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LCD driving reverse engineering
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TimB100:
Hello People

I'm trying to reverse engineer a LCD panel. The job is to take an off the shelf balance and replace the main PCB so I can add more functions. Like 232 RF USB etc.

On the board there is the usual "blob" handling the weight conversion and LCD driver. I want to reuse everything except the main PCB, so I will use a pic, HX711 for the weighing. HT1621B for the LCD driving.

The issue I have at this time is trying to work out what the pins are on the LCD.

I have scoped the signals and am getting a variety of wave forms. I took pictures of them (below) I think I can identify the commons and the non driven. But have another 2 that seem odd. 1/2 drive 1/3????

So my question is can you tell what they are? And do you have any pointers to how to use the HT1621B to drive the lCD?

Many thanks

Tim
Lukas:
I had to do the same for the pluto watch project: https://github.com/carrotIndustries/pluto#reverse-engineering-bare-glass-lcd-panels

I couldn't make sense of the drive waveform as well, so I did what's described above. This however requires making a test jig for the LCD panel.

You could also try changing what's on the display and look for waveforms that don't change.
TimB100:


Hi Lukas

Thanks for the post. Is there potentially an issue if I get the common lines wrong? If I wire it up as per what I think then drive the other lines and I get my pins wrong does it go bang?

Cheers

Tim
TimB100:


Hi Lukas

It seems your github post answered my questions. Big thanks!

Tim
amyk:
You can use a current-limited supply to test LCD connections. The segments are effectively capacitors and will draw far less than 1mA. Brief uses of DC will not cause any damage, but long-term may cause electrolytic degradation.
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