Source code for wpilib.gyro

# Copyright (c) FIRST 2008-2012. All Rights Reserved.
# Open Source Software - may be modified and shared by FRC teams. The code
# must be accompanied by the FIRST BSD license file in the root directory of
# the project.

import hal

from .analoginput import AnalogInput
from .interfaces import PIDSource
from .livewindow import LiveWindow
from .sensorbase import SensorBase
from .timer import Timer

__all__ = ["Gyro"]

[docs]class Gyro(SensorBase): """Interface to a gyro device via an :class:`.AnalogInput` Use a rate gyro to return the robots heading relative to a starting position. The Gyro class tracks the robots heading based on the starting position. As the robot rotates the new heading is computed by integrating the rate of rotation returned by the sensor. When the class is instantiated, it does a short calibration routine where it samples the gyro while at rest to determine the default offset. This is subtracted from each sample to determine the heading. .. not_implemented: initGyro """ kOversampleBits = 10 kAverageBits = 0 kSamplesPerSecond = 50.0 kCalibrationSampleTime = 5.0 kDefaultVoltsPerDegreePerSecond = 0.007 def __init__(self, channel): """Gyro constructor. Also initializes the gyro. Calibrate the gyro by running for a number of samples and computing the center value. Then use the center value as the Accumulator center value for subsequent measurements. It's important to make sure that the robot is not moving while the centering calculations are in progress, this is typically done when the robot is first turned on while it's sitting at rest before the competition starts. :param channel: The analog channel index or AnalogInput object that the gyro is connected to. Gyros can only be used on on-board channels 0-1. """ if not hasattr(channel, "initAccumulator"): channel = AnalogInput(channel) self.analog = channel self.voltsPerDegreePerSecond = Gyro.kDefaultVoltsPerDegreePerSecond self.analog.setAverageBits(Gyro.kAverageBits) self.analog.setOversampleBits(Gyro.kOversampleBits) sampleRate = Gyro.kSamplesPerSecond \ * (1 << (Gyro.kAverageBits + Gyro.kOversampleBits)) AnalogInput.setGlobalSampleRate(sampleRate) Timer.delay(1.0) self.analog.initAccumulator() self.analog.resetAccumulator() # Only do this on a real robot if not hal.HALIsSimulation(): Timer.delay(Gyro.kCalibrationSampleTime) value, count = self.analog.getAccumulatorOutput() = int(float(value) / float(count) + .5) self.offset = (float(value) / float(count)) - self.analog.setAccumulatorCenter( self.analog.resetAccumulator() self.setDeadband(0.0) self.pidSource = PIDSource.PIDSourceParameter.kAngle hal.HALReport(hal.HALUsageReporting.kResourceType_Gyro, self.analog.getChannel()) LiveWindow.addSensorChannel("Gyro", self.analog.getChannel(), self)
[docs] def reset(self): """Reset the gyro. Resets the gyro to a heading of zero. This can be used if there is significant drift in the gyro and it needs to be recalibrated after it has been running. """ if self.analog is None: return self.analog.resetAccumulator()
[docs] def free(self): """Delete (free) the accumulator and the analog components used for the gyro. """ if self.analog is not None: self.analog = None
[docs] def getAngle(self): """Return the actual angle in degrees that the robot is currently facing. The angle is based on the current accumulator value corrected by the oversampling rate, the gyro type and the A/D calibration values. The angle is continuous, that is it will continue from 360 to 361 degrees. This allows algorithms that wouldn't want to see a discontinuity in the gyro output as it sweeps past from 360 to 0 on the second time around. :returns: The current heading of the robot in degrees. This heading is based on integration of the returned rate from the gyro. :rtype: float """ if self.analog is None: return 0.0 value, count = self.analog.getAccumulatorOutput() value -= count * self.offset return (value * 1e-9 * self.analog.getLSBWeight() * (1 << self.analog.getAverageBits()) / (AnalogInput.getGlobalSampleRate() * self.voltsPerDegreePerSecond))
[docs] def getRate(self): """Return the rate of rotation of the gyro The rate is based on the most recent reading of the gyro analog value :returns: the current rate in degrees per second :rtype: float """ if self.analog is None: return 0.0 else: return ((self.analog.getAverageValue() - ( + self.offset)) * 1e-9 * self.analog.getLSBWeight() / ((1 << self.analog.getOversampleBits()) * self.voltsPerDegreePerSecond))
[docs] def setSensitivity(self, voltsPerDegreePerSecond): """Set the gyro sensitivity. This takes the number of volts/degree/second sensitivity of the gyro and uses it in subsequent calculations to allow the code to work with multiple gyros. This value is typically found in the gyro datasheet. :param voltsPerDegreePerSecond: The sensitivity in Volts/degree/second :type voltsPerDegreePerSecond: float """ self.voltsPerDegreePerSecond = voltsPerDegreePerSecond
[docs] def setDeadband(self, volts): """Set the size of the neutral zone. Any voltage from the gyro less than this amount from the center is considered stationary. Setting a deadband will decrease the amount of drift when the gyro isn't rotating, but will make it less accurate. :param volts: The size of the deadband in volts :type volts: float """ if self.analog is None: return deadband = int(volts * 1e9 / self.analog.getLSBWeight() * (1 << self.analog.getOversampleBits())) self.analog.setAccumulatorDeadband(deadband)
[docs] def setPIDSourceParameter(self, pidSource): """Set which parameter of the gyro you are using as a process control variable. The Gyro class supports the rate and angle parameters. :param pidSource: An enum to select the parameter. :type pidSource: :class:`.PIDSource.PIDSourceParameter` """ if pidSource not in (PIDSource.PIDSourceParameter.kRate, PIDSource.PIDSourceParameter.kAngle): raise ValueError("Must be kRate or kAngle") self.pidSource = pidSource
[docs] def pidGet(self): """Get the output of the gyro for use with PIDControllers :returns: the current angle according to the gyro :rtype: float """ if self.pidSource == PIDSource.PIDSourceParameter.kRate: return self.getRate() elif self.pidSource == PIDSource.PIDSourceParameter.kAngle: return self.getAngle() else: return 0.0 # Live Window code, only does anything if live window is activated.
def getSmartDashboardType(self): return "Gyro" def updateTable(self): table = self.getTable() if table is not None: table.putNumber("Value", self.getAngle()) def startLiveWindowMode(self): pass def stopLiveWindowMode(self): pass