Datasheet

 2010-2011 Microchip Technology Inc. DS41418B-page 119
PIC16(L)F707
16.0 CAPACITIVE SENSING
MODULE
The capacitive sensing modules (CSM) allow for an
interaction with an end user without a mechanical
interface. In a typical application, the capacitive
sensing module is attached to a pad on a Printed
Circuit Board (PCB), which is electrically isolated from
the end user. When the end user places their finger
over the PCB pad, a capacitive load is added, causing
a frequency shift in the capacitive sensing module. The
capacitive sensing module requires software and at
least one timer resource to determine the change in
frequency. Key features of this module include:
• Analog MUX for monitoring multiple inputs
• Capacitive sensing oscillator
• Multiple Power modes
• High power range with variable voltage
references
• Multiple timer resources
• Software control
• Operation during sleep
• Acquire two samples simultaneously (when using
both CSM modules)
Two identical capacitive sensing modules are
implemented on the PIC16F707/PIC16LF707. The
modules are named CPSA and CPSB. The timer
module integration for both capacitive sensing modules
is shown in Table 16-1. A block diagram of the
capacitive sensing module is shown in Figure 16-1 and
Figure 16-2.
TABLE 16-1: CPSOSC TIMER USAGE
Cap Sense Oscillator Mode Frequency Measurement Duration Control
Cap Sense Oscillator A
TimerA/Software TimerA Software
Timer1/Software Timer1 Software
Timer1/TimerA Timer1 TimerA
Cap Sense Oscillator B
TimerB/Software TimerB Software
Timer3/Software Timer3 Software
Timer3/TimerB Timer3 TimerB