wpilib

junction/shims/wpilib

Replaces WPILib components to read data from junction instead of the HAL.

Replacing these classes means that user code can interact with WPILib components the same way as any other robot program. The Java export from this component is a full replacement for wpilibj that includes our shims.

Interface

The interfaces of each shim match the origin WPILib classes, replacing only the implementations. No modification is required in user code to use the shims. Below is a list of all modified classes:

• DriverStation.java - Reads joystick data from junction/core, most other functions are unmodified. This allows for synronization of data within each cycle and guarantees that data read on the robot and in the simulator are identical. Note that the method updateControlWordFromCache is unavailable as the class no longer reads a ControlWord from the HAL. This method is only used by DSControlWord by default, which remains functional.
• DSControlWord.java - Reads robot state directly from junction/core rather than DriverStation. The existing method of reading data from DriverStation required use of a ControlWord object, which the shim DriverStation is unable to create. The functionality of this class is identical.
• RobotController.java - Reads the FPGA timestamp from junction/core, all other functions are unmodified. This means that the timestamp is constant within each cycle and can be replayed accurately even when running faster than real time.
• Tracer.java - Reads the real FPGA timestamp from the HAL through junction/core instead of relying on the modified RobotController class. This class needs to read the true timestamp to accurately record epoch times.
• Watchdog.java - Reads the real FPGA timestamp from the HAL through junction/core instead of relying on the modified RobotController class. This class needs to read the true timestamp to correctly detect performance issues.

Building

The following Bazel targets are available (defined in BUILD):

• wpilib - Main Java library, depends on junction/core and WPILib for building. This library includes only the shim classes, not the rest of WPILib.
• wpilib-export - Maven export for publishing wpilib, used by GitHub Actions. This target includes runtime dependencies for both the original wpilibj and the wpilib shim target above. By explicitly depending on wpilibj (the original) first, the java_export rule replaces the duplicate class files with our shims.

To publish junction/shims/wpilib to your local Maven repository, use the following command:

bazel run --define "maven_repo=file://$HOME/.m2/repository" //junction/wpilib:wpilib-export.publish

As with all components published to Maven, the version number can be set with a command-line flag:

bazel run --define "publishing_version=X.X.X" ...

Testing

The signature-test rule checks that the method signatures of each class match the stock WPILib versions.