Display Troublehooting

Hi all,

Looking to get my first Arduino project up and going with a sample sketch to test the screen. I cant seem to even get it to power it up.

The display I'm using looks different to the others in the tutorials as its all integrated with the I2C driver, I've connected the clock, data, VCC and ground but no backlight and I2C scanner doesnt find anyting.

Before I contact the seller to return the faulty screen, can anyone see anything obvious I've done wrong? I've confirmed there is 5V on the VCC pin at the display.


You get a much better chance to get a sensible response, if you provide a link to the seller of this display.

Google was not of great help searching for this special LCD.

The inking on the pins look more like SPI than I2C, e.g. SCK and CS.

You may need to connect additional pins for backlight.

Make sure the solder points are really connected by the PCB, and not only to there to hold an add-on board.


It seems to have an ST7070 controller with SPI interface.

Here is a module from BuyDisplay

They have some 8051 example code. I suspect that someone, somewhere has written an Arduino library. The commands look just like most other 16x2. If you don't find a specific ST7070 library, modify an ST7920 (SPI) library (in character mode)

So it certainly is not I2C. But it looks a nice display.


Thanks for the response. That makes a lot of sense!

Should the display still power up with 5v on VCC? There is continuity between VCC on the serial header and VCC on the parallel header, can’t see any other pads that might be used for power.

V0 is listed as contrast, no change when 5v is applied to that pin either

You should have got an answer to your last post by now, by someone more competent for LCDs than me.

V0 is for contrast of the liquid cristal part of the display, and should get a voltage between GND and VCC, usually by a potentiometer; there are many posts about this.

You can barely see the LDC without backlight. LEDA and LEDK are for this. Should be covered in the tutorial.
Make sure there is a series resistor to limit the current, e.g. by initially connecting LEDK LEDA through ~220ohm to VCC, LEDK to GND, and measuring the resulting voltage on LEDA.


edit: finally fixed the typing error.

You connect the Backlight LEDA, LEDK via a small resistor. Some modules have a resistor on the pcb. It is safer to try with an external resistor. Select for the desired brightness.

It looks very simple to use the SPI interface.
But since it also has a standard parallel interface, you can probably drop it straight into an existing 16x2 socket.

Have you read the documents from BuyDisplay?


Agree with David. Connect the backlight LEDA with a small resistor.

thanks for the help guys, i misinterpreted the docs. After hooking up LEDA/K i get the backlight up :slight_smile: