# 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 your driver dashboard under `swerve/modules/.../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.
* [ ] Absolute Encoders have full range (`0`-`360`)
## 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`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/encoders/SwerveAbsoluteEncoder.html). All [`SwerveAbsoluteEncoder`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/encoders/SwerveAbsoluteEncoder.html)'s can be fetched via the [`SwerveModule`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/SwerveModule.html#configuration) configuration object [`SwerveModuleConfiguration`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/parser/SwerveModuleConfiguration.html) absolute encoder attribute [`absoluteEncoder`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/parser/SwerveModuleConfiguration.html#absoluteEncoder). The [`SwerveModule`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/SwerveModule.html) is able to be fetched by [`SwerveDrive.getModules()`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/SwerveDrive.html#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`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/motors/SwerveMotor.html). All [`SwerveMotor`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/motors/SwerveMotor.html)'s can be fetched via the [`SwerveModule`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/SwerveModule.html#configuration) configuration object [`SwerveModuleConfiguration`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/parser/SwerveModuleConfiguration.html) motor definitions [`angleMotor`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/parser/SwerveModuleConfiguration.html#angleMotor) and [`driveMotor`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/parser/SwerveModuleConfiguration.html#driveMotor). The [`SwerveModule`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/SwerveModule.html) is able to be fetched by [`SwerveDrive.getModules()`](https://yet-another-software-suite.github.io/YAGSL/javadocs/swervelib/SwerveDrive.html#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
{% hint style="warning" %}
Only CTRE devices currently support the `canbus` option, if your device is using the roboRIO `canbus` you must use the value of `null` or `"rio"` for supported CTRE devices. If you are using a CANivore, and the device is on the CANivore bus, the name must match the CANivore name.
{% endhint %}
{% hint style="success" %}
If your absolute encoder is attached to your SparkMAX, use the function [`SwerveDrive.pushOffsetsToEncoders()`](https://broncbotz3481.github.io/YAGSL-Lib/docs/swervelib/SwerveDrive.html#pushOffsetsToEncoders\(\)) for the best performance. This sets the onboard PID sensor to the attached encoder!
{% endhint %}
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,
"absoluteEncoderInverted": false,
"location": {
"front": -12,
"left": -12
}
}
## Possible Absolute Encoder Types
{% hint style="warning" %}
Try inverting your steering/angle/azimuth motor if your module keeps spinning around.
{% endhint %}
[^1]: [`CANcoder`](https://api.ctr-electronics.com/phoenix6/release/java/com/ctre/phoenix6/hardware/CANcoder.html) from Phoenix 6, initialized via CAN bus and CAN ID from configurations.
[^2]: [`CANcoder`](https://api.ctr-electronics.com/phoenix6/release/java/com/ctre/phoenix6/hardware/CANcoder.html) from Phoenix 6, initialized via CAN bus and CAN ID from configurations. Cast `Object` to [`CANcoder`](https://api.ctr-electronics.com/phoenix6/release/java/com/ctre/phoenix6/hardware/CANcoder.html)
[^3]: SparkMAX brushless mode is selected.
[^4]: The SparkMAX has a CAN ID of `5`.
[^5]: SparkMAX is not compatible with CANivore so the `canbus` should be `null` or `""`.
[^6]: The SparkMAX has a CAN ID of `6`.
[^7]: [`CANcoder`](https://api.ctr-electronics.com/phoenix6/release/java/com/ctre/phoenix6/hardware/CANcoder.html) is selected using the CAN ID and bus bellow.
[^8]: [`CANcoder`](https://api.ctr-electronics.com/phoenix6/release/java/com/ctre/phoenix6/hardware/CANcoder.html) id for this module.
[^9]: CANivore name of which the [`CANcoder`](https://api.ctr-electronics.com/phoenix6/release/java/com/ctre/phoenix6/hardware/CANcoder.html) resides on.
[^10]: The drive motor spins counter clockwise positive without any inversion.
[^11]: The steering/angle/azimuth motor spins counterclockwise positive without inversion.
[^12]: Offset read from `Module[...] Raw Absolute Encoder` when the wheel was facing straight and bevels the same way.\
\
Offsets are in degrees.
[^13]: This should rarely, if ever, be true.
[^14]: The center of this module is `-12`in from the center of the robot "frontwise".
[^15]: The center of this module is `-12`in from the center of the robot "left".
[^16]: ```json
"encoder": {
"type": "attached",
"id": 11,
"canbus": null
},
```
[^17]: ```json
"encoder": {
"type": "sparkmax_analog",
"id": 11,
"canbus": null
},
```
[^18]: ```json
"encoder": {
"type": "sparkmax_analog5v",
"id": 11,
"canbus": null
},
```
[^19]: ```json
"encoder": {
"type": "canandmag",
"id": 11,
"canbus": null
},
```
[^20]: ```json
"encoder": {
"type": "canandmag_can",
"id": 11,
"canbus": null
},
```
[^21]: ```json
"encoder": {
"type": "cancoder",
"id": 11,
"canbus": null
},
```
[^22]: ```json
"encoder": {
"type": "throughbore",
"id": 11,
"canbus": null
},
```
[^23]: ```json
"encoder": {
"type": "thrifty",
"id": 11,
"canbus": null
},
```
[^24]: ```json
"encoder": {
"type": "ma3",
"id": 11,
"canbus": null
},
```
[^25]: ```json
"encoder": {
"type": "ctre_mag",
"id": 11,
"canbus": null
},
```
[^26]: ```json
"encoder": {
"type": "am_mag",
"id": 11,
"canbus": null
},
```
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