Class AnalogInput
- java.lang.Object
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- edu.wpi.first.wpilibj.AnalogInput
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- 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.
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Constructor Summary
Constructors Constructor Description AnalogInput(int channel)
Construct an analog channel.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
close()
long
getAccumulatorCount()
Read the number of accumulated values.void
getAccumulatorOutput(AccumulatorResult result)
Read the accumulated value and the number of accumulated values atomically.long
getAccumulatorValue()
Read the accumulated value.int
getAverageBits()
Get the number of averaging bits.int
getAverageValue()
Get a sample from the output of the oversample and average engine for this channel.double
getAverageVoltage()
Get a scaled sample from the output of the oversample and average engine for this channel.int
getChannel()
Get the channel number.static double
getGlobalSampleRate()
Get the current sample rate.long
getLSBWeight()
Get the factory scaling least significant bit weight constant.int
getOffset()
Get the factory scaling offset constant.int
getOversampleBits()
Get the number of oversample bits.int
getValue()
Get a sample straight from this channel.double
getVoltage()
Get a scaled sample straight from this channel.void
initAccumulator()
Initialize the accumulator.void
initSendable(SendableBuilder builder)
Initializes thisSendable
object.boolean
isAccumulatorChannel()
Is the channel attached to an accumulator.void
resetAccumulator()
Resets the accumulator to the initial value.void
setAccumulatorCenter(int center)
Set the center value of the accumulator.void
setAccumulatorDeadband(int deadband)
Set the accumulator's deadband.void
setAccumulatorInitialValue(long initialValue)
Set an initial value for the accumulator.void
setAverageBits(int bits)
Set the number of averaging bits.static void
setGlobalSampleRate(double samplesPerSecond)
Set the sample rate per channel.void
setOversampleBits(int bits)
Set the number of oversample bits.void
setSimDevice(SimDevice device)
Indicates this input is used by a simulated device.
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Constructor Detail
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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.
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Method Detail
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close
public void close()
- Specified by:
close
in interfaceAutoCloseable
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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.
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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.
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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.
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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.
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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.
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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.
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getChannel
public int getChannel()
Get the channel number.- Returns:
- The channel number.
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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.
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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.
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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.
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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.
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initAccumulator
public void initAccumulator()
Initialize the accumulator.
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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.
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resetAccumulator
public void resetAccumulator()
Resets the accumulator to the initial value.
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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.
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setAccumulatorDeadband
public void setAccumulatorDeadband(int deadband)
Set the accumulator's deadband.- Parameters:
deadband
- The deadband size in ADC codes (12-bit value)
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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().
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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.
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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.
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isAccumulatorChannel
public boolean isAccumulatorChannel()
Is the channel attached to an accumulator.- Returns:
- The analog channel is attached to an accumulator.
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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.
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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.
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setSimDevice
public void setSimDevice(SimDevice device)
Indicates this input is used by a simulated device.- Parameters:
device
- simulated device handle
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initSendable
public void initSendable(SendableBuilder builder)
Description copied from interface:Sendable
Initializes thisSendable
object.- Specified by:
initSendable
in interfaceSendable
- Parameters:
builder
- sendable builder
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