edu.wpi.first.wpilibj

Class AnalogInput

java.lang.Object

edu.wpi.first.wpilibj.SensorBase

edu.wpi.first.wpilibj.AnalogInput

All Implemented Interfaces:

LiveWindowSendable, PIDSource, Sendable

public class AnalogInput
extends SensorBase
implements PIDSource, LiveWindowSendable

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.

Field Summary

Fields

Modifier and Type	Field and Description
protected PIDSourceType	m_pidSource

Fields inherited from class edu.wpi.first.wpilibj.SensorBase

kAnalogInputChannels, kAnalogOutputChannels, kDigitalChannels, kPCMModules, kPDPChannels, kPDPModules, kPwmChannels, kRelayChannels, kSolenoidChannels, kSystemClockTicksPerMicrosecond

Constructor Summary

Constructors

Constructor and Description
AnalogInput(int channel) Construct an analog channel.

Method Summary

Modifier and Type	Method and Description
void	free() Channel destructor.
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.
PIDSourceType	getPIDSourceType() Get which parameter of the device you are using as a process control variable.
java.lang.String	getSmartDashboardType() Live Window code, only does anything if live window is activated.
ITable	getTable() The table that is associated with this Sendable.
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	initTable(ITable subtable) Initializes a table for this Sendable object.
boolean	isAccumulatorChannel() Is the channel attached to an accumulator.
double	pidGet() Get the average voltage for use with PIDController.
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	setPIDSourceType(PIDSourceType pidSource) Set which parameter of the device you are using as a process control variable.
void	startLiveWindowMode() Analog Channels don't have to do anything special when entering the LiveWindow.
void	stopLiveWindowMode() Analog Channels don't have to do anything special when exiting the LiveWindow.
void	updateTable() Update the table for this sendable object with the latest values.

Methods inherited from class edu.wpi.first.wpilibj.SensorBase

checkAnalogInputChannel, checkAnalogOutputChannel, checkDigitalChannel, checkPDPChannel, checkPDPModule, checkPWMChannel, checkRelayChannel, checkSolenoidChannel, checkSolenoidModule, getDefaultSolenoidModule, setDefaultSolenoidModule

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

m_pidSource

protected PIDSourceType m_pidSource

Constructor Detail

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 Detail

free

public void free()

Channel destructor.

Overrides:

free in class SensorBase

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.

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.

setPIDSourceType

public void setPIDSourceType(PIDSourceType pidSource)

Description copied from interface: PIDSource

Set which parameter of the device you are using as a process control variable.

Specified by:

setPIDSourceType in interface PIDSource

Parameters:

pidSource - An enum to select the parameter.

getPIDSourceType

public PIDSourceType getPIDSourceType()

Description copied from interface: PIDSource

Get which parameter of the device you are using as a process control variable.

Specified by:

getPIDSourceType in interface PIDSource

Returns:

the currently selected PID source parameter

pidGet

public double pidGet()

Get the average voltage for use with PIDController.

Specified by:

pidGet in interface PIDSource

Returns:

the average voltage

getSmartDashboardType

public java.lang.String getSmartDashboardType()

Live Window code, only does anything if live window is activated.

Specified by:

getSmartDashboardType in interface Sendable

Returns:

The type of this Sendable.

initTable

public void initTable(ITable subtable)

Description copied from interface: Sendable

Initializes a table for this Sendable object.

Specified by:

initTable in interface Sendable

Parameters:

subtable - The table to put the values in.

updateTable

public void updateTable()

Description copied from interface: LiveWindowSendable

Update the table for this sendable object with the latest values.

Specified by:

updateTable in interface LiveWindowSendable

getTable

public ITable getTable()

Description copied from interface: Sendable

The table that is associated with this Sendable.

Specified by:

getTable in interface Sendable

Returns:

the table that is currently associated with the Sendable.

startLiveWindowMode

public void startLiveWindowMode()

Analog Channels don't have to do anything special when entering the LiveWindow. Start having this sendable object automatically respond to value changes reflect the value on the table.

Specified by:

startLiveWindowMode in interface LiveWindowSendable

stopLiveWindowMode

public void stopLiveWindowMode()

Analog Channels don't have to do anything special when exiting the LiveWindow. Stop having this sendable object automatically respond to value changes.

Specified by:

stopLiveWindowMode in interface LiveWindowSendable