Java and I2C Display

[dbrazzor]

Hello!

I recently bought a LCD display (HD44780 - 1602 - 16x2) and a I2C module that should allow me to save some precious pins on the Pi, it runs with a PCF8574T chip, this one looks like this :



I found a lot of Python scripts that worked almost perfectly (http://www.raspberrypi-spy.co.uk/2015/0 ... pberry-pi/ for example), but not any Java one. At least not for this chip

Does anyone know how to achieve it? or have some tips? I would really appreciate it.
Thanks in advance!

dbrazzor

[mattlewis]

Depends which Java library you were to use. You could of course use the diozero library which adds an abstractoin layer across the various options (Pi4j, pigpio, wiringPi, JDK Device I/O) .
I've just pushed up a snapshot build (0.7-SNAPSHOT) with a port of the Python code to Java as an example. I don't have one of those devices hence haven't been able to test this.

Matt

[dbrazzor]

Thanks Matt!

I've never used the diozero library before, I was happy with PI4J
I installed it but I got the following error :
"Error: no device provider factory service found, please configure META-INF/services/com.diozero.internal.spi.NativeDeviceFactoryInterface or set -Dcom.diozero.devicefactory".

Also, in the I2CLcd class you've made, the method

Code: Select all

writeByte(byte)

does not exist, I replaced it with

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writeByte(DEVICE_ADDRESS, byte)

I don't know if I was expected to do it this way, I am completely new with I2C, sorry about that

I hope I can get some help, thanks again!

[mattlewis]

Apologies for the confusion - I pushed a new snapshot build to sonatype but not google drive. I've just uploaded 0.7-SNAPSHOT Zip file to google drive. If you extract that zip file you should be able to run the following:

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sudo java -cp tinylog-1.0.3.jar:diozero-core-0.7-SNAPSHOT.jar:diozero-provider-pi4j-0.7-SNAPSHOT.jar:pi4j-core-1.1-SNAPSHOT.jar com.diozero.sandpit.I2CLcdSampleApp

Let me know if this works, I'm keen to get feedback on diozero, the aim of it is to make life much easier to develop Java apps on the Pi.

If you're familiar with Pi4j it also has support via its com.pi4j.component.lcd.impl.I2CLcdDisplay class in the pi4j-device JAR.

Regards,
Matt

[dbrazzor]

Thanks again, but I can't find the link to your Drive (Or am I just exhausted?)

I already saw the PI4J I2CLcdDisplay class but I can't figure out some values, like rs, rw, d4 ➔ d7.

Really appreciate the help

dbrazzor

[mattlewis]

Does this link work? https://drive.google.com/folderview?id= ... kd4OXhYd3c.
There's also a link from the docs at http://rtd.diozero.com/.

[dbrazzor]

I tried the command but got the following error : http://pastebin.com/fpZvjRmu

The log file : http://pastebin.com/czjTyqWM

Thanks for the help!

dbrazzor

[mattlewis]

Strange - that's an error loading the Pi4j shared library. What Pi are you running this on? I've just tried running this on a Pi 2 and a Pi Zero and got the same error as you on the Pi Zero but only when using the Pi4j provider.
Can you try with the pigpio provider please using this command:

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sudo java -cp tinylog-1.0.3.jar:diozero-core-0.7-SNAPSHOT.jar:diozero-provider-pigpio-0.7-SNAPSHOT.jar:pigpioj-java-1.0.0.jar com.diozero.sandpit.I2CLcdSampleApp

I've noticed that this occasionally fails (with a signal 11) on the Pi Zero but then works if I try again, I need to debug to get to the bottom of this.

Regards,
Matt

[dbrazzor]

I am running it with a Pi model 1 - B+.

I tried the command, it gives me some infos and turn of the display's backlight off but nothing else (http://pastebin.com/ZJDjtJ74).

