At 09:31 PM 9/3/2003 +0300, you wrote:
>Thanks to all who responded. Maybe I did not make myself clear. I have
>hd44780 compatible lcds which are no-name no-datasheet types ;-). They
>work ok but there is not enough contrast even if the Vee is taken to GND,
>with nominal 5V supply. These LCDs do not allow Vee to go negative.

How do you know this if there are no data sheets?

Standard temperature LCD glass requires the controller 5V < Vee <= 0V.
Extended temperature types do require more like 0 >= Vee >= -5V.

I suggest adding a 7660 and a couple of capacitors..

Best regards,

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

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