Package edu.wpi.first.wpilibj

Class Counter

java.lang.Object
edu.wpi.first.wpilibj.Counter
All Implemented Interfaces:
Sendable, CounterBase, AutoCloseable
public class Counter
extends Object
implements CounterBase, Sendable, AutoCloseable
Class for counting the number of ticks on a digital input channel.

This is a general purpose class for counting repetitive events. It can return the number of counts, the period of the most recent cycle, and detect when the signal being counted has stopped by supplying a maximum cycle time.

All counters will immediately start counting - reset() them if you need them to be zeroed before use.

  • Field Details

  • Constructor Details

    • Counter

      public Counter​(Counter.Mode mode)
      Create an instance of a counter with the given mode.
      Parameters:
      mode - The counter mode.

    • Counter

      public Counter()
      Create an instance of a counter where no sources are selected. Then they all must be selected by calling functions to specify the upsource and the downsource independently.

      The counter will start counting immediately.

    • Counter

      public Counter​(DigitalSource source)
      Create an instance of a counter from a Digital Input. This is used if an existing digital input is to be shared by multiple other objects such as encoders or if the Digital Source is not a DIO channel (such as an Analog Trigger)

      The counter will start counting immediately.

      Parameters:
      source - the digital source to count

    • Counter

      public Counter​(int channel)
      Create an instance of a Counter object. Create an up-Counter instance given a channel.

      The counter will start counting immediately.

      Parameters:
      channel - the DIO channel to use as the up source. 0-9 are on-board, 10-25 are on the MXP

    • Counter

      public Counter​(CounterBase.EncodingType encodingType, DigitalSource upSource, DigitalSource downSource, boolean inverted)
      Create an instance of a Counter object. Create an instance of a simple up-Counter given an analog trigger. Use the trigger state output from the analog trigger.

      The counter will start counting immediately.

      Parameters:
      encodingType - which edges to count
      upSource - first source to count
      downSource - second source for direction
      inverted - true to invert the count

    • Counter

      public Counter​(AnalogTrigger trigger)
      Create an instance of a Counter object. Create an instance of a simple up-Counter given an analog trigger. Use the trigger state output from the analog trigger.

      The counter will start counting immediately.

      Parameters:
      trigger - the analog trigger to count

  • Method Details

    • close

      public void close()
      Specified by:
      close in interface AutoCloseable

    • getFPGAIndex

      public int getFPGAIndex()
      The counter's FPGA index.
      Returns:
      the Counter's FPGA index

    • setUpSource

      public void setUpSource​(int channel)
      Set the upsource for the counter as a digital input channel.
      Parameters:
      channel - the DIO channel to count 0-9 are on-board, 10-25 are on the MXP

    • setUpSource

      public void setUpSource​(DigitalSource source)
      Set the source object that causes the counter to count up. Set the up counting DigitalSource.
      Parameters:
      source - the digital source to count

    • setUpSource

      public void setUpSource​(AnalogTrigger analogTrigger, AnalogTriggerOutput.AnalogTriggerType triggerType)
      Set the up counting source to be an analog trigger.
      Parameters:
      analogTrigger - The analog trigger object that is used for the Up Source
      triggerType - The analog trigger output that will trigger the counter.

    • setUpSourceEdge

      public void setUpSourceEdge​(boolean risingEdge, boolean fallingEdge)
      Set the edge sensitivity on an up counting source. Set the up source to either detect rising edges or falling edges.
      Parameters:
      risingEdge - true to count rising edge
      fallingEdge - true to count falling edge

    • clearUpSource

      public void clearUpSource()
      Disable the up counting source to the counter.

    • setDownSource

      public void setDownSource​(int channel)
      Set the down counting source to be a digital input channel.
      Parameters:
      channel - the DIO channel to count 0-9 are on-board, 10-25 are on the MXP

    • setDownSource

      public void setDownSource​(DigitalSource source)
      Set the source object that causes the counter to count down. Set the down counting DigitalSource.
      Parameters:
      source - the digital source to count

    • setDownSource

      public void setDownSource​(AnalogTrigger analogTrigger, AnalogTriggerOutput.AnalogTriggerType triggerType)
      Set the down counting source to be an analog trigger.
      Parameters:
      analogTrigger - The analog trigger object that is used for the Down Source
      triggerType - The analog trigger output that will trigger the counter.

    • setDownSourceEdge

      public void setDownSourceEdge​(boolean risingEdge, boolean fallingEdge)
      Set the edge sensitivity on a down counting source. Set the down source to either detect rising edges or falling edges.
      Parameters:
      risingEdge - true to count the rising edge
      fallingEdge - true to count the falling edge

    • clearDownSource

      public void clearDownSource()
      Disable the down counting source to the counter.

    • setUpDownCounterMode

      public void setUpDownCounterMode()
      Set standard up / down counting mode on this counter. Up and down counts are sourced independently from two inputs.

    • setExternalDirectionMode

      public void setExternalDirectionMode()
      Set external direction mode on this counter. Counts are sourced on the Up counter input. The Down counter input represents the direction to count.

