Add HSV helpers to AddressableLED (#2135)

Also change the setLED() method to setRGB() for consistency and clarity.

Add rainbow example to demonstrate HSV usage.

wpilibcExamples/src/main/cpp/examples/AddressableLED/cpp/Robot.cpp

@@ -12,35 +12,44 @@
 #include <frc/smartdashboard/SmartDashboard.h>
 
 class Robot : public frc::TimedRobot {
+  static constexpr int kLength = 60;
+
   // PWM port 0
   // Must be a PWM header, not MXP or DIO
-  frc::AddressableLED m_led{0};
-  std::array<frc::AddressableLED::LEDData, 12> m_ledBuffer;  // Reuse the buffer
-  int m_count = 0;
+  frc::AddressableLED m_led{9};
+  std::array<frc::AddressableLED::LEDData, kLength>
+      m_ledBuffer;  // Reuse the buffer
+  // Store what the last hue of the first pixel is
+  int firstPixelHue = 0;
 
  public:
+  void Rainbow() {
+    // For every pixel
+    for (int i = 0; i < kLength; i++) {
+      // Calculate the hue - hue is easier for rainbows because the color
+      // shape is a circle so only one value needs to precess
+      const auto pixelHue = (firstPixelHue + (i * 180 / kLength)) % 180;
+      // Set the value
+      m_ledBuffer[i].SetHSV(pixelHue, 255, 128);
+    }
+    // Increase by to make the rainbow "move"
+    firstPixelHue += 3;
+    // Check bounds
+    firstPixelHue %= 180;
+  }
+
   void RobotInit() override {
-    // Default to a length of 12, start empty output
+    // Default to a length of 60, start empty output
     // Length is expensive to set, so only set it once, then just update data
-    m_led.SetLength(12);
+    m_led.SetLength(kLength);
     m_led.SetData(m_ledBuffer);
     m_led.Start();
   }
 
   void RobotPeriodic() override {
-    // Zero out all LEDs
-    for (auto& ledData : m_ledBuffer) {
-      ledData.SetLED(0, 0, 0);
-    }
-
-    // Set 1 single LED to red
-    m_ledBuffer[m_count].SetLED(50, 0, 0);
-
-    // Continue moving LED
-    m_count++;
-    if (m_count >= 12) m_count = 0;
-
-    // Buffer must be written to update.
+    // Fill the buffer with a rainbow
+    Rainbow();
+    // Set the LEDs
     m_led.SetData(m_ledBuffer);
   }
 };