B4J Library [IoT] jPi4J - Raspberry Pi GPIO controller

Erel · Feb 5, 2014

Updated libraries: https://www.b4x.com/android/forum/threads/pi4j2-raspberry-pi-i-o-library.136113/#content

This is a wrapper for Pi4J library.
It allows you are control the Raspberry Pi board GPIO pins.

Using this library is quite simple. You can use it from a UI app or non-UI app.

First you should initialize a GpioController object.
The second step is to initialize one or more pins.

You can provision each pin to be an input pin or output pin. Input pins allow you to listen for state changes. Output pins allow you to set their state.

The following program initializes two pins. Pin1 is an input pin and pin2 is an output pin. Pin2 state is changed every 5 seconds with a timer:

B4X:

'Non-UI application (console application)
#Region  Project Attributes
   #CommandLineArgs:
   #MergeLibraries: true
#End Region

Sub Process_Globals
   Private controller As GpioController
   Private Pin2 As GpioPinDigitalInput
   Private Pin1 As GpioPinDigitalOutput
   Private Timer1 As Timer
End Sub

Sub AppStart (Args() As String)
   controller.Initialize
   Pin1.Initialize(1, True) 'GpioPinDigitalOutput
   Pin2.Initialize("Pin2", 2) 'GpioPinDigitalInput
   Pin2.SetPinPullResistance("PULL_DOWN")

   Log("Monitoring Pin2 state")
   Timer1.Initialize("Timer1", 5000)
   Timer1.Enabled = True
   StartMessageLoop
End Sub

Sub Timer1_Tick
   Pin1.State = Not(Pin1.State)
   Log("Switching Pin1 state. Pin1 state = " & Pin1.State)
End Sub

Sub Pin2_StateChange(State As Boolean)
   Log("Pin2 StateChange event: " & State)
End Sub

The pins scheme is available here: http://pi4j.com/usage.html

The output of this program:

B4J-Bridge is very useful when working with this board: http://www.b4x.com/android/forum/threads/remote-debugging-with-b4j-bridge.38804/
You can download it to the board with this command:

B4X:

wget https://www.b4x.com/b4j/files/b4j-bridge.jar

Then run it as root:

B4X:

sudo <path to java> -jar b4j-bridge.jar

PiFace extension

V1.00 adds support for the PiFace extension: http://www.savagehomeautomation.com/piface

See this post: http://www.b4x.com/android/forum/threads/jpi4j-raspberry-pi-gpio-controller.37493/#post-232767

Download link: www.b4x.com/b4j/files/jPi4J.zip

Erel · Oct 29, 2015

Which OS is running on the device?

MbedAndroid · Oct 29, 2015

raspian.....

Erel · Oct 29, 2015

Are you sure that it runs on the RasPi and not on the PC?

Make sure that the IDE is connected to B4J-Bridge.

You will get this exact error if you run it with B4J-Bridge disconnected (which means that it tries to run it on the PC).

MbedAndroid · Oct 29, 2015

it was connected....
but i will retry as i used SSH. Will try it directly and let you know

Erel · Oct 29, 2015

It doesn't matter whether you use SSH or not.

The IDE should be connected:

Erel · Oct 29, 2015

BTW, you can see from the error message that it ran on Windows and not on Linux:
SEVERE: Unable to load [libpi4j.so] using path: [/lib/libpi4j.so]
java.lang.IllegalArgumentException: The path has to be absolute, but found: \lib\libpi4j.so

The forward slash is only used on Windows.

MbedAndroid · Oct 29, 2015

your're right erel
with sudo java -jar b4j-bridge.jar it works...
thanks !
i think i missed the "connected" message

KMatle · Oct 30, 2015

The RB has 8 digital inputs. With them we can check 8 switches (or even more with more boards).

8 Bits represent 255 different values. For sure there is some hw to convert it but I don't know the word for it. Can someone help?

My idea is to handle up to 255 switches with the 8 inputs.

Roycefer · Oct 30, 2015

I think you're looking for a multiplexer. This will use up some of your digital outputs, as well.

Cableguy · Oct 30, 2015

Search for multiplexer circuits/ ICs. as roycefer stated, some digital pins will be needed to control wich input to use.
for example, a 1 to 16 mux uses 5 digital pins, 4 to select witch of the 16 inputs will be selected.
So for 256 digital I/O you will need 8 control pins and another to retrieve the value.

There may be other ways like cascading Muxes...

You can also check non-traditional multiplexing techniques, like charlieplexing

Michael1968 · Oct 30, 2015

is a
parallel-in/serial-out shift register a solution?

74LV165A as an example

Cableguy · Oct 30, 2015

Alternatively you can use a single analog input to read wich of the 256 switches is pushed.
Read this PDF, specially the tip#5

http://ww1.microchip.com/downloads/en/DeviceDoc/01146B.pdf

KMatle · Nov 8, 2015

Trying to run a 2x16 LCD display over my piFace 2 (via digital outputs). It has a serial in.

I use these pins:

PinFunction
1Ground
2Positive 5 volt
3VEE (Connect to +5 and GND through 10k Pot for display contrast)
4RS (Low for command - high for characters)
5RW (Low for write - high for read)
6E (Toggle to load data and command)
7-14Data pins
15Backlight +
16Backlight Ground

As I've understood by setting #6 from low to high and back the data is writen to the display.

