i2cprotocol.java

来自「纯java操作系统jnode,安装简单和操作简单的个人使用的Java操作系统」· Java 代码 · 共 129 行

/*
 * $Id: I2cProtocol.java,v 1.1 2003/11/25 11:51:38 epr Exp $
 */
package org.jnode.driver.i2c;

/**
 * @author Ewout Prangsma ([e-mail])
 */
public class I2cProtocol implements I2cConstants {

	private final I2cAPI api;
	private final I2cLineState state = new I2cLineState();

	/**
	 * Create a new instance
	 * @param api
	 */
	public I2cProtocol(I2cAPI api) {
		this.api = api;
	}

	/**
	 * Send a single byte
	 * @param data
	 * @return The acknowledgement
	 * @throws I2cTimeoutException
	 */
	public boolean sendByte(byte data) throws I2cTimeoutException {
		for (int i = 7; i >= 0; i--) {
			if ((data & (1 << i)) != 0) {
				high();
			} else {
				low();
			}
		}
		return getAck();
	}

	/**
	 * Read a single byte
	 * @param ackRequired If true, and ack will be send after the read
	 * @return The byte read
	 * @throws I2cTimeoutException
	 */
	public int readByte(boolean ackRequired) 
	throws I2cTimeoutException {
		int i;
		int data = 0;

		/*read data*/
		api.setLines(0, 1);
		for (i = 7; i >= 0; i--) {
			api.setLines(1, 1);
			if (getData()) {
				data |= (1 << i);
			}
			api.setLines(0, 1);
		}

		/*send acknowledge*/
		if (ackRequired) {
			sendAck();
		}
		return data;
	}

	/*private final void start() {
		api.setLines(0, 1);
		api.setLines(1, 1);
		api.setLines(1, 0);
		api.setLines(0, 0);
	}*/

	/*private final void stop() {
		api.setLines(0, 0);
		api.setLines(1, 0);
		api.setLines(1, 1);
		api.setLines(0, 1);
	}*/

	private final void high() {
		api.setLines(0, 1);
		api.setLines(1, 1);
		api.setLines(0, 1);
	}

	private final void low() {
		api.setLines(0, 0);
		api.setLines(1, 0);
		api.setLines(0, 0);
	}

	private final boolean getAck() throws I2cTimeoutException {
		api.setLines(0, 1);
		api.setLines(1, 1);
		final boolean ack = getData();
		api.setLines(0, 1);
		return ack;
	}

	private final void sendAck() {
		api.setLines(0, 0);
		api.setLines(1, 0);
		api.setLines(0, 0);
	}

	private final boolean getData() throws I2cTimeoutException {
		int count = 0;
		do {
			api.getLines(state);

			/*manage timeout*/
			count++;
			if (count > I2C_TIMEOUT) {
				throw new I2cTimeoutException();
			}

			/*wait a bit, so not hammering bus*/
			try {
				Thread.sleep(I2C_DELAY);
			} catch (InterruptedException ex) {
				// Ignore
			}
		} while (!state.scl); /*wait for high clock*/
		return state.sda;
	}

}