Update swerve drivetrain position messages & logic

This makes it so that the swerve drivetrain positions are sent in two
separate position messages (for FPGA-based and CAN-based positions),
using message definitions from the frc971/ folder.

Also refactors the SwerveModule class/usage a bit.

Removes the follower wheels from the y2024_swerve code.

Change-Id: I36898c3337b5a1437ce0c2a0189fd317929f1986
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/frc971/wpilib/swerve/swerve_module.h b/frc971/wpilib/swerve/swerve_module.h
index 729ebab..c01df24 100644
--- a/frc971/wpilib/swerve/swerve_module.h
+++ b/frc971/wpilib/swerve/swerve_module.h
@@ -1,11 +1,17 @@
 #ifndef FRC971_WPILIB_SWERVE_SWERVE_MODULE_H_
 #define FRC971_WPILIB_SWERVE_SWERVE_MODULE_H_
 
+#include "frc971/control_loops/swerve/swerve_drivetrain_can_position_static.h"
 #include "frc971/control_loops/swerve/swerve_drivetrain_output_generated.h"
+#include "frc971/control_loops/swerve/swerve_drivetrain_position_static.h"
+#include "frc971/wpilib/encoder_and_potentiometer.h"
 #include "frc971/wpilib/talonfx.h"
 
 namespace frc971::wpilib::swerve {
 
+// Contains the objects for interacting with the hardware for a given swerve
+// module, assuming that the module uses two TalonFX-based motor controllers and
+// has a CTRE mag encoder on the rotation of the module.
 struct SwerveModule {
   SwerveModule(TalonFXParams rotation_params, TalonFXParams translation_params,
                std::string canbus,
@@ -18,9 +24,10 @@
                                               signals, stator_current_limit,
                                               supply_current_limit)) {}
 
+  // Writes the requested torque currents from the module_output to the motors,
+  // setting the maximum voltage of the motor outputs to the requested value.
   void WriteModule(
-      const frc971::control_loops::drivetrain::swerve::SwerveModuleOutput
-          *module_output,
+      const frc971::control_loops::swerve::SwerveModuleOutput *module_output,
       double max_voltage) {
     double rotation_current = 0.0;
     double translation_current = 0.0;
@@ -34,8 +41,58 @@
     translation->WriteCurrent(translation_current, max_voltage);
   }
 
+  // Used during initialization to set the WPILib objects used by the mag
+  // encoder on the rotation joint.
+  void set_rotation_encoder(std::unique_ptr<frc::Encoder> encoder,
+                            std::unique_ptr<frc::DigitalInput> absolute_pwm) {
+    rotation_encoder.set_encoder(std::move(encoder));
+    rotation_encoder.set_absolute_pwm(std::move(absolute_pwm));
+  }
+
+  // Populates the Position message with the mag encoder values.
+  void PopulatePosition(
+      frc971::control_loops::swerve::SwerveModulePositionStatic *fbs) {
+    auto rotation_position = fbs->add_rotation_position();
+    rotation_position->set_encoder(rotation_encoder.ReadRelativeEncoder());
+    rotation_position->set_absolute_encoder(
+        rotation_encoder.ReadAbsoluteEncoder());
+  }
+
+  // Populates a CAN-position message with the CAN-based devices (currently,
+  // just the motors themselves).
+  void PopulateCanPosition(
+      frc971::control_loops::swerve::SwerveModuleCanPositionStatic
+          *can_position) {
+    // TODO(james): Source these numbers from the constants.json.
+    rotation->SerializePosition(can_position->add_rotation(), 1.0);
+    translation->SerializePosition(can_position->add_translation(), 1.0);
+  }
+
   std::shared_ptr<TalonFX> rotation;
   std::shared_ptr<TalonFX> translation;
+  frc971::wpilib::AbsoluteEncoder rotation_encoder;
+};
+
+// Represents all the modules in a swerve drivetrain.
+struct SwerveModules {
+  void PopulateFalconsVector(std::vector<std::shared_ptr<TalonFX>> *falcons) {
+    CHECK_NOTNULL(falcons)->push_back(front_left->rotation);
+    falcons->push_back(front_left->translation);
+
+    falcons->push_back(front_right->rotation);
+    falcons->push_back(front_right->translation);
+
+    falcons->push_back(back_left->rotation);
+    falcons->push_back(back_left->translation);
+
+    falcons->push_back(back_right->rotation);
+    falcons->push_back(back_right->translation);
+  }
+
+  std::shared_ptr<SwerveModule> front_left;
+  std::shared_ptr<SwerveModule> front_right;
+  std::shared_ptr<SwerveModule> back_left;
+  std::shared_ptr<SwerveModule> back_right;
 };
 
 }  // namespace frc971::wpilib::swerve