Confused between different LCD2004 models

[robmar]

Hello,
After successfully assembling an I3 PRO B kit equipped with the GT2560 board and the LCD2004 controller (white pcb), I've bought a second set of GT2560 and LCD2004 "compatible" controller (this time it came with red pcb) to be employed for an I3 aluminium version I'm planning to build using more accurate mechanical components.
The problem I've encountered is that on the new GT2560 / LCD2004 set the display doesn't work. After a closer investigation, it turns out that the pinout on the two 10-way connectors of the new (red pcb) LCD2004 display I got is not consistent at all with the GT2560 signals. For instance, the LCD connector of the GT2560 shows the power supply on pin 1 (VCC) and pin 2 (GND), while instead the LCD connector of the LCD2004 module is expecting power on pin 10 (VCC) and pin 9 (GND). The new display came with an adapter that transforms the two 10-way connectors to a single-row connector plus a smaller 4+4, but there's no place were I can fit it on the GT2560 board.
I'm completely lost... all the sellers of LCD2004 boards around specify that their modules are fully compatible (just a firmware upgrade, possibly) but I cannot see how a display can be considered "compatible" if the supply pins do not match? And, finally, how can I choose an LCD2004 display model that will be compatible for sure with my GT2560?

Many thanks in advance to anyone able to shed some light on this (at least for me) mysterious issue!
Roberto

[Toy]

Normally LCD 2004 is indeed compatible with GT2560, how do you connect the LCD with your board, can you post a picture?

[robmar]

Hello, as per your request I'm attaching the picture of the connections layout board <> lcd, that's the straightforward standard one (EXP1 to LCD and EXP2 to SD)

20160623_062457.jpg (158.69 KiB) Viewed 33650 times

But, as I told, the problem comes not from the connections, but from a major difference in the hardware of the two LCD2004 boards I have.
If you look at the schematic of the GT2560 http://www.geeetech.com/forum/viewtopic ... 18&t=16259) the supply pins of the LCD connector are 1 (VCC) and 2 (GND)
But since on the new LCD board I got (red pcb, from RepRapDiscount) I wasn't getting the expected voltage from the GT2560, measuring directly across the voltage regulator chip, I analyzed further and found that this particular board, although declared "compatible" has an LCD connector configured in a completely different way.
See the schematic http://reprap.org/mediawiki/images/7/70 ... scount.pdf where the supply pins on LCD connector are pin 10 (VCC) and pin 9 (GND)
No wonder I couldn't find the expected voltage on LCD board !!!
But now, since it is evident now that on the market are present two incompatible versions of the LCD2004, my concern is how to tell in advance, before buying a new one, if the advertised board will be of the first kind (supply pins 1-2) or the second kind (supply on 9-10) since all sellers are declaring them fully compatible, while, at least for what concerns the GT2560 board, they are not.
It is enough to look for a white-pcb display board to get the right one? Still confused...

[Toy]

You are right, the LCD you bought is not compatible with your board, so it's necessary to figure out the the version of the LCD, as far as I know, white PCB and blue PCB is campatible with GT2560 board.

[robmar]

Yes, as long as they don't start changing the solder mask color of the wrong model...
Curiously enough, the vast majority of LCD2004 controllers available around is of the red type, but apparently no one encountered this problem before
I'll do some researching and post the results.

[robmar]

Good news!
've found a decent workaround to fix the LCD2004 incompatibility issue.
Being rather stubborn and don't giving up easily, studying the schematics suddenly it came to my attention the fact that the different pinout on the red board were nothing but the same configuration of the GT2560, only... mirrored! Thus pin 1 = 10, 2 = 9 and so on. Having discovered this, I've cut right away two new openings into the IDC ribbon socket's walls in order to accommodate the female plug reversed by 180°

board.jpg (225.63 KiB) Viewed 33601 times

And then, make it or break it, I've powered the boards and... bingo!

20160624_180426.jpg (188.51 KiB) Viewed 33601 times

So, in the end, it turns out that the same board comes in two versions, being the only difference the orientation of the two 2x5 IDC connectors. Hard to tell where's the logic in it, but the positive fact is that the problem can be easily solved with a pair of clippers!

[shadowcaster]

Thanks a lot!

[Chamarejc]

Hi,
Thanks a lot for your help.
After an half day trying to understand what's happened, your solution solve my problem in five minutes.
Now my LCD runs.

[pochacz]

Hi, i was long time since last post, but i haw similar problem, recently I bought Geeetech Prusa i3 Pro B 2017 model, the LCD is not working ( no beck light or anything on it ) however after spinning the knob i can see led blinks on the GT2560 board so they are connected some way, the only difference between my LCD and the one in that post is that my pcb is green, so my question is will that fix work for me??

[cobraoffroad]

I have the same problem did it you try it and has it worked?