> 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/how-to-guides/determine-inversion.md).

# Determine inversion

Swerve modules and swerve drives require some inversions to get working properly. The goal is to get everything to increase **counter-clockwise positive (CCW+)**.

{% hint style="info" %}
[config.yagsl.com/guide](https://config.yagsl.com/guide) walks through this exact process interactively, with animations, if you'd rather follow along there instead of on this page.
{% endhint %}

{% hint style="warning" %}
If your gears are grinding on the ground but not while on blocks, and your wheels are facing and spinning in the right directions, you may need to [tune PID](/how-to-guides/tune-pidf-gains.md) instead of inverting anything!
{% endhint %}

{% hint style="warning" %}
If you invert incorrectly, your modules or robot may spin "out of control." If nothing here resolves it, see [The 8 steps](/how-to-guides/the-8-steps.md).
{% endhint %}

All of the telemetry referenced below lives under `Mechanisms/swerve` in NetworkTables — see [Telemetry, Simulation & Vision](/explanation/telemetry-and-vision.md) for the full tree.

## 1. Confirm the absolute encoder reads CCW+

<figure><img src="/files/mI3Vo1gWfvt34By0CQQR" alt=""><figcaption><p>Purple shows the way your bevels should be facing (photo by Team 2876)</p></figcaption></figure>

With the robot lifted or on its side so the wheels spin freely, rotate one module by hand **counterclockwise** (viewed from directly above, robot front pointing away from you) and watch that module's `modules/<name>/encoder` value in AdvantageScope.

* If it **increases**, the absolute encoder is already correct — leave `absoluteEncoderInverted` as `false`.
* If it **decreases**, set `absoluteEncoderInverted` to `true` for that module. This is rare — most absolute encoders already read CCW+ by default.

```json
{
  "drive": { "type": "sparkmax_neo", "id": 2, "canbus": "" },
  "angle": { "type": "sparkmax_neo", "id": 1, "canbus": "" },
  "absoluteEncoder": { "type": "cancoder_can", "id": 10, "channel": 0, "canbus": "" },
  "inverted": { "drive": false, "angle": false },
  "absoluteEncoderInverted": true,
  "absoluteEncoderOffset": -50.977,
  "location": { "front": 12, "left": -12 }
}
```

Once every module reads CCW+, rotate each wheel to point straight forward (bevel gear left) and record the `modules/<name>/encoder` value held in that position — that's the module's `absoluteEncoderOffset`. Enter it in the module's JSON, or paste it into [**config.yagsl.com**](https://config.yagsl.com).

## 2. Confirm the gyro reads CCW+

With the robot lifted off the ground, rotate the **entire robot** counterclockwise (viewed from above) and watch `Mechanisms/swerve/gyro`.

* If it **increases**, leave `gyroInvert` alone — there's nothing to change.
* If it **decreases**, set `gyroInvert` to `true` in `swervedrive.json`:

```json
{
  "gyro": { "type": "pigeon2_can", "id": 13, "canbus": "canivore" },
  "gyroAxis": "yaw",
  "gyroInvert": true,
  "modules": ["frontleft.json", "frontright.json", "backleft.json", "backright.json"]
}
```

See the [gyroscope reference](/reference/hardware/gyroscopes.md) for the full list of supported `gyro.type` values.

## 3. Spin test — catch drive motor inversion and module swaps

Still with the robot lifted off the ground, deploy code and drive with a joystick input that commands pure rotation (e.g. hold the rotation stick fully to one side). Watch the robot against AdvantageScope's Swerve widget (top-down view) — see [Set up AdvantageScope](/how-to-guides/set-up-advantagescope.md) — and compare:

| Symptom                                                         | Likely cause                                                                                                                                                                                 |
| --------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Modules drift or translate instead of spinning cleanly in place | Wrong CAN IDs for a module, or a wrong `absoluteEncoderOffset`.                                                                                                                              |
| Spins cleanly, but the wrong way (clockwise instead of CCW)     | Inverted drive motor(s); a diagonal module swap (front-left ↔ back-right, front-right ↔ back-left); or an absolute encoder offset captured with the bevel gear facing right instead of left. |

If a single module is spinning the wrong way, invert that module's drive motor:

```json
{
  "drive": { "type": "sparkmax_neo", "id": 2, "canbus": "" },
  "angle": { "type": "sparkmax_neo", "id": 1, "canbus": "" },
  "absoluteEncoder": { "type": "cancoder_can", "id": 10, "channel": 0, "canbus": "" },
  "inverted": { "drive": true, "angle": false },
  "absoluteEncoderInverted": false,
  "absoluteEncoderOffset": -50.977,
  "location": { "front": 12, "left": -12 }
}
```

If every module spins the wrong way at once, double-check for a diagonal module swap in `swervedrive.json`'s `modules` list before you start flipping individual `inverted.drive` fields — it's a more common cause than it sounds.

## 4. Field-orientation check

Once the spin test looks right, put the robot down and drive it forward/back/left/right at its starting heading while watching a 2D/3D Field tab fed from `Mechanisms/swerve/pose`. Then spin in place again, this time watching the field widget's heading instead of the swerve module widget.

* **Wrong at every heading, including the start:** check `gyroInvert`.
* **Only wrong once you rotate away from the starting heading:** an absolute encoder offset that's off, a drive motor inversion mistake, a wrong module `location`, an absolute encoder wired to the wrong motor controller, or a wrong CAN ID. Verify wiring and CAN IDs first — they're the fastest to rule out.
* **The spin test in step 3 looked right, but the field widget's heading spins backwards:** an inverted gyro can flip the field widget even when the module states widget looked correct.

{% hint style="danger" %}

#### Odometry mismatch

If your robot drives backwards in odometry but forwards in real life, while a spin-in-place still shows Counter-Clockwise-Positive movement, apply this patch: add `180` to every `absoluteEncoderOffset` in every module file.
{% endhint %}

{% hint style="info" %}
In older YAGSL configs (pre-2026.8.05) this section was named `imu`/`invertedIMU` instead of `gyro`/`gyroInvert` — see the [schema changes reference](/reference/schema-changes.md) if you're working from an old config.
{% endhint %}


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