C8051F980-C-GM Datasheet, PDF (100/325 Pages) Silicon Laboratories – Ultra Low Power, 8-2 kB Flash, Capacitive Sensing MCU

C8051F99x-C8051F98x
8. Capacitive Sense (CS0)
The Capacitive Sense subsystem uses a capacitance-to-digital circuit to determine the capacitance on a
port pin. The module can take measurements from different port pins using the module’s analog
multiplexer. The module is enabled only when the CS0EN bit (CS0CN) is set to 1. Otherwise the module is
in a low-power shutdown state. The module can be configured to take measurements on one port pin or a
group of port pins, using auto-scan. A selectable gain circuit allows the designer to adjust the maximum
allowable capacitance. An accumulator is also included, which can be configured to average multiple
conversions on an input channel. Interrupts can be generated when CS0 completes a conversion or when
the measured value crosses a threshold defined in CS0THH:L.
CS0PM
CS0CN
CS0CF
CS0SS CS0SE
Auto-Scan
Logic
CS0MX
Pin Monitor
Port I/O and
Peripherals
000
Start
001
Conversion
010
011
100
101
110
111
CS0BUSY (W)
Timer 0 Overflow
Timer 2 Overflow
Timer 1 Overflow
Timer 3 Overflow
Reserved
Initiated continuously
Initiated continuously
when auto-scan
enabled
1x-8x
Capacitance to ^{12, 13, 14, or 16 bits}
22-Bit Accumulator
Digital Converter
...
CS0DH:L
Greater Than
Compare Logic
CS0CMPF
CS0MD1
CS0MD2
CS0MD3
CS0THH:L
Figure 8.1. CS0 Block Diagram
100
Rev. 1.2