Help with new build - OLED not working

[RadioTransparent]

Hi,

I'm having trouble getting my PreenFM2 up and running.  It's a kit from Van Daal Electronics that I built over the weekend.

I followed all of the instructions, including the Yellow OLED high frequency solution (http://ixox.fr/forum/index.php?topic=69159.0), clipping the pin and adding the jumper. I added the 22 Ohm resistor at the spot in the upper right of the board indicated.  Unfortunately, I didn't realize I had the R5d version of the board.

When I started it for the first time, the OLED display flickered, was dim in places and there was high frequency noise.  But, I could navigate the menus, generate random patches, and play notes via MIDI.  The encoders, volume, and LEDs were all functional.

I thought no problem, I'll remove the accidental fix and I should be set.  I desoldered the jumper and replaced the clipped pin.  But then the loading screen would appear briefly (<1 sec) and then go blank.  By pressing the MENU button, I could get something to appear. The display did not flicker, but the text was completely garbled. 

I've checked all of the points in the troubleshooting thread (http://ixox.fr/forum/index.php?topic=63509.0) and the values are all the same, with the exception of the marked display pin, which is 4.6V. (Pin 4 is 3.3V). 

I thought it might be an issue with either the header on the board or the OLED.  I delsoldered and replaced the header on the board.  I desoldered/resoldered the header on the OLED.  There didn't appear to be a short between adjacent pins.

I tried to reflash via bootloader, but the behavior is the same, which makes it difficult to navigate.  The bootloader screen appears for <1 sec and disappears to a blank screen.

Any thoughts what might be happening or what else I could try to solve the problem?  For the few minutes I had it up and running, it was nice.  I'm looking forward to spending more time playing with it.

Thanks in advance for your help.

[RadioTransparent]

Here's the back of the board.  I had difficulty with attachments on the first post.  Thanks again.

[Xavier]

Hi,

That really looks like a bad connection between the preenF405 and the OLED.
If you already tried to resolder both oled connectors, it can come from the DIP40 socket.

This is something we don't see on your pictures, how is the preenF405 DIP40 socket soldered on the PCB ?

You can try to test continuity with a multi metter between the OLED and the preenF405.

[RadioTransparent]

Hi,

Thanks - appreciate the help where to focus.  Attached is a photo of the PreenF405 DIP40 socket.  What pins on the PreenF405 should I check for continuity against which pins on the OLED?

Is there any chance the PreenF405 is corrupted somehow or would need to be reflashed?

[Xavier]

Have you tried entering the bootloader mode ?
Press a key while switching on the preenfm.

Does it work ? Display driver use a slower timing in the bootloader.
If yes, you can try to reflash a firmware from there.

[RadioTransparent]

Sadly, I see the same behavior in bootloader mode.  I see the bootloader screen for less than a second and then it goes blank. 

I was wondering if it would help to flash the STM32F405 the hard way again? Or, do you think it could be something is wrong with the gpio itself?

I did check continuity between the PreenF405 and the display pins.  Numbering the display from left to right 1-16 and the DIP40 socket from left to right 1-20 top (t) and bottom (b) in the last image I uploaded, I see the following:

display / preen
pin 1 - pin 19 (b)
pin 5 - pin 19 (b)
pin 7 - pin 19 (b)
pin 8 - pin 19 (b)
pin 9 - pin 19 (b)
pin 10 - pin 19 (b)
pin 11 - pin 8 (t)
pin 12 - pin 9 (t)
pin 13 - pin 10 (t)
pin 14 - pin 11 (t)

[Xavier]

I attached the preenfm405 to display schema part.

[RadioTransparent]

Hi,

Thank you - this helps.  I get continuity between all of the points in the schema OLED-DIP40. 

I noticed that by putting the jumper in, I was feeding the 4.6V from pin 2 to 15.  It's labeled 'no connect' in the spec sheet, but could that have an effect?

[Xavier]

I don't understand you last part.
"From pin 2 to 15"
Did you mean "TO pin 2 AND 15" ?
What spec sheet are you talking about ?

pin 2 is not used with OLED display.
And pin 15 is less than 5V because of the 22Ohm resistor. It's OK.
Or the oposite depending on the numbering direction 


My last idea is to double check that there's not shortcut between 2 adjacent pins that would corrupt the data.

[RadioTransparent]

Hi,

I ordered and installed a new OLED display and the unit is now working fine.  So, it appears that the OLED itself was the issue.  I can only explain it by something I did when jumpering the two pins with the R5d resistor in place must have damaged the OLED somehow.

The spec sheet I was referring to was for the New Haven Display: https://www.mouser.com/datasheet/2/291/NHD-0420DZW-AB5-247046.pdf.

Thanks for your patience troubleshooting my problem.  Thanks also for creating and supporting the PreenFM.  I'm looking forward to playing with it.