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

jayel · Feb 22, 2016

When I try to run in debug mode I get a error and the program stops : unable to open SPI device.

Any ideas?

John

Mark Turney · Feb 22, 2016

Silly question probably, but did you enable SPI in raspi-config?

jayel · Feb 22, 2016

Mark Turney said:
Silly question probably, but did you enable SPI in raspi-config?

there no silly questions, just silly answers .... it worked, thanks

Herbert32 · Feb 23, 2016

actual Version ?

in first Thread i see 1.50

but here i see 1.60

which information is true ? if second, where can i download?

thx in advance

Erel · Feb 23, 2016

v1.60 is available here: https://www.b4x.com/android/forum/threads/raspberry-pi-resistor-sensor-reading.63557/#post-401933

It adds an option to switch a pin from input to output and vice versa.

jayel · Jun 2, 2016

Hey,

Can this be used ? http://www.piface.org.uk/guides/Using_the_PiFace_Rack/Addressing_multiple_PiFace_Digitals/

I want to be able to read more than 8 inputs.

I suppose it has something to do with this line ? :

B4X:

controller.InitializePiFace(0x40, 0)

John

Erel · Jun 2, 2016

It should work based on this solved issue: https://github.com/Pi4J/pi4j/issues/131

Pass 0x42 or 0x44 or 0x46 for the SpiAddress and pass 1 for the channel.

jayel · Jun 5, 2016

Hey,

Strange :

B4X:

pin5.Initialize("pin5",5)
    pin5.SetPinPullResistance("PULL_DOWN")
    pin5.Name = "Detectie binnen-buiten"
    jo = pin5
    jo.RunMethod("setDebounce", Array(25))

I get this error :

Waiting for debugger to connect...
Program started.
Error occurred on line: 196 (Main)
com.pi4j.io.gpio.exception.UnsupportedPinPullResistanceException: This GPIO pin [INPUT 6] does not support the pull resistance specified [down]
at com.pi4j.gpio.extension.piface.PiFaceGpioProvider.setPullResistance(PiFaceGpioProvider.java:429)
at com.pi4j.io.gpio.impl.GpioPinImpl.setPullResistance(GpioPinImpl.java:189)
at anywheresoftware.b4j.objects.GpioControllerWrapper$GpioPinDigitalWrapper.SetPinPullResistance(GpioControllerWrapper.java:75)
at b4j.example.main._initinputsoutputs(main.java:235)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:612)
at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:226)
at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:159)
at sun.reflect.NativeMethodAcces
sorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:93)
at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:90)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:84)
at b4j.example.main.main(main.java:29)

PULL_UP works???

Why doesn't PULL_DOWN work ?

Greets

John

Erel · Jun 5, 2016

I have nothing to add over the error message. It seems like this pin doesn't support pull down. For further discussion please start a new thread.

coslad · Jul 31, 2016

Hi, new 1.1 version is released:

Added support for Raspberry Pi 3 - Model B

Please upgrade the wrapped library to support RPI 3

Thanks

Erel · Jul 31, 2016

Raspberry Pi 3 is already supported. Did you encounter any error?

coslad · Jul 31, 2016

No, not error , but in the highlights is written : Added support for Raspberry Pi 3 - Model B

And I thought were some update.

jinyistudio · Nov 16, 2016

Hi

Which jar does i need to download(include) if i want to use following code to access SPI ?

Erel said:

Try this code:

B4X:

Sub WiringPiSPISetup(Channel As Int, Speed As Int) As Int
   Dim jo As JavaObject
   Return jo.InitializeStatic("com.pi4j.wiringpi.Spi").RunMethod("wiringPiSPISetup", Array As Object(Channel, Speed))
End Sub

Sub WiringPiSPIDataRW(Channel As Int, Data() As Byte, Len As Int) As Int
   Dim jo As JavaObject
   Return jo.InitializeStatic("com.pi4j.wiringpi.Spi").RunMethod("wiringPiSPIDataRW", Array As Object(Channel, Data, Len))
End Sub

Make sure to go over the documentation: http://pi4j.com/apidocs/com/pi4j/wiringpi/Spi.html

Erel · Nov 16, 2016

You don't need to add any other jar. Only this library.

jinyistudio · Nov 24, 2016

I try following to access spi in PI but it always return 12 to me !? OK or Not ok !?

B4X:

Sub WiringPiSPISetup(Channel As Int, Speed As Int) As Int
   Dim jo As JavaObject
   Return jo.InitializeStatic("com.pi4j.wiringpi.Spi").RunMethod("wiringPiSPISetup", Array As Object(Channel, Speed))
End Sub

Sub WiringPiSPIDataRW(Channel As Int, Data() As Byte, Len As Int) As Int
   Dim jo As JavaObject
   Return jo.InitializeStatic("com.pi4j.wiringpi.Spi").RunMethod("wiringPiSPIDataRW", Array As Object(Channel, Data, Len))
End Sub

Erel · Nov 24, 2016

Please start a new thread for this question.

rbghongade · May 24, 2017

Dear Erel,
It seems the library is not compatible with Raspberry Pi Zero W. Maybe pi4J library at http://pi4j.com is not updated. I get the following error message:;

B4X:

Unable to determine hardware version. I see: Hardware    : BCM2835
,
- expecting BCM2708 or BCM2709. Please report this to projects@drogon.net

Let us hope this problem is sorted out.
Just reporting.

rwblinn · May 24, 2017

Answer related to Post#137.
Hi,

also stumbled recently about this issue. After various testing (based on thread discussions), resolved by [status 20170506]:

Reinstalling wiringPi on the Raspberry Pi - see http://wiringpi.com/download-and-install/ .
Checked the wiringPi version using command "gpio -v", resulting in 2.44.
Installed the Pi4J snapshot library files (pi4j-1.2-SNAPSHOT.zip) from http://pi4j.com/download.html in the B4J Additional Libraries folder: Copied from the snapshot bin folder, the jars pi-core, pi-device, pi-gpio-extension.

Note: To check the RPi CPU use command "cat /proc/cpuinfo". See at the bottom under hardware ie hardware : BCM2835.

Ilya G. · Jun 1, 2017

Not working on Linux 4.9.24-v7+

B4X:

Unable to determine hardware version. I see: Hardware   : BCM2835
,
- expecting BCM2708 or BCM2709.

To rwblinn, after updating pi4j-core, pi4j-device, pi4j-gpio-extension doesn't work with jDHT library

rwblinn · Jun 1, 2017

GanjaKyp said:
Not working on Linux 4.9.24-v7+

Thanks for the info. I can not verify as do not have Linux 4.9.24-v7+ - can only test on a RPi.
Note: Tested jDHT 1.0 again with success under Raspbian GNU/Linux 8 (jessie) with hardware BCM2835 (RPi 3) & DHT11 - just to go for sure.

B4J Library [IoT] jPi4J - Raspberry Pi GPIO controller

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