I try it with this code by setting the outputs:

B4X:

Select seq
        Case 1
            e.State=True
            seq=seq+1
        Case 2
            d4.State=True
            d5.State=True
            d6.State=False
            d7.State=False
            rs.State=False
            rw.State=False
            seq=seq+1
        Case 3
            e.State=False
            seq=seq+1
        Case 4
            e.State=True
            seq=seq+1
        Case 5
            d4.State=True
            d5.State=True
            d6.State=False
            d7.State=False
            rs.State=False
            rw.State=False
            seq=seq+1
        Case 6
            e.State=False
            seq=seq+1
        Case 7
            e.State=True
            seq=seq+1
        Case 8
            d4.State=False
            d5.State=True
            d6.State=False
            d7.State=True
            rs.State=False
            rw.State=False
            seq=seq+1

The code is crap but I wanted to try it. It's called by a timer (0,5secs). Am I totally wrong here or is it the right direction?

Mark Turney · Nov 8, 2015

If no one else beats me to it, I'll try the same setup tomorrow and let you know what I get.

Mark Turney · Nov 10, 2015

I just had a chance to solder wires to my 2x16 LCD. Will experiment a bit tonight and tomorrow.

Mark Turney · Nov 10, 2015

I just realized that I'm not sure what you're trying to display, but I at least got mine to come on. Haven't soldered in quite a while ... forgot how good the fumes smell. LOL ...

Can you post the full code? If you don't want it public, just send me a private message and I will test for you. Thanks!

KMatle · Nov 12, 2015

Mark Turney said:
I just realized that I'm not sure what you're trying to display, but I at least got mine to come on. Haven't soldered in quite a while ... forgot how good the fumes smell. LOL ...

Can you post the full code? If you don't want it public, just send me a private message and I will test for you. Thanks!
View attachment 38788

See here: https://www.b4x.com/android/forum/threads/solved-iot-raspberry-wiringpi-b4j-lcd-2x16.60252/

It's all about the mapping. Take a look to the table (GPIO2 is not always PIN2). The working code is included.

PS: Your display isn't conncected (except power) Maybe this will not work...

Mark Turney · Nov 12, 2015

Ha ha ha on the "connections" comment .... for just a split second, I was going to clarify the pic until I realized that you were kidding ....

HARRY · Nov 20, 2015

Hi,

I am starting a project to communicate from my Raspberry with a I2c device. Starting point is the example by Erel in one of the posts in this thread. I think I am doing something totally wrong, but do not know what. I am not familiar with java objects. The program, up to now looks like

B4X:

'Non-UI application (console / server application)
#Region  Project Attributes
    #CommandLineArgs:
    #MergeLibraries: True
#End Region

Sub AppStart (Args() As String)
   
End Sub


Sub Process_Globals
    Dim bus As JavaObject = GetBus(1)
    Dim device As JavaObject = GetDevice(bus, 0)
End Sub

'Bus methods
Sub GetBus(BusNumber As Int) As JavaObject
   Dim factory As JavaObject
   Return factory.InitializeStatic("com.pi4j.io.i2c.I2CFactory").RunMethodJO("getInstance", Array As Object(BusNumber))
End Sub

Sub GetDevice(bus As JavaObject, Address As Int) As JavaObject
   Return bus.RunMethodJO("getDevice", Array As Object(Address))
End Sub

Sub CloseBus (bus As JavaObject)
   bus.RunMethod("close", Null)
End Sub

'Device methods
Sub Read(device As JavaObject) As Int
   Return device.RunMethod("read", Null)
End Sub

Sub Read2 (device As JavaObject, Buffer() As Byte, Offset As Int, Size As Int) As Int
   Return device.RunMethod("read", Array As Object(Buffer, Offset, Size))
End Sub

Sub Write(device As JavaObject, b As Byte)
   device.RunMethod("write", Array As Object(b))
End Sub

Sub Write2(device As JavaObject, Buffer() As Byte, Offset As Int, Size As Int)
   device.RunMethod("write", Array As Object(Buffer, Offset, Size))
End Sub

When I do Compile and Run, I get a message:
B4J version: 3.70 BETA 1
Parsing code. Error
Error parsing program.
Error description: Parameter name cannot hide global variable name.
Occurred on line: 27 (Main)
Sub CloseBus (bus As JavaObject)

and in the log:
7* Parameter name cannot hide global variable name "
and the text 'unused variable name 'device'

What am i doing wrong?

Harry

Roycefer · Nov 20, 2015

You have global variables called "device" and "bus" and you also have parameters for subs called "device" and "bus". This isn't permitted. Either change the name of the global variables or change the name of the parameters.

B4J Library [IoT] jPi4J - Raspberry Pi GPIO controller

B4X founder

Well-Known Member

B4X founder

Well-Known Member

B4X founder

B4X founder

Well-Known Member

Expert

Well-Known Member

Expert

Active Member

Expert

Expert

Active Member

Active Member

Active Member

Expert

Active Member

Active Member

Well-Known Member

Similar Threads

Privacy & Transparency

Privacy & Transparency