Regards,
dbrazzor

[mattlewis]

Getting closer . Does the Python code linked to at the start work? I tried to replicate it exactly in Java...
I might look in to buying one of these, in the meantime you could try pull the diozero code from GitHub and try get it working - I can commit any changes you make.
Happy to answer any questions regarding setting up a dev environment.
Actually I did fix a stupid bug in the lcd driver class (when calling the string pad method!) that meant it would always display spaces, I may not have updated the Google drive zip file afterwards. Will update tomorrow.

Matt

[mattlewis]

As promised uploaded a new distribution ZIP file to Google drive.

Hope this works, I've ordered one of these so will be able to test and improve when it arrives.

Regards,
Matt

[dbrazzor]

Hello, thanks a lot but I don't see any new distribution on your Drive :c
Have you received the display? Hope you'll enjoy it

[mattlewis]

I updated the existing 0.7-SNAPSHOT ZIP file.

Display arrives tomorrow.

Regards,
Matt

[dbrazzor]

Haw okay, I tried this distribution again but got the same results

dbrazzor

[mattlewis]

Apologies for the delay, busy with work and a birthday weekend
Just had a quick test and it is working with my setup (lost a lot of time thinking it wasn't working until I tweaked the display contrast!). I've pushed a new snapshot build to Google drive plus commited modified code to GitHub. Still needs tidying up plus can be made a bit more generic to work with other setups (not all of these I2C connected LCDs are wired the same apparently).

Let me know if this works for you, fingers crossed.

Regards,
Matt

[dbrazzor]

Hello! No worries, Happy birthday!

I have to say, you made my day! Your code works with my setup, I've been searching for something like this for weeks!

Here is a video of the code running on my display :
https://drive.google.com/open?id=0BxgwY ... kdnSFUzekE

Can you explain me how should I implement this in my project?

Thanks a lot for what you've done

(I thought I had received a bad unit because of the contrast too ^^')

[dbrazzor]

When I use the following code (found in I2CLcdSampleApp) :

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I2CLcd lcd = new I2CLcd(16, 2);
        lcd.setText(0, "Welcome!");

I got the following error :
http://pastebin.com/yTx6zm9y

(Sorry for the multiple posts and the inconvenience)

[mattlewis]

Excellent news, glad you've got it working. I'm using the 1.1-SNAPSHOT version of Pi4j, I'm not at my computer now but it looks like you may be using an older version of Pi4j that doesn't have the method that I'm using. For info I do most testing using my pigpio provider.
Nice looking project by the way!
Matt

[dbrazzor]

Hello Matt, thanks for your help!

I just tried with PI4J 1.1 (Sorry, I was busy with school projects ), It works pretty well, but sometimes I got some weirdness going on :




Also, the text disapear for no reason (at 24s) :

https://www.youtube.com/watch?v=WUMHevmHsFQ

Oh and the audio is affected by it, at random moments the sounds just stop. Even when it's played outside the program (??).

Regards,
dbrazzor

[mattlewis]

Is your code on GitHub? Happy to take a quick look...

Regards,
Matt

[dbrazzor]

Hello!

I am currently recoding it, I will put it on Github

Regards,
dbrazzor

[kendler]

can you please share what values should be in d4->7 bits?

Nevermind, found it
new I2CLcdDisplay(4,20,1,0x27,3,0,1,2,7,6,5,4); is the way.

[Pawel_G]

Hello,
First of all Matt, I just want to say thank you for shering your library, it looks really promissing, great job!

Guys, I'm new with raspberry pi and I2C stuff, and I've got a problem with I2C addressing, it looks that my I2C converter actually got 3f address, but I2CLcd class constructor takes only int as address parameter, do you know what should I type there to run I2CLcdSampleApp20x4?

[DougieLawson]

it looks that my I2C converter actually got 3f [sic] address,

0x3f hex == 63 decimal substitute that for 0x27 hex (or 39 decimal) wherever you see it in the sample code you're working with.

[mattlewis]

The latest version of the I2CLcdSampleApp20x4 allows you to specify the I2C address as well as the I2C bus number. The I2C address parameter is parsed using Integer.decode so can accept decimal, hexadecimal, and octal numbers.

Matt