GpioStepperMotorComponent.java

package com.pi4j.component.motor.impl;

/*
 * #%L
 * **********************************************************************
 * ORGANIZATION  :  Pi4J
 * PROJECT       :  Pi4J :: Device Abstractions
 * FILENAME      :  GpioStepperMotorComponent.java  
 * 
 * This file is part of the Pi4J project. More information about 
 * this project can be found here:  http://www.pi4j.com/
 * **********************************************************************
 * %%
 * Copyright (C) 2012 - 2013 Pi4J
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */

import com.pi4j.component.motor.MotorState;
import com.pi4j.component.motor.StepperMotorBase;
import com.pi4j.io.gpio.GpioPinDigitalOutput;
import com.pi4j.io.gpio.PinState;

public class GpioStepperMotorComponent extends StepperMotorBase {
    
    // internal class members
    private GpioPinDigitalOutput pins[];
    private PinState onState = PinState.HIGH;
    private PinState offState = PinState.LOW;
    private MotorState currentState = MotorState.STOP;
    private GpioStepperMotorControl controlThread = new GpioStepperMotorControl();
    private int sequenceIndex = 0;

    /**
     * using this constructor requires that the consumer 
     *  define the STEP ON and STEP OFF pin states 
     *  
     * @param pins GPIO digital output pins for each controller in the stepper motor 
     * @param onState pin state to set when MOTOR STEP is ON
     * @param offState pin state to set when MOTOR STEP is OFF
     */
    public GpioStepperMotorComponent(GpioPinDigitalOutput pins[], PinState onState, PinState offState) {
        this.pins = pins;
        this.onState = onState;
        this.offState = offState;
    }

    /**
     * default constructor; using this constructor assumes that:
     *  (1) a pin state of HIGH is MOTOR STEP ON
     *  (2) a pin state of LOW  is MOTOR STEP OFF
     *  
     * @param pins GPIO digital output pins for each controller in the stepper motor 
     */
    public GpioStepperMotorComponent(GpioPinDigitalOutput pins[]) {
        this.pins = pins;
    }

    /**
     * Return the current motor state  
     *  
     * @return MotorState 
     */
    @Override
    public MotorState getState() {
        return currentState;
    }

    /**
     * change the current stepper motor state 
     * 
     * @param state new motor state to apply
     */
    @Override
    public void setState(MotorState state) {
        
        switch(state) {
            case STOP: {
                // set internal tracking state
                currentState = MotorState.STOP;
                
                // turn all GPIO pins to OFF state
                for(GpioPinDigitalOutput pin : pins)
                    pin.setState(offState);
                
                break;
            }
            case FORWARD: {
                // set internal tracking state
                currentState = MotorState.FORWARD;
                
                // start control thread if not already running
                if(!controlThread.isAlive()) {
                    controlThread = new GpioStepperMotorControl();                    
                    controlThread.start();
                }
                
                break;
            }
            case REVERSE: {
                // set internal tracking state
                currentState = MotorState.REVERSE;
                
                // start control thread if not already running
                if(!controlThread.isAlive()) {
                    controlThread = new GpioStepperMotorControl();
                    controlThread.start();
                }
                
                break;
            }
            default: {
                throw new UnsupportedOperationException("Cannot set motor state: " + state.toString());
            }
        }
    }
    
    private class GpioStepperMotorControl extends Thread {
        public void run() {

            // continuous loop until stopped
            while(currentState != MotorState.STOP) {
                
                // control direction 
                if(currentState == MotorState.FORWARD)
                    doStep(true);
                else if(currentState == MotorState.REVERSE)
                    doStep(false);
            }
            
            // turn all GPIO pins to OFF state
            for(GpioPinDigitalOutput pin : pins)
                pin.setState(offState);            
        }        
    }
    
    @Override
    public void step(long steps)
    {        
        // validate parameters
        if (steps == 0) {        
            setState(MotorState.STOP);
            return;
        }

        // perform step in positive or negative direction from current position
        if (steps > 0){
            for(long index = 1; index <= steps; index++)
                doStep(true);
        }
        else {
            for(long index = steps; index < 0; index++)
                doStep(false);
        }
        
        // stop motor movement
        this.stop();
    }
    
    /**
     * this method performs the calculations and work to control the GPIO pins
     * to move the stepper motor forward or reverse 
     * @param forward
     */
    private void doStep(boolean forward) {

        // increment or decrement sequence
        if(forward)
            sequenceIndex++;
        else
            sequenceIndex--;
        
        // check sequence bounds; rollover if needed
        if(sequenceIndex >= stepSequence.length)
            sequenceIndex = 0;
        else if(sequenceIndex < 0)
            sequenceIndex = (stepSequence.length - 1);

        // start cycling GPIO pins to move the motor forward or reverse
        for(int pinIndex = 0; pinIndex < pins.length; pinIndex++) {
            // apply step sequence 
            double nib = Math.pow(2, pinIndex);
            if((stepSequence[sequenceIndex] & (int)nib) > 0)
                pins[pinIndex].setState(onState);
            else
                pins[pinIndex].setState(offState);
        }            
        try {
            Thread.sleep(stepIntervalMilliseconds, stepIntervalNanoseconds);
        }
        catch (InterruptedException e) {}        
    }    
}