User manual

...the world's most energy friendly microcontrollers
2012-04-24 - Giant Gecko Family - d0053_Rev0.96 620
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25.3.4 Sensor interaction
Many sensor types require some type of excitation in order to work. LESENSE can generate a variety
of sensor stimuli, both on the same pin as the measurement is to be made on, and on alternative pins.
By default, excitation is performed on the pin associated with the channel, i.e. excitation and sensor
measurement is performed on the same pin. The mode of the pin during the excitation phase is
configured in EXMODE in CHx_INTERACT. The available modes during the excite phase are:
• DISABLED: The pin is disabled.
• HIGH: The pin is driven high.
• LOW: The pin is driven low.
• DACOUT: The pin is connected to the output of a DAC channel.
Note
Excitation with DAC output is only available on channels 0, 1, 2, and 3 (DAC0_CH0) and
channels 12, 13, 14, and 15 (DAC0_CH1).
If the DAC is in opamp-mode, setting EXMODE to DACOUT will result in excitation with
output from the opamp.
LESENSE is able to perform sensor excitation on another pin than the one to be measured. When
ALTEX in CHx_INTERACT is set, the excitation will occur on the alternative excite pin associated with
the given channel. All LESENSE channels mapped to ACMP0 have their alternative channel mapped
to the corresponding channel on ACMP1, and vice versa. Alternatively, the alternative excite pins can
be routed to the LES_ALTEX pins. Mapping of the alternative excite pins is configured in ALTEXMAP
in CTRL. Table 25.2 (p. 620) summarizes the mapping of excitation pins for different configurations.
Table 25.2. LESENSE excitation pin mapping
ALTEX = 0 ALTEX = 1
LESENSE channel
ALTEXMAP = ACMP ALTEXMAP = ALTEX
0 ACMP0_CH0 ACMP1_CH0 LES_ALTEX0
1 ACMP0_CH1 ACMP1_CH1 LES_ALTEX1
2 ACMP0_CH2 ACMP1_CH2 LES_ALTEX2
3 ACMP0_CH3 ACMP1_CH3 LES_ALTEX3
4 ACMP0_CH4 ACMP1_CH4 LES_ALTEX4
5 ACMP0_CH5 ACMP1_CH5 LES_ALTEX5
6 ACMP0_CH6 ACMP1_CH6 LES_ALTEX6
7 ACMP0_CH7 ACMP1_CH7 LES_ALTEX7
8 ACMP1_CH0 ACMP0_CH0 LES_ALTEX0
9 ACMP1_CH1 ACMP0_CH1 LES_ALTEX1
10 ACMP1_CH2 ACMP0_CH2 LES_ALTEX2
11 ACMP1_CH3 ACMP0_CH3 LES_ALTEX3
12 ACMP1_CH4 ACMP0_CH4 LES_ALTEX4
13 ACMP1_CH5 ACMP0_CH5 LES_ALTEX5
14 ACMP1_CH6 ACMP0_CH6 LES_ALTEX6
15 ACMP1_CH7 ACMP0_CH7 LES_ALTEX7