Debouncer

A debouncer is a filter used to eliminate unwanted quick on/off cycles (termed «bounces,» originally from the physical vibrations of a switch as it is thrown). These cycles are usually due to a sensor error like noise or reflections and not the actual event the sensor is trying to record.

Debouncing is implemented in WPILib by the Debouncer class (Java, C++, Python), which filters a boolean stream so that the output only changes if the input sustains a change for some nominal time period.

Modes

The WPILib Debouncer can be configured in three different modes:

Rising (default): Debounces rising edges (transitions from false to true) only.

Falling: Debounces falling edges (transitions from true to false) only.

Both: Debounces all transitions.

Usage

JAVA

// Initializes a DigitalInput on DIO 0
DigitalInput input = new DigitalInput(0);
// Creates a Debouncer in "both" mode.
Debouncer m_debouncer = new Debouncer(0.1, Debouncer.DebounceType.kBoth);
// So if currently false the signal must go true for at least .1 seconds before being read as a True signal.
if (m_debouncer.calculate(input.get())) {
  // Do something now that the DI is True.
}

C++

// Initializes a DigitalInput on DIO 0
frc::DigitalInput input{0};
// Creates a Debouncer in "both" mode.
frc::Debouncer m_debouncer{100_ms, frc::Debouncer::DebounceType::kBoth};
// So if currently false the signal must go true for at least .1 seconds before being read as a True signal.
if (m_debouncer.calculate(input.Get())) {
  // Do something now that the DI is True.
}

PYTHON

from wpilib import DigitalInput
from wpimath.filter import Debouncer
# Initializes a DigitalInput on DIO 0
self.input = DigitalInput(0)
# Creates a Debouncer in "both" mode with a debounce time of 0.1 seconds
self.debouncer = Debouncer(0.1, Debouncer.DebounceType.kBoth)
# If currently false, the signal must go true for at least 0.1 seconds before being read as a True signal.
if self.debouncer.calculate(self.input.get()):
    # Do something now that the DI is True.
    pass