DigitalInput.java

/*
 * Copyright 2011 Ytai Ben-Tsvi. All rights reserved.
 *  
 * 
 * Redistribution and use in source and binary forms, with or without modification, are
 * permitted provided that the following conditions are met:
 * 
 *    1. Redistributions of source code must retain the above copyright notice, this list of
 *       conditions and the following disclaimer.
 * 
 *    2. Redistributions in binary form must reproduce the above copyright notice, this list
 *       of conditions and the following disclaimer in the documentation and/or other materials
 *       provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL ARSHAN POURSOHI OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * The views and conclusions contained in the software and documentation are those of the
 * authors and should not be interpreted as representing official policies, either expressed
 * or implied.
 */
package ioio.lib.api;

import ioio.lib.api.exception.ConnectionLostException;

import java.io.Closeable;

/**
 * A pin used for digital input.
 * <p>
 * A digital input pin can be used to read logic-level signals. DigitalInput
 * instances are obtained by calling {@link ioio.lib.api.IOIO#openDigitalInput(ioio.lib.api.DigitalInput.Spec)}.
 * <p>
 * The value of the pin is obtained by calling {@link #read()}. It is also
 * possible for the client to block until a certain level is sensed, by using
 * {@link #waitForValue(boolean)}.
 * <p>
 * The instance is alive since its creation. The first {@link #read()} call
 * block for a few milliseconds until the initial value is updated. If the
 * connection with the IOIO drops at any point, the instance transitions to a
 * disconnected state, in which every attempt to use the pin (except
 * {@link #close()}) will throw a {@link ioio.lib.api.exception.ConnectionLostException}. Whenever
 * {@link #close()} is invoked the instance may no longer be used. Any resources
 * associated with it are freed and can be reused.
 * <p>
 * Typical usage:
 *
 * <pre>
 * DigitalInput button = ioio.openDigitalInput(10);  // used an external pull-up
 * button.waitForValue(false);  // wait for press
 * ...
 * button.close();  // pin 10 can now be used for something else.
 * </pre>
 */
public interface DigitalInput extends Closeable
{
	/**
	 * A digital input pin specification, used when opening digital inputs.
	 */
	static public class Spec {
		/** Input pin mode. */
		public enum Mode {
			/**
			 * Pin is floating. When the pin is left disconnected the value
			 * sensed is undefined. Use this mode when an external pull-up or
			 * pull-down resistor is used or when interfacing push-pull type
			 * logic circuits.
			 */
			FLOATING,
			/**
			 * Internal pull-up resistor is used. When the pin is left
			 * disconnected, a logical "HIGH" (true) will be sensed. This is
			 * useful for interfacing with open drain circuits or for
			 * interacting with a switch connected between the pin and ground.
			 */
			PULL_UP,
			/**
			 * Internal pull-down resistor is used. When the pin is left
			 * disconnected, a logical "LOW" (false) will be sensed. This is
			 * useful for interacting with a switch connected between the pin
			 * and Vdd.
			 */
			PULL_DOWN
		}

		/** The pin number, as labeled on the board. */
		public int pin;
		/** The pin mode. */
		public Mode mode;

		/**
		 * Constructor.
		 *
		 * @param pin
		 *            Pin number, as labeled on the board.
		 * @param mode
		 *            Pin mode.
		 */
		public Spec(int pin, Mode mode) {
			this.pin = pin;
			this.mode = mode;
		}

		/** Shorthand for Spec(pin, Mode.FLOATING). */
		public Spec(int pin) {
			this(pin, Mode.FLOATING);
		}
	}

	/**
	 * Read the value sensed on the pin. May block for a few milliseconds if
	 * called right after creation of the instance. If this is a problem, the
	 * calling thread may be interrupted.
	 *
	 * @return True for logical "HIGH", false for logical "LOW".
	 * @throws InterruptedException
	 *             The calling thread has been interrupted.
	 * @throws ioio.lib.api.exception.ConnectionLostException
	 *             The connection with the IOIO has been lost.
	 */
	public boolean read() throws InterruptedException, ConnectionLostException;

	/**
	 * Block until a desired logical level is sensed. The calling thread can be
	 * interrupted for aborting this operation.
	 *
	 * @param value
	 *            The desired logical level. true for "HIGH", false for "LOW".
	 * @throws InterruptedException
	 *             The calling thread has been interrupted.
	 * @throws ioio.lib.api.exception.ConnectionLostException
	 *             The connection with the IOIO has been lost.
	 */
	public void waitForValue(boolean value) throws InterruptedException,
                                                 ConnectionLostException;
}