Package edu.wpi.first.wpilibj

Class AnalogInput

java.lang.Object
edu.wpi.first.wpilibj.AnalogInput
All Implemented Interfaces:
Sendable, AutoCloseable
Direct Known Subclasses:
PIDAnalogInput
public class AnalogInput
extends Object
implements Sendable, AutoCloseable
Analog channel class.

Each analog channel is read from hardware as a 12-bit number representing 0V to 5V.

Connected to each analog channel is an averaging and oversampling engine. This engine accumulates the specified ( by setAverageBits() and setOversampleBits() ) number of samples before returning a new value. This is not a sliding window average. The only difference between the oversampled samples and the averaged samples is that the oversampled samples are simply accumulated effectively increasing the resolution, while the averaged samples are divided by the number of samples to retain the resolution, but get more stable values.

  • Constructor Details

    • AnalogInput

      public AnalogInput​(int channel)
      Construct an analog channel.
      Parameters:
      channel - The channel number to represent. 0-3 are on-board 4-7 are on the MXP port.

  • Method Details

    • close

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

    • getValue

      public int getValue()
      Get a sample straight from this channel. The sample is a 12-bit value representing the 0V to 5V range of the A/D converter. The units are in A/D converter codes. Use GetVoltage() to get the analog value in calibrated units.
      Returns:
      A sample straight from this channel.

    • getAverageValue

      public int getAverageValue()
      Get a sample from the output of the oversample and average engine for this channel. The sample is 12-bit + the bits configured in SetOversampleBits(). The value configured in setAverageBits() will cause this value to be averaged 2^bits number of samples. This is not a sliding window. The sample will not change until 2^(OversampleBits + AverageBits) samples have been acquired from this channel. Use getAverageVoltage() to get the analog value in calibrated units.
      Returns:
      A sample from the oversample and average engine for this channel.

    • getVoltage

      public double getVoltage()
      Get a scaled sample straight from this channel. The value is scaled to units of Volts using the calibrated scaling data from getLSBWeight() and getOffset().
      Returns:
      A scaled sample straight from this channel.

    • getAverageVoltage

      public double getAverageVoltage()
      Get a scaled sample from the output of the oversample and average engine for this channel. The value is scaled to units of Volts using the calibrated scaling data from getLSBWeight() and getOffset(). Using oversampling will cause this value to be higher resolution, but it will update more slowly. Using averaging will cause this value to be more stable, but it will update more slowly.
      Returns:
      A scaled sample from the output of the oversample and average engine for this channel.

    • getLSBWeight

      public long getLSBWeight()
      Get the factory scaling least significant bit weight constant. The least significant bit weight constant for the channel that was calibrated in manufacturing and stored in an eeprom.

      Volts = ((LSB_Weight * 1e-9) * raw) - (Offset * 1e-9)

      Returns:
      Least significant bit weight.

    • getOffset

      public int getOffset()
      Get the factory scaling offset constant. The offset constant for the channel that was calibrated in manufacturing and stored in an eeprom.

      Volts = ((LSB_Weight * 1e-9) * raw) - (Offset * 1e-9)

      Returns:
      Offset constant.

    • getChannel

      public int getChannel()
      Get the channel number.
      Returns:
      The channel number.

    • setAverageBits

      public void setAverageBits​(int bits)
      Set the number of averaging bits. This sets the number of averaging bits. The actual number of averaged samples is 2^bits. The averaging is done automatically in the FPGA.
      Parameters:
      bits - The number of averaging bits.

    • getAverageBits

      public int getAverageBits()
      Get the number of averaging bits. This gets the number of averaging bits from the FPGA. The actual number of averaged samples is 2^bits. The averaging is done automatically in the FPGA.
      Returns:
      The number of averaging bits.

    • setOversampleBits

      public void setOversampleBits​(int bits)
      Set the number of oversample bits. This sets the number of oversample bits. The actual number of oversampled values is 2^bits. The oversampling is done automatically in the FPGA.
      Parameters:
      bits - The number of oversample bits.

    • getOversampleBits

      public int getOversampleBits()
      Get the number of oversample bits. This gets the number of oversample bits from the FPGA. The actual number of oversampled values is 2^bits. The oversampling is done automatically in the FPGA.
      Returns:
      The number of oversample bits.

    • initAccumulator

      public void initAccumulator()
      Initialize the accumulator.

    • setAccumulatorInitialValue

      public void setAccumulatorInitialValue​(long initialValue)
      Set an initial value for the accumulator.

      This will be added to all values returned to the user.

      Parameters:
      initialValue - The value that the accumulator should start from when reset.

    • resetAccumulator

      public void resetAccumulator()
      Resets the accumulator to the initial value.

    • setAccumulatorCenter

      public void setAccumulatorCenter​(int center)
      Set the center value of the accumulator.

      The center value is subtracted from each A/D value before it is added to the accumulator. This is used for the center value of devices like gyros and accelerometers to take the device offset into account when integrating.

      This center value is based on the output of the oversampled and averaged source the accumulator channel. Because of this, any non-zero oversample bits will affect the size of the value for this field.

      Parameters:
      center - The accumulator's center value.

    • setAccumulatorDeadband

      public void setAccumulatorDeadband​(int deadband)
      Set the accumulator's deadband.
      Parameters:
      deadband - The deadband size in ADC codes (12-bit value)

    • getAccumulatorValue

      public long getAccumulatorValue()
      Read the accumulated value.

      Read the value that has been accumulating. The accumulator is attached after the oversample and average engine.

      Returns:
      The 64-bit value accumulated since the last Reset().

    • getAccumulatorCount

      public long getAccumulatorCount()
      Read the number of accumulated values.

      Read the count of the accumulated values since the accumulator was last Reset().

      Returns:
      The number of times samples from the channel were accumulated.

    • getAccumulatorOutput

      public void getAccumulatorOutput​(AccumulatorResult result)
      Read the accumulated value and the number of accumulated values atomically.

      This function reads the value and count from the FPGA atomically. This can be used for averaging.

      Parameters:
      result - AccumulatorResult object to store the results in.

    • isAccumulatorChannel

      public boolean isAccumulatorChannel()
      Is the channel attached to an accumulator.
      Returns:
      The analog channel is attached to an accumulator.

    • setGlobalSampleRate

      public static void setGlobalSampleRate​(double samplesPerSecond)
      Set the sample rate per channel.

      This is a global setting for all channels. The maximum rate is 500kS/s divided by the number of channels in use. This is 62500 samples/s per channel if all 8 channels are used.

      Parameters:
      samplesPerSecond - The number of samples per second.

    • getGlobalSampleRate

      public static double getGlobalSampleRate()
      Get the current sample rate.

      This assumes one entry in the scan list. This is a global setting for all channels.

      Returns:
      Sample rate.

    • setSimDevice

      public void setSimDevice​(SimDevice device)
      Indicates this input is used by a simulated device.
      Parameters:
      device - simulated device handle

    • 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