C8051F980-C-GM Datasheet, PDF (102/325 Pages) Silicon Laboratories – Ultra Low Power, 8-2 kB Flash, Capacitive Sensing MCU

C8051F99x-C8051F98x
8.4. CS0 Multiple Channel Enable
CS0 has the capability of measuring the total capacitance of multiple channels using a single conversion.
When the multiple channel feature is enabled (CS0MCEN = 1), Channels selected by CS0SCAN0/1 are
internally shorted together and the combined node is selected as the CS0 input. This mode can be used to
detect a capacitance change on multiple channels using a single conversion and is useful for implementing
“wake-on-multiple channels”.
8.5. CS0 Gain Adjustment
The gain of the CS0 circuit can be adjusted in integer increments from 1x to 8x (8x is the default). High
gain gives the best sensitivity and resolution for small capacitors, such as those typically implemented as
touch-sensitive PCB features. To measure larger capacitance values, the gain should be lowered
accordingly. The bits CS0CG[2:0] in register CS0MD set the gain value.
8.6. Wake from Suspend
CS0 has the capability of waking the device from a low power suspend mode upon detection of a “touch”
using the digital comparator. When the CS0SMEN is set to 1, CS0 may also wake up the device after an
end of scan event when CS0CM[2:0] are set to 101b or after each conversion when CS0CM[2:0] are set to
110b or 111b. If the accumulate feature is enabled, the device wakes up after all samples have been
accumulated. The CS0WOI bit in the CS0MD1 register can be used to configure desire wake from
suspend behavior.
8.7. Using CS0 in Applications that Utilize Sleep Mode
To achieve maximum power efficiency, CS0 should be enabled only when taking a conversion and dis-
abled at all other times. CS0 must be disabled by software prior to entering Sleep Mode.
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