LCD 16x2 is blank

Hello  Hans and the community!

I have run into a problem with Joi-IT 16x2 display.
I connected and I think I configured everything right, checked several times.
USE_I2C_LCD  is set to true and I2C_LCD_ADDR is 0x27 (checked it with i2c tools)
The buttons seem to work but the display doesn't give a sign of life besides the glowing backlight. I tried the demo file from the manufacturer to check if the screen is working in general, and it is. Shows the right bitton clicked. So i assume that the problem is with the display wiring.
Can't really find a place in samplebox to change the wiring info to check that option out.

also when I start samplebox from the console I get

Code:

Starting I2C LCD..
Available audio devices:
  0 bcm2835 Headphones: - (hw:0,0), ALSA (0 in, 8 out)
  1 sysdefault, ALSA (0 in, 128 out)
< 2 default, ALSA (0 in, 128 out)
  3 dmix, ALSA (0 in, 2 out)
Opened audio device #0 bcm2835 Headphones: - (hw:0,0)
  samplerate 44100Hz, blocksize=384, LFOcycle=1
  valid blocksizes: [32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384]
Opened Alsamixer: card (hw:0,x), control Headphone
We have None, we want 0 Demo
./modules/buttons.py:36: RuntimeWarning: This channel is already in use, continuing anyway.  Use GPIO.setwarnings(False) to disable warnings.
  GPIO.setup(m[2], GPIO.IN, pull_up_down=GPIO.PUD_UP)
Started 4 GPIO-buttons: BUT_incr=4, BUT_decr=16, BUT_sel=10, BUT_ret=9
Opened input "Midi Through:Midi Through Port-0 14:0" as SMFplayer
Starting httpd on port 80
Loaded '0 Demo', 86% free memory left

(atm I disconnected the sound card and midi keyboard, they work great. Everything besides the screen works great)

is it okay that I get this?

Code:

./modules/buttons.py:36: RuntimeWarning: This channel is already in use, continuing anyway.  Use GPIO.setwarnings(False) to disable warnings.

At the moment I don't know what to do or where to find the solution.
I wrote the manufacturer to get the screen pinout but no answer at the moment, maybe you can help in any way?


Thank you in advance

Hi WhiteTigerMort,
Wiring can't be wrong since it's a hat.
The GPIO error message is normal at the first manual start as stopping the autostarted process is ahrd cancel leaving the GPIO's in use (if you ctrl-C and start the box again it won't show up anymore).
The LCD routine is started without error messages.
So for now as I'm as puzzled as well
..did you leave "USE_HD44780_16x2_LCD = False" as is (=False)
Noek

Hi WhiteTigerMort,
Wiring can't be wrong since it's a hat.
The GPIO error message is normal at the first manual start as stopping the autostarted process is ahrd cancel leaving the GPIO's in use (if you ctrl-C and start the box again it won't show up anymore).
The LCD routine is started without error messages.
So for now as I'm as puzzled as well
..did you leave "USE_HD44780_16x2_LCD = False" as is (=False)
Noek

Thank you for your fast answer.



Yeah, it is set to false. I tried different variants. Will include my configuration.txt bellow

UPD:
The manufacturer sent me the pinout, but i can't see anything wrong. They use 3,3V, 5V, GNG, SDA, SCL and also added the pinout image, will attach it also if it helps

UPD2:
On the manufacturers github they mentioned

This library is based on the CircuitPython_LCD library by dhalbert. The changes were necessary because of a different pinout used with the PCF8574 and a HD44780.

 Could this be the source of the problem?

Hi both,
Hmm, I don't quite get it as well...
The I2C_LCD option uses a PCF8574 interface. This indeed translates the HD44780 pinout to an I2C pinout.
I couldn't find any more on the manufacturers site or the github code regarding more differences.
There is one potential cause in the code.
Can you try "USE_I2C_LCD = 16x2" instead of "USE_I2C_LCD = True" ?
Regards, Hans

Hi both,
Hmm, I don't quite get it as well...
The I2C_LCD option uses a PCF8574 interface. This indeed translates the HD44780 pinout to an I2C pinout.
I couldn't find any more on the manufacturers site or the github code regarding more differences.
There is one potential cause in the code.
Can you try "USE_I2C_LCD = 16x2" instead of "USE_I2C_LCD = True" ?
Regards, Hans

Hey, yeah, I've tried that too, no change.

Oh well, thanks a lot guys, if this doesn't work I will just go get myself Pirate Audio Line out and will take apart this screen and use it in some Arduino project.
really wanted this to work, bit seems to be something wrong.

But will install a clean image, and try again one more time. Will let you know if it changes anything.

Hi both,
Hmm, I don't quite get it as well...
The I2C_LCD option uses a PCF8574 interface. This indeed translates the HD44780 pinout to an I2C pinout.
I couldn't find any more on the manufacturers site or the github code regarding more differences.
There is one potential cause in the code.
Can you try "USE_I2C_LCD = 16x2" instead of "USE_I2C_LCD = True" ?
Regards, Hans

Hey, yeah, I've tried that too, no change.

Oh well, thanks a lot guys, if this doesn't work I will just go get myself Pirate Audio Line out and will take apart this screen and use it in some Arduino project.
really wanted this to work, bit seems to be something wrong.

But will install a clean image, and try again one more time. Will let you know if it changes anything.

Hi! I had a similar problem with my LCD too, althou its a diferent model. I had to format the SD card and save the image again, after double check all files were ok, it worked. Also, someone said a bad cable could cause that problem, so replacing the wires worth a try. Good luck!