[lcd4linux] Re: Everbouquet 44780 modules

[Aragon G. <ar...@ph...>]

| By Michael Reinelt <re...@eu...>
|                                          [ 2004-02-16 10:10 +0200 ]
> try to post such questions to the list!

Okay ;)


> >The reason I'm asking is because I have one, and I can't help but notice
> >some of the unused circuitry on it.  There are pads for a transistor and a
> >bunch of resistors which looks unmistakebly like a switching circuit
> >attached to the LED backlight Anode.  The base of the transistor pads leads
> >through a resistor pad into one of the controller chips.
> >
> >I'm thinking that perhaps these modules have an undocumented 44780 command
> >to toggle the backlight on and off, maybe even to adjust its intensity 
> >too. I've tried mailing them asking this, but so far no luck with useful 
> >replies. 
> 
> Can you tell what controller pin is connected to this transistor? I 
> could search through my various datasheets to find an answer...

I'll try take a photo of it tonight.

I can trace the track going into one of the silicon chips embedded on the
controller board, but that's it.  It also jumps through to the otherside of
the board, but can't trace it there (without breaking my module).

Before I went to bed last night I checked the voltage between the base pad
and ground - ~2.7V before 44780 initialisation, ~2.5V after initialisation.

I'm going to hack up someone's source code tonight hopefully and see what
happens if I play with the two "unused" bits (D1 and D0) of the Set
Interface Length and Move Cursor commands. ;)


Regards,
Aragon