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I found an old LCD in my pile of trunk. I would like to be able to use it. However, someone (possibly / probably me) sawed off the part of the PCB with the series code, so I can't know what the controller chip is. I'm trying to figure it out.

enter image description here

enter image description here

My analysis so far:

The display has backlight. There are 16 pins, so HD44780 would be my first guess (3 power pins, 11 data pins and 2 for backlight). The three pins that are wired up could be power, looking at the traces, and the last two LED anode and cathode. So I tried to wire it up with pin 1 to 0V, pin 2 to 5V, and pin 3 (probably contrast) to 0V. I got this result:

enter image description here

This looks like HD44780 to me, with a 2x16 screen.

But I've got a few questions about this:

  • Are there other (not HD44780-compatible) displays that would give this display when only power is supplied (but no controls), or is this specific for HD44780?
  • The pinout I have used up to now for all LCDs with HD44780 I've used so far (as far as I can remember) had a pinout like this:

    • Power (Vss, Vdd, Vcontrast)
    • Control (RS (register select, command or data), R/W (read / not write), E (enable)
    • Data (DB0 - DB7)
    • Possibly backlight (Anode, Cathode)

    But is this a standard? Can I assume that this uses the same pins for the same functions? And, if not, is it safe to just try it, or could things go wrong? If it could go wrong, is there a way to say judging by the PCB traces what lines would be data, probably?

I don't think it's important, but in the end I intend to use this chip with a PIC. I have used HD44780 displays with PIC before, so I have working code to try out (and also other displays with HD44780 (or ~compatible) to check the code and setup).

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    \$\begingroup\$ Pinout varies by manufacturer. \$\endgroup\$ – Passerby Oct 12 '14 at 21:51
  • \$\begingroup\$ Just try it. 99.9% chance it will work. The 1x14+2 pinout is a defacto standard, and you can't hurt anything if you get the power right and only use +5/0V. \$\endgroup\$ – Spehro Pefhany Oct 13 '14 at 2:00
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Are there other (not HD44780-compatible) displays that would give this display when only power is supplied (but no controls), or is this specific for HD44780?

This is not specific for the HD44780 or similar controllers, but as a matter of fact most character lcds are HD44780 compatible. You can take it for granted.

The pinout I have used up to now for all LCDs with HD44780 I've used so far (as far as I can remember) had a pinout like this snip But is this a standard?

A defacto standard, there can be variations, but again, market forces have consolidated that 14/16 pin straight header as pinout. There is also the Dual Inline pinout.

Can I assume that this uses the same pins for the same functions? And, if not, is it safe to just try it, or could things go wrong? If it could go wrong, is there a way to say judging by the PCB traces what lines would be data, probably?

Based on the looks, yes, go ahead it should work. You already verified the power pins, and the backlight pins. The rest look like datalines into the Chip on Blob. They are all Thin, with no caps or resistors on them.

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If it looks like an HD44780 and it smells like an HD44780 then in all probability it is an HD44780. Yes, there are other display chips, but they are few and far between. Most people just stick to what is cheap and easy to use, which means HD44780.

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I'm almost certain that I saw a character LCD just like that in the past. That made me think that this might be a more a less standard module. Google's image search had discovered several.

On a different note. Judging from the photos in the O.P., a portion of the PCB broken off. That may present problems for reverse-engineering.

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  • \$\begingroup\$ From the looks of it, its just the mounting holes/edge of the board, nothing carrying any signal except maybe ground. \$\endgroup\$ – Passerby Oct 12 '14 at 21:51
  • \$\begingroup\$ Yeah, it looks like it's just that, and a serial number... The second one looks very likely. I didn't check dimension yet, but I used to buy sometimes from VOTI, and it looks exactly the same. \$\endgroup\$ – Keelan Oct 13 '14 at 6:24
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Since you've already got power/ground/contrast mostly sorted out and - from your top photo - pins 15 and 16 are obviously power to the backlight, the heavy hitting's done and all that's left is data and control.

Since the controller is COB, I don't know of any way to visually tell the difference between data and control lines, but since the ,worst that could happen if you got any/all of them mixed up is a garbled display or no display, that wouldn't harm anything.

You can assume anything you want, but in the end the proof is in the pudding, so the answer to all your questions is, basically, "Hack at it until you get it right."

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