Absolute Encoders

YAGSL supports most common FRC absolute encoders. Absolute encoders are required if you are using a brushed motor .

The absolute encoder value will show up in shuffleboard under Module[...] Raw Absolute Encoder and can be used to tune the absoluteEncoderOffset in module JSON configuration files under most circumstances.

Absolute Encoder Checklist

• All Absolute Encoder's spin counterclockwise positive.

• Magnetic Absolute encoders have a good read on the magnet while still and in operation (while the robot moves).

• Absolute Encoders have unique CAN ID's or Analog Input Channel's.

• Absolute Encoder are defined with the correct ID or Analog Input Channel.

IF you are attaching the absolute encoder to the motor controller the gearing and counts per revolution are not relevant and should be 360 instead of the calculated conversion factor for the angle motor!

Swerve Absolute Encoder Wrapper

YAGSL created wrappers over all supported Absolute Encoders to uniformly fetch and set data that is needed for a Swerve Module to operate. This wrapper is called SwerveAbsoluteEncoder. All SwerveAbsoluteEncoder's can be fetched via the SwerveModule configuration object SwerveModuleConfiguration absolute encoder attribute absoluteEncoder. The SwerveModule is able to be fetched by SwerveDrive.getModules() easily.

YAGSL created wrappers over all supported Motor Controllers to uniformly fetch and set data that is needed for a Swerve Drive to operate. This wrapper is called SwerveMotor. All SwerveMotor's can be fetched via the SwerveModule configuration object SwerveModuleConfiguration motor definitions angleMotor and driveMotor. The SwerveModule is able to be fetched by SwerveDrive.getModules() easily.

import com.ctre.phoenix6.hardware.CANcoder;
 
   /**
   * Initialize {@link SwerveDrive} with the directory provided.
   *
   * @param directory Directory of swerve drive config files.
   */
  public SwerveSubsystem(File directory)
  {
    // Angle conversion factor is 360 / (GEAR RATIO * ENCODER RESOLUTION)
    //  In this case the gear ratio is 12.8 motor revolutions per wheel rotation.
    //  The encoder resolution per motor revolution is 1 per motor revolution.
    double angleConversionFactor = SwerveMath.calculateDegreesPerSteeringRotation(12.8, 1);
    // Motor conversion factor is (PI * WHEEL DIAMETER IN METERS) / (GEAR RATIO * ENCODER RESOLUTION).
    //  In this case the wheel diameter is 4 inches, which must be converted to meters to get meters/second.
    //  The gear ratio is 6.75 motor revolutions per wheel rotation.
    //  The encoder resolution per motor revolution is 1 per motor revolution.
    double driveConversionFactor = SwerveMath.calculateMetersPerRotation(Units.inchesToMeters(4), 6.75, 1);

    // Configure the Telemetry before creating the SwerveDrive to avoid unnecessary objects being created.
    SwerveDriveTelemetry.verbosity = TelemetryVerbosity.HIGH;
    try
    {
      swerveDrive = new SwerveParser(directory).createSwerveDrive(maximumSpeed, angleConversionFactor, driveConversionFactor);
    } catch (Exception e)
    {
      throw new RuntimeException(e);
    }
    swerveDrive.setHeadingCorrection(false); // Heading correction should only be used while controlling the robot via angle.

    for(SwerveModule m : swerveDrive.getModules())
    {
      System.out.println("Module Name: "+m.configuration.name);
      CANcoder absoluteEncoder = (CANcoder)m.configuration.absoluteEncoder.getAbsoluteEncoder();
    }
  }

Absolute Encoder Configuration

Inside any module JSON such as frontleft.json,frontright.json,backleft.json,backright.json this is what you would see to configure a absolute encoder.

{
  "drive": {
    "type": "sparkmax",
    "id": 5,
    "canbus": null
  },
  "angle": {
    "type": "sparkmax",
    "id": 6,
    "canbus": null
  },
  "encoder": {
    "type": "cancoder",
    "id": 11,
    "canbus": null
  },
  "inverted": {
    "drive": false,
    "angle": false
  },
  "absoluteEncoderOffset": -18.281,
  "location": {
    "front": -12,
    "left": -12
  }
}

Possible Absolute Encoder Types

Conversion Factor for steering/angle/azimuth motors should be 360 if the absolute encoder is attached to the SparkMAX!

Try inverting your steering/angle/azimuth motor if your module keeps spinning around.

Device	type
None	none
Integrated/Attached	attached
SparkMax Analog	sparkmax_analog
Canandcoder (via SparkMAX)	canandcoder
Canandcover (via CAN)	canandcoder_can
CANcoder	cancoder
Throughbore (via PWM)	throughbore
Thrifty Absolute Magnetic Encoder (via Analog Input)	thrifty
MA3 (via Analog Input)	ma3
SRX Mag	ctre_mag
AM Mag	am_mag
PWM DutyCycle	dutycycle
Analog Encoder	analog