interfacing 5V LCD module with a 3.3V micro

[is_razi]

hi there,
can somebody help me interfcaing 3.3v uc(like ATXmega) to a 5V LCD without using voltage translator.is there anybody who have done this before.is it possible to operate the LCD module with a 3.3v logic supply and 3.3v logic inputs .
if you have any experiences about this case please let me to know about it.
thanks in advance.

 

[Kurenai_ryu]

well it depends which LCD.. you must check the datasheets, I once made it work an LM12864L directly BUT you SHOULD NOT READ data back from the LCD, to make a command efective or data output, just wait... DONT READ STATUS OF LCD!!!! of course a 3v3 buffer will help youif you even commit this error... again check the minum HIGH level on datasheets, (sometimes is 3v sometimes is 3.5v when it's 4v it'll not work...)

also you can make a level translator easily with some transistors, espacially if you are not going to read back data from the LCD...

how about writing and reading from the LCD? only a level translator could help... again check the web there is a bidirectional level translator with a single MOSFET by bit... it's not so hard to implement...

 

[is_razi]

hi dear Kurenai_ryu
what if i use 3.3 zeners on micro side for data read.i think this will solve the data read problem .
can you tell me please if i supply the LCD module using 3.3v it will work or not.have you done this before.sorry i am designing the pcb board and i want to be sure about everything .
thanks.

 

[wp100]

Hi,

Well if you can match 3 v to 5 v devices there would not be any need for translator chips..?

First check your micro, does it have any input pins that are 5v tolerant - some micros do have them - that would sort out your read problem.

Writing to your lcd, it is impossible to say as you do not give any details of the lcd you are using.
If it is a 5v lcd they generally will only run at 5v, in my limited experience, so you really need some form of active voltage translator to get the 3v3 up to 5v level.

The other alternative is to use a micro and lcd of the same voltage, which might be a simpler way in the long run as more and more lcds are being made at 3v3.


https://www.microchip.com/stellent/groups/techpub_sg/documents/devicedoc/en026368.pdf

 

[M!k]

Most probably you'll need level converters for the interfacing.
This guy did exactly what you need using simple FETs:
https://delphys.net/d.holmes/hardware/levelshift.html

 

[cool.man]

Check datasheet of LCD what it says.
If the data pins of LCD consider a logic level high at 3.3v then connect the data pins directly to microcontroller.As far as power supply of LCD is concerned what you do is simply use a 5v regulator and power LCD using this 5v.

I have done in a same manner and it is working fine.

 

[mjbcswitzerland]

Hi

A lot of 3V3 processors have 5V tolerant ports and can be used connected directly.

Most 5V LCDs will also operate at 3V3 (they become slightly slower - this is noted in their timing spec). Usually they need a slightly negative contrast voltage when powered by 3V3, which can be a bit of a nuisance though...

Regards

Mark

www.uTasker.com