OLED issue with long wires.

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Leon
 

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Joined: 25 May 2022, 08:41
Location: Barcelona
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OLED issue with long wires.

Post by Leon »

Hello!

Firstly I want to compliment Manuel and Guido for such an impressive Work. Sharing your project to the World in such a way is only something Radioamateurs will do, and we are proud of it. And yes, radioamateurs can’t help to tinker… that is why I decided to make some modifications to the initial setup, but having the screen a few inches away from its original place.
This has produced some side effects on the reliability of the Oled screen. Whereas with standard position or with 4cm cable it was ok.

My test have been made using a 15cm length wire. Symptoms:
  • Occasional misalignment of characters
  • Vertical lines
  • Character size changes
  • Reversed orientation
  • Glitches
  • Nothing on the screen
This behavior is held specially when interacting with the encoder
Powered by usb or 12V

I have tested with a screened wire with no success.

I see it is a common problem with I2C protocol… Some people shared this issue here https://forum.arduino.cc/t/128x64-oled- ... ion/610179

I will do more tests
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DL2MAN
 

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Joined: 30 Dec 2021, 19:18
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Re: OLED issue with long wires.

Post by DL2MAN »

Hello,

I saw your postings about this issue on facebook, and I didn´t want to interfere, as my opinion might be received "narrow minded".

But since you came here and asked directly, I will give my Opinion:

(tr)uSDX was created as a standard hardware, that is known to work, when built and assembled in the presented form. Once you deviate from that, you should know what you´re doing, as you´re on your own.
We´ve overcome a lot of obstacles to make that OLED work in that circuit reliably and without Noise, so any deviation from Standard Setup is up to you.
Again: (tr)uSDX is supposed to be a solid standard, so we won´t encourage you to deviate from that standard, especially if you´re asking for support. CC-BY ND License stands for No Derivates, however, since you´re only doing it for yourself it does not apply here. But it shows well my intentions : Don´t change it, if you want it to work !
It was never meant to be connected through wires.

Feel free to exchange ideas with others here and on facebook, but my support on this will be limited to this very posting.

73 Manuel; DL2MAN
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Leon
 

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Joined: 25 May 2022, 08:41
Location: Barcelona
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Re: OLED issue with long wires.

Post by Leon »

Thank you Manuel. I didn't expect official support. I am just looking for some answers, or in the worst case, showing what happens with long wires.

In any case I hope I am not the only one that experiments with the unit
AC9YY
 

Posts: 133
Joined: 21 Mar 2022, 00:04
Location: Illinois, USA

Re: OLED issue with long wires.

Post by AC9YY »

If you have access to a good oscilloscope it could be revealing as to what the issue is.
DL3MHT
 

Posts: 21
Joined: 14 Mar 2022, 09:46

Re: OLED issue with long wires.

Post by DL3MHT »

I agree, check the I2C signals with a scope. Maybe also check the pull-up resistors on the OLED display.
Was everything working perfectly fine when the display was still soldered onto the board?

My 2 cents would be that 15cm cable on an I2C display should work if you don't pickup any RF or radiate noise to your RX.

(I used more than 40cm unshielded wire once to drive the 128x32 pixel version of that OLED display with the same controller for a different project without issues. Well the whole thing was sitting in a full metal case, was not a TRX and had the benefit that you could use double-buffering with the smaller display variant.)

Anyways, if your signals look fine, maybe use a shielded wire for SDA/SCL at least... A few cm of old stereo headphone/headset audio cable might improve things.

-Tobias
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Leon
 

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Location: Barcelona
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Re: OLED issue with long wires.

Post by Leon »

I am still on the ring looking for solutions.
I have placed a 1000uF between Vcc and GND. Now it is much more stable and reliable but it does have glitches. This thing definitely needs some filtering
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