> For the complete documentation index, see [llms.txt](https://yagsl.yassrobotics.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://yagsl.yassrobotics.com/reference/hardware/absolute-encoders.md). # Absolute Encoders 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//encoder` (degrees) — use it to find the value for `absoluteEncoderOffset` in each module's JSON. See [Telemetry, Simulation & Vision](/explanation/telemetry-and-vision.md) 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, `"_"`: ```json { "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`. {% hint style="warning" %} If a module spins continuously without settling, try inverting its angle motor before suspecting the absolute encoder. {% endhint %} ## Supported absolute encoder types | Device | `type` | Connection | | ----------------------------------------------------------------------------------------------------------- | -------------------------- | --------------------------------------------------------- | | [REV Throughbore](https://www.revrobotics.com/rev-11-1271/) | `revthroughbore_attached` | Plugged into the angle motor controller's duty-cycle port | | REV Throughbore | `revthroughbore_dio` | roboRIO DIO | | CTRE [CANcoder](https://pro.docs.ctr-electronics.com/en/latest/docs/hardware-reference/cancoder/index.html) | `cancoder_can` | CAN; supports CANivore | | [Canandmag](https://docs.reduxrobotics.com/canandmag/getting-started) | `canandmag_attached` | Plugged into the angle motor controller's duty-cycle port | | Canandmag | `canandmag_dio` | roboRIO DIO | | Canandmag | `canandmag_can` | CAN | | [SRX Mag Encoder](https://store.ctr-electronics.com/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](https://www.andymark.com/) | `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. *** ### 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](/how-to-guides/verify-module-locations.md). --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. 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