ADXL34xDevice.java

package com.buglabs.bug.module.motion.pub;

import java.io.File;
import java.io.FilenameFilter;

import com.buglabs.bug.bmi.sysfs.BMIDevice;
import com.buglabs.bug.sysfs.SysfsNode;

/**
 * Exposes sysfs entry for ADXL34x devices to Java clients.
 * 
 * @author kgilmer
 *
 */
public class ADXL34xDevice extends SysfsNode {
	
	// the accelerometer driver sysfs will be in 4-001d, 6-001d, or 7-001d depending on slot
	/* 
	 * Device entries:
	 * autosleep  
	 * calibrate  
	 * disable  
	 * driver  
	 * input  
	 * modalias	
	 * name  
	 * position	
	 * power  
	 * rate  
	 * subsystem	
	 * uevent
	 */
	private static final String ADXL_ROOT = "/sys/bus/i2c/drivers/adxl34x";
	private final int slot;
	//private final File root;

	/**
	 * @param root file root in sysfs for device entry.
	 */
	public ADXL34xDevice(File root) {
		super(root);
		slot = Integer.parseInt(root.getName().substring(0, 1)) - BMIDevice.MAX_BMI_SLOTS;	
	}
	
	/**
	 * @return The position as reported from sysfs.
	 */
	public String getPosition() {
		return getFirstLineofFile(new File(root, "position"));
	}
	
	/**
	 * @return the name of the device
	 */
	public String getName() {
		return getFirstLineofFile(new File(root, "name"));
	}
	
	/**
	 * @return the rate
	 */
	public String getRate() {
		return getFirstLineofFile(new File(root, "rate"));
	}
	
	/**
	 * @return the calibration as reported by sysfs.
	 */
	public String getCalibrate() {
		return getFirstLineofFile(new File(root, "calibrate"));
	}
	
	/**
	 * @return the slot # the device is attached to.
	 */
	public int getSlot() {
		return slot;
	}
	
	/**
	 * Get ADXL34xDevice at specified slot.
	 * @param slot 0, 2, 4 are acceptable values.
	 * @return ADXL34xDevice or null if ADXL device not attached at specified slot.
	 */
	public static ADXL34xDevice getDevice(int slot) {
		if (slot < 0 || slot == 1 || slot > 3) {
			throw new IllegalArgumentException("Slot must be 0, 2, 3");
		}
		
		ADXL34xDevice[] devices = getDevices();
		
		if (devices == null) {
			return null;
		}
		
		for (int i = 0; i < devices.length; ++i) {
			if (devices[i].getSlot() == slot) {
				return devices[i];
			}
		}
		
		return null;
	}

	/**
	 * @return An array of ADXL34 devices or null if no device exists.
	 * BUG 2.0 can contain a maximum of 3 devices.  The array index is meaningless.
	 */
	public static ADXL34xDevice[] getDevices() {
		File root = new File(ADXL_ROOT);
		
		if (!root.exists()) {
			return null;
		}
		
		File [] children = root.listFiles(new ADXLDeviceFilenameFilter());
		
		if (children == null || children.length == 0) {
			return null;
		}
		
		ADXL34xDevice[] devices = new ADXL34xDevice[children.length];
		
		for (int i = 0; i < children.length; ++i) {
			devices[i] = new ADXL34xDevice(children[i]);
		}
		
		return devices;
	}
	
	/**
	 * Based on driver convention, adxl driver directory will be [i2c address]-001d.
	 * @author kgilmer
	 *
	 */
	private static class ADXLDeviceFilenameFilter implements FilenameFilter {

		/* (non-Javadoc)
		 * @see java.io.FilenameFilter#accept(java.io.File, java.lang.String)
		 */
		public boolean accept(File dir, String name) {
			return name.endsWith("-001d");
		}
	}
}