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[OT] LCD question

Posted: Wed Feb 13, 2008 3:47 pm
by dman776
This is slightly off-topic, but, wanted to leverage the experience of this group.

We are running a PIC at 3.3V and need to interface to a 5V LCD.
1) has anyone run this WITHOUT level shifting?
2) Do you supplying -2.0V on the LCD ground pin would work?

thanks in advance

Posted: Wed Feb 13, 2008 4:14 pm
by TimB
I would personally not go down this route, but the fact you are.. I would look at the Pic as some have 5v tolerant i/o

What type of LCD do you require?

Posted: Wed Feb 13, 2008 4:24 pm
by dman776
Thanks Tim.
I haven't committed to anything yet as we are in the component ID phase.

I'm interfacing a few peripherals:

PIC (3.3v or 5v)
LCD (5v) -- preferably a serial SPI interface
SD card (3.3v)
vs1003 (3.3v)
RTC (3.3v or 5v)
rs485 (3.3 or 5v)

Posted: Wed Feb 13, 2008 4:54 pm
by TimB
3.3v pic is the obvious choice

If the LCD is spi then might be able to connect the pullups to the 3.3v line or I might be getting confused with i2c :?

Have a look here

http://www.scienceprog.com/interfacing- ... -circuits/

Or look here for 3.3v lcd's

http://www.soselectronic.com/?str=320

Posted: Wed Feb 13, 2008 8:43 pm
by richardb
most 3V to 5V level shifting can simply be done with inline resistors, 1k will do 99% of the time even to quite high speeds. you just need to check the input threshold levels and that the inputs have protection diodes.