No i2c address found for 20x4 display

Other Hardware Displays
1

Hello all, I am trying to get a 20x4 display working that I purchased from here. It uses an i2c interface, so the first order of business was to find the correct i2c address. I used the sketch found here.

I made the following connections:
(UNO -> Display)
5V -> VCC
GND -> GND
A4 -> SDA
A5 -> SCL

The scanner sketch was unable to find any i2c addresses. I'm pretty sure I have everything set up properly, have checked the wiring about 100 times and tried several different versions of the i2c scanner sketch.

Any ideas what I could try to get this screen to interface?

2

3 common mistakes when starting with I2C

  • swapping SDA and SCL lines
  • using digital pins 4 and 5 when you should use analog pins 4 and 5
  • no pull up resistors

All you ever want to know about I2C can be found here - Gammon Forum : Electronics : Microprocessors : I2C - Two-Wire Peripheral Interface - for Arduino -

3

You have provided a link to a page that shows a picture of the LCD itself whereas your problem lies in communicating with the adapter board attached to the back of the display. A photograph or a really good description of that adapter including the part number of it's IC chip will help us a lot.

A nice tutorial that may help can be found here: --> http://arduino-info.wikispaces.com/LCD-Blue-I2C

Don

4

floresta:
A photograph or a really good description of that adapter including the part number of it's IC chip will help us a lot.

Eh? Looks like a bog standard PCF8574 one to me! (Mind you, I don't recall having one with a pilot light.)

If it is I2C and you connect it right, the "scanner" should find it. Then you use the other program to find its descriptor.

Sainsmart website unfortunately offline at this moment!

5

I seem to have missed those other pictures!

It looks very similar to the first one in Terry's tutorial.

Don

6

floresta:
I seem to have missed those other pictures!

You have to permit all sorts of spurious "helpers" in NoScript. In this case, I think it was that nuisance "cloudflare".

floresta:
It looks very similar to the first one in Terry's tutorial.

Except for the colour of the LED and the "Sainsmart" writing.

As you are prone to observe, you can't trust anything with these multiply "cloned" boards. :grinning:

7

You have to permit all sorts of spurious "helpers" in NoScript. In this case, I think it was that nuisance "cloudflare".

I know that I have to do that in order to actually look at the pictures but in this case I totally overlooked the fact that they were there.

I think that the perpetrators of these cloned boards arbitrarily mix in some 'A' suffix ICs to make it harder to get them operating.

Don