EFM32WG Datasheet, PDF (625/834 Pages) List of Unclassifed Manufacturers – The EFM32WG Wonder Gecko is the ideal choice for demanding 8-, 16-, and 32-bit energy sensitive applications.

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less than COMPTHRES, depending on the configuration of COMP. If STRSAMPLE in CHx_EVAL is
set, the counter value or ACMP sample for each channel will be stored in the LESENSE result buffer. If
STRSCANRES in CTRL is set, the result vector, SCANRES, will also be stored in the result buffer. This
will be stored after each scan and will be interleaved with the counter values. The contents of the result
buffer can be read from BUFDATA or from BUF[x]_DATA. When reading from BUF[x]_DATA, neither
the result read pointer or the status flags BUFDATAV, BUFHALFFULL, or BUFFULL will be updated.
When reading through the BUFDATA register, the oldest unread result will be read.
Figure 25.9. Circular result buffer
LESENSE
PTR_WR
BUF0 _D ATA
BUF1 _D ATA
BUF2 _D ATA
BUF3 _D ATA
BUF1 2 _D ATA
BUF1 3 _D ATA
BUF1 4 _D ATA
BUF1 5 _D ATA
PTR_RD
BUFDATA
CH3 result
CH5 result
CH9 result
SCANRES
CH3 result
CH5 result
CH9 result
SCANRES
The right hand side of Figure 25.9 (p. 625) illustrates how the result buffer would be filled when
channels 3,5, and 9 are enabled and have STRSAMPLE in CHx_EVAL set, in addition to STRSCANRES
in CTRL. The measurement result from the three channels will be sequentially written during the scan,
while SCANRES is written to the result buffer upon scan completion.
25.3.8 DAC interface
LESENSE is able to drive the DAC for generation of accurate reference voltages. DAC channels
0 and 1 are individually configured in the PERCTRL register. The conversion mode can be set
to either continuous, sample/hold or sample/off. For further details about these modes, refer to
Section 29.3.1 (p. 705) . Both DAC channels are refreshed prior to each sensor measurement, as
depicted in Figure 25.3 (p. 619) . The conversion data is either taken from the data registers in the
EFM32WG DAC interface (DAC0_CH0DATA and DAC0_CH1DATA) or from the ACMPTHRES bit-
field in the CHx_INTERACT register for the active LESENSE channel. DAC data used is configured in
DACCHxDATA in PERCTRL.
The DAC interface runs on AUXHFRCO and will enable this when it is needed. The DACPRESC bit-field
in PERCTRL is used to prescale the AUXHFRCO to achieve wanted clock frequency for the LESENSE
DAC interface. The frequency should not exceed 500kHz, i.e. DACPRESC has to be set to at least 1.
The prescaler may also be used to tune how long the DAC should drive its outputs in sample/off mode.
Bias configuration, calibration and reference selection is done in the EFM32WG DAC module and
LESENSE will not override these configurations. If a bandgap reference is selected for the DAC, the
DACREF bit in PERCTRL should be set to BANDGAP.
LESENSE has the possibility to control switches that connect the DAC outputs to the pins associated
with ACMP0_CH0-3 and ACMP1_CH12-15. This makes LESENSE able to excite sensors with output
from the DAC channels.
The DAC may be chosen as reference to the analog comparators for accurate reference generation. If
the DAC is configured in continuous or sample/hold mode this does not require any external components.
If sample/off mode is used, an external capacitor is needed to keep the voltage in between samples.
To connect the input from the DAC to the ACMP to this external capacitor, connect the capacitor to the
DAC pin for the given channel and set OPAxSHORT in DAC_OPACTRL.
Note
The DAC mode should not be altered while DACACTIVE in STATUS is set
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
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