    • setSemiPeriodMode

      public void setSemiPeriodMode​(boolean highSemiPeriod)
      Set Semi-period mode on this counter. Counts up on both rising and falling edges.
      Parameters:
      highSemiPeriod - true to count up on both rising and falling

    • setPulseLengthMode

      public void setPulseLengthMode​(double threshold)
      Configure the counter to count in up or down based on the length of the input pulse. This mode is most useful for direction sensitive gear tooth sensors.
      Parameters:
      threshold - The pulse length beyond which the counter counts the opposite direction. Units are seconds.

    • get

      public int get()
      Read the current counter value. Read the value at this instant. It may still be running, so it reflects the current value. Next time it is read, it might have a different value.
      Specified by:
      get in interface CounterBase
      Returns:
      the count

    • getDistance

      public double getDistance()
      Read the current scaled counter value. Read the value at this instant, scaled by the distance per pulse (defaults to 1).
      Returns:
      The distance since the last reset

    • reset

      public void reset()
      Reset the Counter to zero. Set the counter value to zero. This doesn't affect the running state of the counter, just sets the current value to zero.
      Specified by:
      reset in interface CounterBase

    • setMaxPeriod

      public void setMaxPeriod​(double maxPeriod)
      Set the maximum period where the device is still considered "moving". Sets the maximum period where the device is considered moving. This value is used to determine the "stopped" state of the counter using the GetStopped method.
      Specified by:
      setMaxPeriod in interface CounterBase
      Parameters:
      maxPeriod - The maximum period where the counted device is considered moving in seconds.

    • setUpdateWhenEmpty

      public void setUpdateWhenEmpty​(boolean enabled)
      Select whether you want to continue updating the event timer output when there are no samples captured. The output of the event timer has a buffer of periods that are averaged and posted to a register on the FPGA. When the timer detects that the event source has stopped (based on the MaxPeriod) the buffer of samples to be averaged is emptied. If you enable the update when empty, you will be notified of the stopped source and the event time will report 0 samples. If you disable update when empty, the most recent average will remain on the output until a new sample is acquired. You will never see 0 samples output (except when there have been no events since an FPGA reset) and you will likely not see the stopped bit become true (since it is updated at the end of an average and there are no samples to average).
      Parameters:
      enabled - true to continue updating

    • getStopped

      public boolean getStopped()
      Determine if the clock is stopped. Determine if the clocked input is stopped based on the MaxPeriod value set using the SetMaxPeriod method. If the clock exceeds the MaxPeriod, then the device (and counter) are assumed to be stopped and the method will return true.
      Specified by:
      getStopped in interface CounterBase
      Returns:
      true if the most recent counter period exceeds the MaxPeriod value set by SetMaxPeriod.

    • getDirection

      public boolean getDirection()
      The last direction the counter value changed.
      Specified by:
      getDirection in interface CounterBase
      Returns:
      The last direction the counter value changed.

    • setReverseDirection

      public void setReverseDirection​(boolean reverseDirection)
      Set the Counter to return reversed sensing on the direction. This allows counters to change the direction they are counting in the case of 1X and 2X quadrature encoding only. Any other counter mode isn't supported.
      Parameters:
      reverseDirection - true if the value counted should be negated.

    • getPeriod

      public double getPeriod()
      Get the Period of the most recent count. Returns the time interval of the most recent count. This can be used for velocity calculations to determine shaft speed.
      Specified by:
      getPeriod in interface CounterBase
      Returns:
      The period of the last two pulses in units of seconds.

    • getRate

      public double getRate()
      Get the current rate of the Counter. Read the current rate of the counter accounting for the distance per pulse value. The default value for distance per pulse (1) yields units of pulses per second.
      Returns:
      The rate in units/sec

    • setSamplesToAverage

      public void setSamplesToAverage​(int samplesToAverage)
      Set the Samples to Average which specifies the number of samples of the timer to average when calculating the period. Perform averaging to account for mechanical imperfections or as oversampling to increase resolution.
      Parameters:
      samplesToAverage - The number of samples to average from 1 to 127.

    • getSamplesToAverage

      public int getSamplesToAverage()
      Get the Samples to Average which specifies the number of samples of the timer to average when calculating the period. Perform averaging to account for mechanical imperfections or as oversampling to increase resolution.
      Returns:
      SamplesToAverage The number of samples being averaged (from 1 to 127)

    • setDistancePerPulse

      public void setDistancePerPulse​(double distancePerPulse)
      Set the distance per pulse for this counter. This sets the multiplier used to determine the distance driven based on the count value from the encoder. Set this value based on the Pulses per Revolution and factor in any gearing reductions. This distance can be in any units you like, linear or angular.
      Parameters:
      distancePerPulse - The scale factor that will be used to convert pulses to useful units.

    • initSendable

      public void initSendable​(SendableBuilder builder)
      Description copied from interface: Sendable
      Initializes this Sendable object.
      Specified by:
      initSendable in interface Sendable
      Parameters:
      builder - sendable builder