[wpilib] Add a few unit overloads (#8231)

Co-authored-by: Sam Carlberg <sam@slfc.dev>
Co-authored-by: Joseph Eng <91924258+KangarooKoala@users.noreply.github.com>
Co-authored-by: Tyler Veness <calcmogul@gmail.com>

wpilibc/src/main/native/include/frc/Notifier.h

@@ -14,6 +14,7 @@
 #include <utility>
 
 #include <hal/Types.h>
+#include <units/frequency.h>
 #include <units/time.h>
 #include <wpi/mutex.h>
 
@@ -107,6 +108,17 @@ class Notifier {
    */
   void StartPeriodic(units::second_t period);
 
+  /**
+   * Run the callback periodically with the given frequency.
+   *
+   * The user-provided callback should be written so that it completes before
+   * the next time it's scheduled to run.
+   *
+   * @param frequency Frequency after which to call the callback starting one
+   *                  period after the call to this method.
+   */
+  void StartPeriodic(units::hertz_t frequency);
+
   /**
    * Stop further callback invocations.
    *

wpilibc/src/main/native/include/frc/TimedRobot.h

@@ -11,6 +11,7 @@
 
 #include <hal/Notifier.h>
 #include <hal/Types.h>
+#include <units/frequency.h>
 #include <units/math.h>
 #include <units/time.h>
 #include <wpi/priority_queue.h>
@@ -47,10 +48,17 @@ class TimedRobot : public IterativeRobotBase {
   /**
    * Constructor for TimedRobot.
    *
-   * @param period Period.
+   * @param period The period of the robot loop function.
    */
   explicit TimedRobot(units::second_t period = kDefaultPeriod);
 
+  /**
+   * Constructor for TimedRobot.
+   *
+   * @param frequency The frequency of the robot loop function.
+   */
+  explicit TimedRobot(units::hertz_t frequency);
+
   TimedRobot(TimedRobot&&) = default;
   TimedRobot& operator=(TimedRobot&&) = default;