Using a 16x2 LCD with an I2C module

Other Hardware Displays
1

Hi everyone,

I'm currently working on my first project (an irrigation system) and since I'm running out of pins on my Uno R3, I got an I2C module for my LCD. It uses a PCF8574T chip (datasheet) and I just can't figure out how to use it.

First I soldered a female header strip to the 16 holes of the module and plugged my LCD in there. Both the I2C module and the LCD module were marked with "1" and "16" on both ends of the contacts and I made sure that these numbers were matching. I connected VCC and GND to +5V and ground and SCL/SDA to the respective pins on my Uno. I used 10K pull-up resistors for the SDA/SCL pins.

I found an alternative LiquidCrystal library that also supports I2C and there was a "hello world" example for I2C that I tried to get running. I changed the lcd address in the example and the only one that worked at all was "0x20". But it doesn't show "hello world", it only shows random blinking cursors in different places.

Can anyone help me out? I think I've come pretty far all by myself but now I'm a bit lost. I don't have a programming or electronics background, so many things aren't as self-explaining to me as they may be for some of you guys.

Thanks a lot in advance! Please let me know if I left out any important info.

2

i2C need pull up resistors, did you use them?

a pull up resistor takes care that the signal becomes nicely square.

a very informative site about I2C - Gammon Forum : Electronics : Microprocessors : I2C - Two-Wire Peripheral Interface - for Arduino -

3

Check out the information here: --> http://arduino-info.wikispaces.com/LCD-Blue-I2C

Don

4

robtillaart:
i2C need pull up resistors, did you use them?

Yes, I did. I used 10k resistors but since it didn't work, I also tried 5.6k. They didn't work either.

5

I found a working "hello world" example:

I adapted it to my sketch and the display is working now. So many free pins!

Thanks a lot for your answers!

6

Typical instructable.

I hope you put your adapter board where it belongs, behind the LCD module.

Don