I remember older LCD modules that needed negative voltage at Vo pin, but
that was in the 80's and 90's.
For a long time now you just connect the Vo pin to GND via a trim-pot or
a controlled current sink.

Isaac


Em 24/04/2014 11:26, Jacopo Monegato escreveu:
> it *should* work but you need nevative voltage for lcd contrast, which is=
 about vdd-4.5V if i remember right. that's why you can connect that pin to=
 gnd if you power the controller with 5 volts
>
>> Subject: [PIC] Use HD44780A display controller with 3.3 volt PICs?
>> From: larry.bradley@ncf.ca
>> To: piclist@mit.edu
>> Date: Thu, 24 Apr 2014 10:11:08 -0400
>>
>> I have a collection of LCD displays, all of which use the HD44780A
>> controller. I'd like to use these with a PIC24H. From the data sheet, it
>> appears that the  chip should be happy with the 3.3 volt O/P of a
>> PIC24H, since the input pins need a min of 2.2 volts.
>>
>> Has anyone tried this?
>> --=20
>> Larry Bradley =20
>> Orleans (Ottawa) Canada=20
>>
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