4. seven steps to an Raspberry Pi application

1) Prepare your Raspberry Pi:

• install Raspbian (Debian Wheezy) ([get it here](http://www.raspberrypi.org/downloads/))
• install a Java 1.7 using

`>apt-get install oracle-java7-jdk `

2) change directory to /usr/local

`root@raspberrypi:/#cd /usr/local`

3) Download the tarball RaspberryPiSample.tar.

4) extract the tarball

`root@raspberrypi:/usr/local# tar -xzf ./RaspberryPiSample.tar`

A directory named /usr/local/application should show up now with the following contence:


5) change directory to /usr/local/application

`root@raspberrypi:/usr/local#cd ./application`

6) shortcircuit pin’s 4 and 5 of your Raspberry Pi.


7) start the the shell script

`root@raspberrypi:/usr/local/application# ./applicationloop.sh`

and look what you get on your console:

16:51:03,898 [INFO:JPac] STARTING
16:51:03,921 [INFO:JPac] awaiting start up signal ...
16:51:04,899 [INFO:main] startCycling requested
16:51:04,908 [INFO:main] startCycling() acknowledged
16:51:04,930 [INFO:JPac] starting up org.jpac.vioss.raspi.gpio.IOHandler(raspigpio:)
16:51:04,984 [INFO:JPac] running in LazyBound mode ...
16:51:05,019 [INFO:MainModule.ReadbackPinModule] started ...
16:51:05,042 [INFO:MainModule.TogglePinModule] started ...
16:51:05,092 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = false)
16:51:06,095 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = true)
16:51:07,100 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = false)
16:51:08,103 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = true)
16:51:09,108 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = false)
16:51:10,113 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = true)
16:51:11,118 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = false)
16:51:12,122 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = true)
16:51:13,127 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = false)
16:51:14,031 [INFO:MainModule.TogglePinModule] delaying toggle ...
16:51:14,133 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = true)
16:51:16,143 [INFO:MainModule.ReadbackPinModule] !!!!!!!!!!!!!! toggle time exceeded !!!!!!!!!!!!!!!!!!!!!
16:51:16,146 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = true)
16:51:17,146 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = false)
16:51:18,149 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = true)
16:51:19,152 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = false)
16:51:20,157 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = true)
16:51:21,161 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = false)
16:51:22,165 [INFO:MainModule.ReadbackPinModule] pin #5: LogicalInput(MainModule.ReadbackPinModule.RaspiInputPin05 = true)

If you get something like shown above: Congratulation, your raspberry application works.

You can stop it by pressing CTRL-C:

^C16:51:22,949 [INFO:ShutdownHook] shutdown requested. Informing jPac ...
16:51:22,967 [INFO:JPac] storing histogramm informationen to ./data/histogramm.csv
16:51:22,989 [INFO:JPac] shutting down modules ...
16:51:22,996 [ERROR:MainModule.ReadbackPinModule] shutting down ... 
16:51:23,002 [INFO:JPac] ... shutting down modules done
16:51:23,005 [INFO:JPac] shutting down ...org.jpac.vioss.raspi.gpio.IOHandler(raspigpio:)
16:51:23,010 [INFO:JPac] cycle mode               : LazyBound
16:51:23,014 [INFO:JPac] cycle time               : 100000000 ns
16:51:23,017 [INFO:JPac] min remaining cycle time : 89637242 ns (89%)
16:51:23,019 [INFO:JPac] max remaining cycle time : 99249017 ns (99%)
16:51:23,022 [INFO:JPac] SHUTDOWN COMPLETE
16:51:23,110 [INFO:ShutdownHook] shutdown complete

1. Let’s take a closer look at our s(a)imple elbfisch application.

It consists of 4 Java classes:


• Sample is the formal main program which is used to instantiate the elbfisch modules
• MainModule is the main module of this elbfisch application. It instantiates the following modules.
• TogglePinModule simply toggles gpio pin#4 of our raspberry pi once a second
• ReadbackPinModule simply waits for gpio pin#5 to toggle and generates an apropriate log message

/**
 * PROJECT   : Elbfisch - java process automation controller (jPac)
 * MODULE    : TogglePinModule.java
 * VERSION   : -
 * DATE      : -
 * PURPOSE   : 
 * AUTHOR    : Bernd Schuster, MSK Gesellschaft fuer Automatisierung mbH, Schenefeld
 * REMARKS   : -
 * CHANGES   : CH#n <Kuerzel> <datum> <Beschreibung>
 *
 * This file is part of the jPac process automation controller.
 * jPac is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * jPac is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with the jPac If not, see <http://www.gnu.org/licenses/>.
 */

package raspberry;

import java.net.URI;
import java.net.URISyntaxException;
import org.jpac.AbstractModule;
import org.jpac.InconsistencyException;
import org.jpac.InputInterlockException;
import org.jpac.Module;
import org.jpac.OutputInterlockException;
import org.jpac.PeriodOfTime;
import org.jpac.ProcessException;
import org.jpac.SignalAlreadyExistsException;
import org.jpac.WrongUseException;
import org.jpac.vioss.raspi.gpio.LogicalOutput;

/**
 *
 * @author berndschuster
 */
public class TogglePinModule extends Module{
    
    private LogicalOutput pin4;
    
    public TogglePinModule(AbstractModule containingModule, String identifier) throws SignalAlreadyExistsException, InconsistencyException, WrongUseException, URISyntaxException{
        super(containingModule, identifier);
        pin4 = new LogicalOutput(this, "RaspiOutputPin04", new URI("raspigpio:/4"));
    }
    
    @Override
    protected void work() throws ProcessException {
        PeriodOfTime toggleTime         = new PeriodOfTime(1 * sec);//instantiate a period of time event (1 s)
        PeriodOfTime extendedToggleTime = new PeriodOfTime(3 * sec);//instantiate a period of time event (1 s)
        int          cycleCounter       = 0;
        Log.info("started ...");
        pin4.set(false);
        do{
            if (++cycleCounter % 10 != 0){
                toggleTime.await();//wait for 1 second
            }
            else{
                Log.info("delaying toggle ...");
                extendedToggleTime.await();
            }
            pin4.set(!pin4.is(true));
            //Log.info("toggled " + pin4);
        }
        while(true);    
    }

    @Override
    protected void preCheckInterlocks() throws InputInterlockException {
    }

    @Override
    protected void postCheckInterlocks() throws OutputInterlockException {
    }

    @Override
    protected void inEveryCycleDo() throws ProcessException {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}