3. Enable channels 0 through 3 in CHEN. Set IDLECONF for the active channels to DACOUT. The channel pins should be connected
to the VDAC output (effectively shorting the LC sensor) in the idle phase to damp the oscillations.
4. Configure the ACMP to use scaled Vdd as negative input, refer to ACMP chapter for details.
5. Enable and configure PCNT and asynchronous PRS.
6. Configure the GPIOs used as PUSHPULL.
7. Configure the following bit fields in CHx_CONF, for channels 0 through 3:
a. Set EXCLK to AUXHFRCO. AUXHFRCO is needed to achieve short excitation time.
b. Set EXTIME to an appropriate value. Excitation will last for EXTIME/F
AUXHFRCO
seconds.
c. Set EXMODE to HIGH. The LC sensors are excited by pulling the excitation pin high.
d. Set SAMPLE to ACMPCOUNT and COMP to LESS. Status of each sensor is evaluated based on the number of pulses gener-
ated by the ACMP. If they are less than the threshold value, the sensor is said to be active.
e. Set SAMPLEDLY to an appropriate value, each sensor will be measured for SAMPLEDLY/F
LFACLK_LESENSE
seconds.
8. Set CTRTHRESHOLD to an appropriate value. If the sensor is active, the counter value after the measurement phase should be
less than the threshold. If it is inactive, the counter value should be greater than the threshold.
9. Start scan sequence by writing a 1 to START in CMD.
Note:
Exciting the LC sensor by pulling the excitation pin high allows the ESD protection in the pads to clamp any voltage swings below the
ground voltage, giving a consistent starting point for the oscillations.
Reference Manual
LESENSE - Low Energy Sensor Interface
silabs.com
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