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Thread: Garbled LCD screens
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05-26-2015, 07:10 PM #1
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- May 2015
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- 3
I don't really think that the screen get garbled due to timings or ESD.
I never supposed that anybody could connect something directly to an MCU pin with a half-meter wire, but they did it... And that single thin GND wire (yep, only one of 20 wires is a GND) only aggravates the situation.
This garbling issue can be fixed by adding a serial resistor to each MCU output connected to the LCD. These resistors should be placed as close as possible to the signal source (i.e. to the MCU in our case case) and by routing a reliable ground wire to the LCD board.
But I'm to lazy to do all these things, so I've just cut the LCD cable (there are two cables - one for LCD and power, and another one for SD card) at the mainboard side and solder 47 Ohm resistors there. This appears to be enough to get rid of LCD screen garbling.
lcd1.jpg
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05-27-2015, 12:33 PM #2
Interesting. Be sure to report back after a while to confirm whether or not the series termination resistors solved your garbled display problem. I'd try the fix myself, but I've eliminated the nibble transfer display as part of migrating to Smoothieboard on my i3v.
Technically, the bulk of the benefit is likely obtained by adding the termination resistor in the E signal line to the display. IIRC, that is the signal that is pulsed to latch each nibble data transfer into the display module. Ringing on any other pins likely wouldn't matter as long as they're stable when the E pin is pulsed, but there's no reason the termination can't be added in all the data lines. Also note that some of the data lines (encoder, SD reader) on the two cables are driven by the smartpanel and not the ATMEGA2560.
I don't really think that the screen get garbled due to timings or ESD.Last edited by printbus; 05-29-2015 at 11:24 AM.
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01-03-2018, 03:15 AM #3
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- Jan 2018
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- 1
Printbus and ESS, I cannot say thanks enough to you both. I had already shielded the LCD ribbon of my ANET A8 but the screen still failed once every 3 min or so. I then installed only one 47 Ohm resistor directly on the LCD PCB in serial of the ENABLE signal and combined with the shielding connected to ground, it's now working very very well.
I have not yet the feedback over a long print but definitely it helps a lot.
But ENABLE+47Ohm alone or shielding alone is not enough (for me)
ANET_LCD_solution.jpg
Please explain to me how to...
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