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
root@raspberrypi:/apt-get install oracle-java7-jdk2) change directory to /usr/local
root@raspberrypi:/#cd /usr/local3) Download the tarball RaspberryPiSample.tar.
4) extract the tarball
root@raspberrypi:/usr/local# tar -xzf ./RaspberryPiSample.tar
5) change directory to /usr/local/application
root@raspberrypi:/usr/local#cd ./application6) shortcircuit pin’s 4 and 5 of your Raspberry Pi.
7) start the the shell script
root@raspberrypi:/usr/local/application# ./applicationloop.shand 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
- 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
All elbfisch modules run on separate threads.
Let’s begin with the elbfisch module TogglePinModule.
/**
* 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.
}
}
In it’s constructor it instantiates an LogicalOutput instance named pin4:
It is addressed by the uri “raspigpio:/4” which is used by elbfisch vioss (versatile input/output subsystem) to locate it.
pin4 = new LogicalOutput(this, "RaspiOutputPin04", new URI("raspigpio:/4"));The main activity is done inside the work() method. It first instantiates the process event PeriodOfTime which can be used by an elbfisch module to delay a certain activity for given amount of time (here 1 second). Then it runs into a loop in which simply toggles the pin every second.
pin4.set(!pin4.is(true));(Every ten’th second the toggle is delayed for another 2 seconds (extendedToggleTime).)
The elbfisch module ReadBackPinModule simply waits for gpio pin#5 to toggle and log’s this event.
/**
* PROJECT : Elbfisch - java process automation controller (jPac)
* MODULE : ReadBackPinModule.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.EventTimedoutException;
import org.jpac.InconsistencyException;
import org.jpac.InputInterlockException;
import org.jpac.Module;
import org.jpac.NextCycle;
import org.jpac.OutputInterlockException;
import org.jpac.PeriodOfTime;
import org.jpac.ProcessException;
import org.jpac.ShutdownRequestException;
import org.jpac.SignalAlreadyExistsException;
import org.jpac.WrongUseException;
import org.jpac.vioss.raspi.gpio.LogicalInput;
import org.jpac.vioss.raspi.gpio.LogicalOutput;
/**
*
* @author berndschuster
*/
public class ReadBackPinModule extends Module{
private LogicalInput pin5;
public ReadBackPinModule(AbstractModule containingModule, String identifier) throws WrongUseException, URISyntaxException, SignalAlreadyExistsException, InconsistencyException{
super(containingModule, identifier);
pin5 = new LogicalInput(this, "RaspiInputPin05", new URI("raspigpio:/5"));
}
@Override
protected void work() throws ProcessException {
Log.info("started ...");
try{
pin5.becomesValid().await();//wait, until the signal pin5 becomes valid
do{
try{
Log.info("pin #5: " + pin5);
pin5.toggles().await(2 * sec);//wait, until pin5 changes it's state
}
catch(EventTimedoutException exc){
Log.info("!!!!!!!!!!!!!! toggle time exceeded !!!!!!!!!!!!!!!!!!!!!");
}
}
while(true);
}
catch(ShutdownRequestException exc){
Log.error("shutting down ... ");
}
}
@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.
}
}
In it’s constructor it instantiates the LogicalInput instance named pin5:
It is addressed by the uri “raspigpio:/5”.
pin5 = new LogicalInput(this, "RaspiInputPin05", new URI("raspigpio:/5"));The main activity is again done inside the work() method. It first wait’s, until the vioss has
read in the pin the first time
pin5.becomesValid().await();and afterwards, in a loop, it wait’s for pin#5 to toggle
pin5.toggles().await(2 * sec);If the toggle does not occur within 2 second’s a EventTimedoutException is thrown.
As pin#4 and pin#5 are shortcircuited, every time the TogglePinModule changes the state of pin#4 the ReadBackPinModule is invoked by the above mentioned toggles event.