4.1.12 Active Mode and Sleep Mode Transitions

Capacitive sensing inputs will stay in active mode until no inputs detect qualified touches for a span of time defined by the counts until

sleep parameter stored in the configuration profile. The scan period of enabled inputs is defined by the active mode scan period, also

found in the configuration profile. If free run mode is enabled, the active mode sensing engine will remain awake and scanning the sen-

sors as fast as possible. If free run mode is disabled, the engine will put itself into a low power state for the remainder of the active

mode scan period, after a scan has completed.

When in sleep mode, the sensing engine will wake at a period defined by sleep mode scan period to do a scan on sensors that have

been enabled as wakeup sources. If the engine finds a candidate touch in this state, the system reverts to active mode to continue

scanning.

Note that in systems where a proximity input is selected, the sleep mode scan engine uses conversions on the proximity input instead

of sensors enabled as wakeup sources.

qualified touch

release

touch release

new touch

no touch

counter = 1

no touch

counter = 2

...

no touch counter

= counts before

sleep

device enters

sleep

sleep scan sees

touch, wakes,

qualifies touch

no touch

counter = 0

t

Figure 4.4. Active and Sleep Transitions

CPT112S Data Sheet

Functional Description

silabs.com | Smart. Connected. Energy-friendly.

Preliminary Rev. 0.1 | 16