Re: Mystery LCD

On 17 Jul 2005 19:37:54 -0700, the renowned spamfilter@xxxxxxxxxxxxxxx
wrote:

>After some more investigation tonight, it looks like Truly is in fact
>the manufacturer; I was never able to get any more information off the
>LCD itself but I did peel back some tape on the ribbon cable and saw
>"Truly" printed on it with some another part number (TG400) that is
>similar to the one on the LCD.
>
>It's definitely 16 pins (I mean it this time!) - two are ground, one is
>perhaps contrast of some sort (it appears to be connected to ground
>through a parallel resistor and capacitor). The remaining 13 pins are
>connected to the Atmel chip as follows:
>
>3 to PortD
>2 to PortG
>8 to PortC
>
>... so if there are three bits for control (say to PortD), 8 bits for
>data (say PortC), that only leaves two remaining unknowns. It's a good
>start, I guess. Too bad I can't get at the program on the Atmel
>chip...
>
>At first glance, the Truly web sites aren't all that helpful, but I'll
>try to dig in a bit deeper tomorrow.
>
>Thanks

Chances are that it's a standard HD44780-type interface if it is a
small character type display module. As others have said, there are
basically 14 pins, but sometimes two more in line that have to do with
backlight optionally (and sometimes the backlight can be brought out
there or to separate pins on some Truly displays). We used a whack of
them about 7 or 8 years ago but had some problems with them.

Anyway, look for info on that interface and you'll find lots of data
for that chip and compatibles. Also code examples that are probably
full of bugs.

It sounds like they are using 8-bit data interface (many applications
use 4-bit mode). It also sounds like they are powering the LCD from a
port pin,if your tracing of the circuit is correct. Perhaps the
contrast pin is being driven by a PWM output with a low-pass filter.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@xxxxxxxxxxxx Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
.

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