Silicon Laboratories EFR32xG14 Wireless Gecko Reference Manual page 948

28.3.16.2 LC Sensor
Figure 28.16 LC Sensor Setup on page 948
LESENSE can be used to excite and measure the damping factor in LC sensor oscillations. To measure the damping factor, the ACMP
can be used to generate a high output each time the sensor voltage exceeds a certain level. These pulses are counted using an asyn-
chronous counter and compared with the threshold in COMPTHRES in the CHx_EVAL register. If the number of pulses exceeds the
threshold level, the sensor is said to be active, otherwise it is inactive.
how the output pulses from the ACMP correspond to damping of the oscillations. The results from sensor evaluation can automatically
be fed into the decoder in order to keep track of rotations.
LC sensor ACMP output
2,95
2,45
1,95
1,45
0,95
0,45
-0,05
0 10 20 30 40
The following steps show how to configure LESENSE to scan through the four LC sensors 100 times per second.
1. Assuming LFACLK
LESENSE
100Hz.
2. Enable the VDAC and configure it to produce a voltage of Vdd/2.
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below illustrates how the EFR32 can be set up to monitor four LC sensors.
DAC0_OUT0
ACMP0_CH0
ACMP0_CH1
ACMP0_CH2
ACMP0_CH3
Figure 28.16. LC Sensor Setup
ACMP threshold
50 60 70 80 90
Figure 28.17. LC Sensor Oscillations
is 32kHz, set PCPRESC to 3 and PCTOP to 39 in CTRL. This will set the LESENSE scan frequency to
LESENSE - Low Energy Sensor Interface
Figure 28.17 LC Sensor Oscillations on page 948
LC sensor ACMP output
2,95
2,45
1,95
1,45
0,95
0,45
-0,05
100 0 10 20 30
Reference Manual
X X
X X
ACMP threshold
40 50 60 70 80
Rev. 1.1 | 948
illustrates
90 100