Garbled LCD screens

[printbus]

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.

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.

While ESD may not be the cause in all cases, it definitely played a role on my printer. I'd occasionally see the printer garble the display all by itself, but most of the time it would happen when I'd reach for the knob - especially if a finger wrapped around the panel and touched one of the smartpanel circuit boards. EDIT: And BTW, the Marlin code change mentioned in post #18 even has a comment associated with it that says the change is an attempt to recover from a static hit...

[aeropic]

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.

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