller 3-51
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 3-36. 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 Ta bl e
3-9. 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 3-36. Keypad Interface Outline
Table 3-9. 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
*FPC = Flexible Printed Circuit
OMAP
ROW
COLUMN
KEYPAD FPC
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