User manual

...the world's most energy friendly microcontrollers
2013-10-10 - t0014_0.21 8
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5.3 Capacitive Touch Slider
A touch slider utilizing the capacitive touch capability is available. It is placed beneath the two push
buttons on the kit. The slider interpolates 4 separate pads to find the exact position of a finger. For low
power operation, the touch slider can be used together with LESENSE to continuously scan all 4 pads,
using LESENSE channels 8 to 11.
Figure 5.3. Touch Slider
Touch Slider
PC10 (ACMP1_CH2)
PC11 (ACMP1_CH3)
PC8 (ACMP1_CH0)
PC9 (ACMP1_CH1)
UIF_TOUCH0
UIF_TOUCH1
UIF_TOUCH2
UIF_TOUCH3
EFM32 MCU
The capacitive touch slider works by sensing changes in the capacitance of the pads when touched by a
human finger. Sensing the changes in capacitance is done by setting up the touch pad as part of an RC
relaxation oscillator using the EFM32's analog comparator, and then counting the number of oscillations
during a fixed period of time.
5.4 Ambient Light Sensor
The kit has a light sensitive, transistor type, ambient light sensor connected to the low energy sensor
interface of the EFM32 Giant Gecko MCU. The sensor is placed above the push buttons and can be
used to sense changes in ambient light levels.
Figure 5.4. Light Sensor
LIGHT_EXCITE
LIGHT_SENSE
22K
TEMT6200FX01
PD6 (LES_ALTEX0)
PC6 (ACMP0_CH6)
EFM32 MCU
Two pins are used for the light sensor operation: one for excitation, and one for sensing. The sense pin
is connected to ACMP0 CH6. Both the excitation pin and the sense pin can be controlled directly from
the EFM32's LESENSE module.