Simultaneous Keypress Detection

Certain applications require the detection of

simultaneous keypresses, such as <SHIFT+KEY> and

<FUNCTION+KEY> combinations. This is done in

software. For instance, the µP detects the SHIFT key is

being pressed. When the µP detects an additional key-

press instead of a key release, it knows the corre-

sponding code is a result of two resistors

in parallel.

Order of Keypress Detection

Some applications require detection of the specific

sequence of keys in software by looking for unique key

presses within 32 ticks (1s). If the duration between

keypresses exceeds the allowed time, assume the key-

press is in error and return to the previous known state.

Power-Up Jack Detect and Keypress

Example

Figure 10 illustrates the FIFO entries during a typical

sequence of events.

Layout, Grounding, and Bypassing

close to the device as possible. Connect GND to a

quiet analog ground plane. Route digital lines away

from SENSE and FORCE.

Wired Remote Controller

___________________________________________________________________________________

13

Figure 10. Software Implemented Hold-Switch Configuration

WIRED REMOTE CONTROLLER

FORCE

HOLD SWITCH