[OT] LCD question

Coding and general discussion relating to user created compiler modules

Moderators: David Barker, Jerry Messina

Post Reply
dman776
Posts: 115
Joined: Mon May 28, 2007 3:59 pm
Location: Texas

[OT] LCD question

Post by dman776 » Wed Feb 13, 2008 3:47 pm

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

TimB
Posts: 262
Joined: Wed Oct 04, 2006 7:25 am
Location: London UK

Post by TimB » Wed Feb 13, 2008 4:14 pm

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?

dman776
Posts: 115
Joined: Mon May 28, 2007 3:59 pm
Location: Texas

Post by dman776 » Wed Feb 13, 2008 4:24 pm

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)

TimB
Posts: 262
Joined: Wed Oct 04, 2006 7:25 am
Location: London UK

Post by TimB » Wed Feb 13, 2008 4:54 pm

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

richardb
Posts: 265
Joined: Tue Oct 03, 2006 8:54 pm

Post by richardb » Wed Feb 13, 2008 8:43 pm

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.
Hmmm..

Post Reply