[sdiy] LCD hot rodding

Benjamin Tremblay btremblay at me.com
Tue Apr 9 12:32:09 CEST 2024


Until the late 1990s manufacturers seemed to see no value in using standard parts. So many lcd units from these old machines look like a standard 14 pin 1602 display but pins are out of order or the addressing is some weird multi-pin serial scheme nobody remembers. (Five and a half bit at alternating speeds with a strobe, blanking, and reset pin with tri state logic where logical low is minus 7.3 volts.) The tribal knowledge involves hacking modern hardware and usually involves risk.

Benjamin Tremblay

> On Apr 8, 2024, at 9:33 AM, rburnett at richieburnett.co.uk wrote:
> 
> Both of these issues (top line only on the OLED display, and black blocks only on the LCD) sound like initialisation issues with the display controller IC.
> 
> In each case did you have the new display connected at the time when the kit was powered up?  Or only connected the display after power up?  It needs to be connected at boot-up to receive commands and get properly initialised for the right number of rows & columns, etc.
> 
> Failing that it sounds like the replacement displays aren't entirely compatible with the Hitachi 44780 initialisation sequence of the original display.  I've had problems with this before when substituting displays in various bits of kit.  Sometimes the firmware doesn't wait long enough between commands, or it doesn't follow the exact recommended command sequence but still manages to work with some screens (>.<)
> 
> -Richie,
> 
> 
> 
>> On 2024-04-08 13:56, mark verbos via Synth-diy wrote:
>> I added a trim and it only lightened or darkened the black boxes.
>> Mark
>>>> On Apr 8, 2024, at 2:51 PM, Flügel, Werner <werner.fluegel at b-tu.de> wrote:
>>> Am 08.04.2024 um 14:38 schrieb mark verbos via Synth-diy:
>>>> Second, I plugged in the LED backlighted one today. The backlighting looks great, but I only get solid black boxes all the way across the screen.
>>>> Does anyone know about these things? What am I doing wrong here?
>>> Is there a trimmer for contrast? I had a similar effect building the Ambika Polysynth, adjusting the contrast helped in my case.
>>> --
>>> mfG.
>>> W.Flügel
>>> Wir sind IT. Das ist kein Beruf, das ist eine Diagnose.
>>> <7123838.uCcSxbalbl at rotfl.franken.de>
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