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Garbled LCD screens

Posted by RRuser 
Garbled LCD screens
November 12, 2015 06:45AM
Especially on versions with the SD card attached. Anyone figured out what conditions cause this?
Re: Garbled LCD screens
November 12, 2015 07:14AM
What FW? What HW? How connected? A picture?

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Re: Garbled LCD screens
November 12, 2015 10:46PM
Well I was looking for general ideas, but mine is a prusa i3 with marlin 1.0.3 with this lcd...

The ribbon cables are separated out by themselves, way away from almost everything. I've jiggled the cables, connectors, controller, lcd, and banged on the frame, but cannot make it happen. It just garbles by itself, usually on the second layer, and then further up.

I'm trying new SD cards now.
Re: Garbled LCD screens
November 13, 2015 12:54AM
ribbon cables are crap

Make sure they are really short or use real cables like this eg [www.mini-kossel.com]

Edited 1 time(s). Last edit at 11/13/2015 12:54AM by Dust.
Re: Garbled LCD screens
November 15, 2015 11:40AM
I'll try that cable. Also order a ferrite ring that clamp around the ribbon.

The garbling has only been recent, however. So something is changing, causing more of it. Also, the extruder now is making random travels in X or Y, then going back to print properly. Probably also a cable/interference issue.
Re: Garbled LCD screens
November 15, 2015 12:01PM
Mine has been doing that from the start, also a 20x4 character display. Never had it with the ones I used in my PIC16F microcontroller projects, usually 16x2 LCDs. It could be a power pulse from the PC or PSU. It could also be that the enable is set low or read/write line isn't set high so that any pulses on the data lines aren't ignored.

It could be that the motor currents are leaking into the 5V line. Those pulses sure will cause such behavior. Some decoupling capacitors might also help, a 0.1uF ceramic and 10-100uF electrolyte between the GND and +5V lines.
Re: Garbled LCD screens
November 15, 2015 12:07PM
Good suggestions.
See also this thread.

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Re: Garbled LCD screens
November 17, 2015 07:53PM
I had nothing but problems with LCDs that were connected via a parallel interface. I have since swapped out with a serial LCD using the panelolu2 and the difference is night and day. I have had absolutely NO garbage on the screen since making the change.

I doubt that you can find a retailer selling panelolu2 - so it's in the domain of the do-it-youselfer. I had to use the eagle files to fabricate my own boards via oshpark, so it was a bit of work.
Re: Garbled LCD screens
November 18, 2015 02:46AM
Thanks for the tip! It doesn't bother me, pressing the control knob clears it up for me.

Kind regards

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Re: Garbled LCD screens
November 18, 2015 01:47PM
I traced my problem down to static in the air and bad grounding. It had nothing to do with the ribbon cables. I simply grounded the knob encoder (metal part) to my psu and it never happened again.

This was an issue when I was printing in my apartment when the heat was on causing very very dry air.

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Re: Garbled LCD screens
November 20, 2015 07:00AM
Fixed. My solution was to put a ferrite ring around the cables.
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