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75 lines
3.2 KiB
Python
75 lines
3.2 KiB
Python
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#!/usr/bin/env python3
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#
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# Copyright (c) FIRST and other WPILib contributors.
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# Open Source Software; you can modify and/or share it under the terms of
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# the WPILib BSD license file in the root directory of this project.
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#
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"""
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This example shows how to use a duty cycle encoder for devices such as
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an arm or elevator.
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"""
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import wpilib
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import wpimath
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FULL_RANGE = 1.3
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EXPECTED_ZERO = 0.0
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class MyRobot(wpilib.TimedRobot):
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def __init__(self):
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"""Called once at the beginning of the robot program."""
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super().__init__()
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# 2nd parameter is the range of values. This sensor will output between
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# 0 and the passed in value.
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# 3rd parameter is the the physical value where you want "0" to be. How
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# to measure this is fairly easy. Set the value to 0, place the mechanism
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# where you want "0" to be, and observe the value on the dashboard, That
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# is the value to enter for the 3rd parameter.
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self.dutyCycleEncoder = wpilib.DutyCycleEncoder(0, FULL_RANGE, EXPECTED_ZERO)
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# If you know the frequency of your sensor, uncomment the following
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# method, and set the method to the frequency of your sensor.
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# This will result in more stable readings from the sensor.
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# Do note that occasionally the datasheet cannot be trusted
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# and you should measure this value. You can do so with either
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# an oscilloscope, or by observing the "Frequency" output
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# on the dashboard while running this sample. If you find
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# the value jumping between the 2 values, enter halfway between
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# those values. This number doesn't have to be perfect,
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# just having a fairly close value will make the output readings
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# much more stable.
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self.dutyCycleEncoder.setAssumedFrequency(967.8)
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def robotPeriodic(self):
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# Connected can be checked, and uses the frequency of the encoder
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connected = self.dutyCycleEncoder.isConnected()
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# Duty Cycle Frequency in Hz
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frequency = self.dutyCycleEncoder.getFrequency()
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# Output of encoder
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output = self.dutyCycleEncoder.get()
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# By default, the output will wrap around to the full range value
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# when the sensor goes below 0. However, for moving mechanisms this
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# is not usually ideal, as if 0 is set to a hard stop, its still
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# possible for the sensor to move slightly past. If this happens
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# The sensor will assume its now at the furthest away position,
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# which control algorithms might not handle correctly. Therefore
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# it can be a good idea to slightly shift the output so the sensor
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# can go a bit negative before wrapping. Usually 10% or so is fine.
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# This does not change where "0" is, so no calibration numbers need
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# to be changed.
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percentOfRange = FULL_RANGE * 0.1
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shiftedOutput = wpimath.inputModulus(
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output, 0 - percentOfRange, FULL_RANGE - percentOfRange
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)
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wpilib.SmartDashboard.putBoolean("Connected", connected)
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wpilib.SmartDashboard.putNumber("Frequency", frequency)
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wpilib.SmartDashboard.putNumber("Output", output)
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wpilib.SmartDashboard.putNumber("ShiftedOutput", shiftedOutput)
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