Absolute Encoders

Supported absolute encoder types for a module's absoluteEncoder field

YAGSL supports most common FRC absolute encoders. An absolute encoder is required for every module — it's what lets the angle motor know its true position on power-up, without needing to "home" against a hard stop.

The live reading shows up on the dashboard under Mechanisms/swerve/modules/<name>/encoder (degrees) — use it to find the value for absoluteEncoderOffset in each module's JSON. See Telemetry, Simulation & Vision for the full NT tree.

Absolute Encoder Checklist

• All absolute encoders read counterclockwise positive (CCW+).

• Magnetic absolute encoders get a good read on the magnet both at rest and while the robot is moving (check for wiggle/wire strain).

• Each encoder has a unique CAN ID or analog/DIO channel.

• Encoder reads the full 0°–360° range.

Configuring an absolute encoder

absoluteEncoder is a DeviceJson-shaped object, "<vendor>_<connection>":

{
  "absoluteEncoder": { "type": "cancoder_can", "id": 11, "channel": 0, "canbus": "" },
  "absoluteEncoderOffset": -18.281,
  "absoluteEncoderInverted": false
}

• absoluteEncoderOffset — degrees to add so the wheel reads 0° when facing forward with the bevel gear to the left. Read this off Raw Absolute Encoder on the dashboard with the wheel manually squared up, then enter the negative of that raw value (config.yagsl.com does this arithmetic for you).

• absoluteEncoderInverted — should rarely, if ever, need to be true.

• For encoders wired to an analog or DIO channel, set channel instead of id/canbus.

If a module spins continuously without settling, try inverting its angle motor before suspecting the absolute encoder.

Supported absolute encoder types

Device	type	Connection
REV Throughbore	revthroughbore_attached	Plugged into the angle motor controller's duty-cycle port
REV Throughbore	revthroughbore_dio	roboRIO DIO
CTRE CANcoder	cancoder_can	CAN; supports CANivore
Canandmag	canandmag_attached	Plugged into the angle motor controller's duty-cycle port
Canandmag	canandmag_dio	roboRIO DIO
Canandmag	canandmag_can	CAN
SRX Mag Encoder	srxmag_attached	Plugged into the angle motor controller's duty-cycle port
SRX Mag Encoder	srxmag_analog	roboRIO analog input
AndyMark Hex Bore	andymarkhexbore_attached	Plugged into the angle motor controller's duty-cycle port
AndyMark Hex Bore	andymarkhexbore_dio	roboRIO DIO
AndyMark Hex Bore	andymarkhexbore_analog	roboRIO analog input
AndyMark Hex Bore	andymarkhexbore_can	CAN
Spline Encoder	splineencoder_can	CAN (REV)
Generic analog (5V)	analog5v_attached	Plugged into the angle motor controller's 5V analog port
Generic analog	analog_attached	Plugged into the angle motor controller's analog port
Generic duty-cycle	dutycycle_attached	Plugged into the angle motor controller's duty-cycle port

The _attached connection means the encoder is wired directly into the angle motor controller (SparkMAX/SparkFlex duty-cycle or analog port, etc.) rather than a roboRIO or CAN device — YAGSL reads it back through that controller's vendor API. This replaces the old SwerveDrive.pushOffsetsToEncoders() mechanism from pre-2026.8.05 releases.

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General absolute encoder tips (apply regardless of device)

• Set the offset with the wheel physically squared to the robot, not by eyeballing degrees on the dashboard from an arbitrary position.

• Re-check offsets any time a module is disassembled — even a "put it back the same way" rebuild can shift the magnet by a few degrees, and swerve is unforgiving of small offset errors at low speed.

• If you swap a module between corners, its encoder wiring moves with it — the offset value does not automatically follow. See Verify Module Locations.