Create a simple wrapper/factory for "servo hats"

diozero-core/src/main/java/com/diozero/devices/ServoController.java

@@ -0,0 +1,153 @@
+package com.diozero.devices;
+
+/*
+ * #%L
+ * Organisation: diozero
+ * Project:      diozero - Core
+ * Filename:     ServoController.java
+ *
+ * This file is part of the diozero project. More information about this project
+ * can be found at https://www.diozero.com/.
+ * %%
+ * Copyright (C) 2016 - 2023 diozero
+ * %%
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ * #L%
+ */
+
+import java.util.Objects;
+
+import com.diozero.api.ServoDevice;
+import com.diozero.api.ServoTrim;
+
+/**
+ * A "wrapper" around the PCA9685 PWM controller: the main purpose is to prevent re-use of a previously allocated PWM
+ * channel.
+ * <p>
+ * <b>NOTEL</b> The servo creation allows for setting the initial angle of the servo (aka `initialPulseWidthUs`). This
+ * is <i>intended</i> to prevent the servo from "jumping" to the default position when the servo is first powered on.
+ * </p>
+ */
+public class ServoController implements AutoCloseable {
+    private final PCA9685 pwmController;
+    private final ServoDevice[] servos = new ServoDevice[16];
+
+    /**
+     * Default constructor. Uses the default PCA9685 controller.
+     */
+    public ServoController() {
+        this(new PCA9685());
+    }
+
+    /**
+     * Constructor.
+     *
+     * @param controller the PCA9685 controller to use
+     */
+    public ServoController(PCA9685 controller) {
+        pwmController = controller;
+    }
+
+    // implement singleton pattern
+    private static ServoController instance;
+
+    /**
+     * Get the singleton <b>default</b> instance of the ServoController.
+     *
+     * @return the default ServoController
+     */
+    public static synchronized ServoController getInstance() {
+        if (instance == null) {
+            instance = new ServoController();
+        }
+        return instance;
+    }
+
+    @Override
+    public void close() throws Exception {
+        pwmController.close();
+    }
+
+    /**
+     * Get a ServoDevice for the specified channel. If the channel has not been used before, a new ServoDevice will be
+     * created. If the channel has been used before, the existing ServoDevice will be returned. This will use the default
+     * trim and the initial angle <b>should</b> be 90 degrees.
+     *
+     * @param servoNumber 0-15
+     * @return the appropriate ServoDevice
+     */
+    public ServoDevice getServo(int servoNumber) {
+        return createOrGetServo(servoNumber, ServoTrim.DEFAULT, null);
+    }
+
+    /**
+     * Get a ServoDevice for the specified servo. If the servo has not been used before, a new ServoDevice will be
+     * created. If it has been used before, the existing ServoDevice will be returned. This will use the default trim.
+     *
+     * @param servoNumber 0-15
+     * @param startAngle  the initial angle
+     * @return the appropriate ServoDevice
+     */
+    public ServoDevice getServo(int servoNumber, int startAngle) {
+        return getServo(servoNumber, ServoTrim.DEFAULT, startAngle);
+    }
+
+    /**
+     * Get a ServoDevice for the specified servo. If the servo has not been used before, a new ServoDevice will be
+     * created. If it has been used before, the existing ServoDevice will be returned. The initial angle <b>should</b>
+     * be 90 degrees.
+     *
+     * @param servoNumber 0-15
+     * @param trim        Servo trim
+     * @return the appropriate ServoDevice
+     */
+    public ServoDevice getServo(int servoNumber, ServoTrim trim) {
+        return createOrGetServo(servoNumber, trim, null);
+    }
+
+    /**
+     * Get a ServoDevice for the specified servo. If the servo has not been used before, a new ServoDevice will be
+     * created. If it has been used before, the existing ServoDevice will be returned.
+     * <p>
+     * NOTE: {@code trim} and {@code startAngle} will only be applied on device creation.
+     * </p>
+     *
+     * @param servoNumber 0-15
+     * @param trim        Servo trim
+     * @param startAngle  the initial angle
+     * @return the appropriate ServoDevice
+     */
+    public ServoDevice getServo(int servoNumber, ServoTrim trim, int startAngle) {
+        return createOrGetServo(servoNumber, trim, trim.convertAngleToPulseWidthUs(startAngle));
+    }
+
+    private synchronized ServoDevice createOrGetServo(int servoNumber, ServoTrim trim, Integer initialPulseWidthUs) {
+        Objects.checkIndex(servoNumber, 16);
+
+        if (servos[servoNumber] == null) {
+            servos[servoNumber] = new ServoDevice.Builder(servoNumber)
+                    .setDeviceFactory(pwmController)
+                    .setTrim(trim)
+                    .setFrequency(pwmController.getBoardPwmFrequency())
+                    .setInitialPulseWidthUs(initialPulseWidthUs)
+                    .build();
+        }
+        return servos[servoNumber];
+    }
+}