Any 4x20 or 2x20 SERIAL lcd running on 3.3v?

Hello, Im trying yo design a project running on a WEMOS D1 R2 board (3.3V) which needs a text LCD
It could be either a 4x20 or a 2x20 LCD, but I can't use those tiny 0'96" ones

As the Wemos boards don't have too many Digital pins, I would need to use serial interfacing with the LCD (either SPI or I2C). I don't have enough available pins to drive the standard parallel LCD buses

Then I found those 4x20 LCD's that use a "backpack" (PCFxxxx) board that turns parallel into I2C, which look good but they all seem to work only at 5V, and all these Wemos boards run on 3.3v logic

Anone has dealt with this before??

Thank you!

I just realized I do have a 5v out from the Wemos Board, I guess I can use it to power my PCFxxx converter, will that be ok with SPI levels?

Thanks

Read the data sheets for the Wemos Board and find out how much current that output can provide. In general no Arduino 5 volt output would do. I will most likely not manage the back light of an LCD.

My understanding is that provided that you are powering the Wemos Board thru USB, the 5V pin would be getting direct current from the USB voltage, am I wrong?

Actually I just checked and between USBVCC and +5V there's only a 2A fet that drives it when Vin is LOW, so I should be good.

Thanks!

What is a pure Wemos and a Wemos Board? Assuming that the Wemos Board works like f ex. an UNO it sounds like okey. The limiting factor would then be the USB pwr supply.

edugimeno:
Actually I just checked and between USBVCC and +5V there's only a 2A fet that drives it when Vin is LOW, so I should be good.

Thanks!

As long as You pull out less than those 2 Amps, yes, You must be good.

You ought to be good regarding the +5 volt but You'll need level shifters for the I2C to handle the 5 volt LCD.

Railroader:
You ought to be good regarding the +5 volt but You'll need level shifters for the I2C to handle the 5 volt LCD.

That's what I expected (level shifters) to use but I've found lots of schematics now using direct connection between LCD's (powered at 5V) and Wemos boards, then I found that it's stated everywhere that by ESpressif, all ESP chips' digital inputs are 5V (some say 6v) tolerant

If this (among many other) works, mine should, too :slight_smile:

Read the data specs for the Wemos! That's the only thing You can trust. There are Arduino projs pulled by amateurs that happily run 5 volt into 3.3 volt devices, claĆ­ming it doesn't work using suitable levels. Bullshit. A properly made construction survives for ever, amateur experiments will not.