Problems with Arduino DIY Doser

[Gastel]

Hi guys,
I am currently having a go at programming/building a dosing pump using arduino for my RSM 130D.
I had it all wired up and running fine then suddenly my I2C lcd display started showing only blank white squares along the top line.
I have since gone back to basics and tried just running the old "Hello World" scketch but for the life of me I can't get the LCD to display anything.
I have swapped arduino board, I have two uno's and a mega 256 and I have swapped LCD's from a 16x2 to a 20x4 but I cant get anything to display.
I am pulling my hair out and am so frustrated that I am ready to ditch the whole thing, especially seeing I had it working and ready to mount.
Can anyone out there help me PLEASE. :angryfire: :angryfire:

 

[sleepydoc]

You might try the Arduino forum - more people with knowledge on Arduino there.

Just to recap - working fine, then LCD stopped working. Went back to the basic "hello world" script and still doesn't work. Tried different Arduino boards and different LCD with the same results. Correct?

Is it the same or different i2c chip on the LCDs? Could that be fried? Have you tried hooking up the LCD without the i2c? Most (but not all) of the smaller LCDs use a standard Hitachi 44780 interface that you can hook directly to the arduino, it just takes more wires.

Is it possible one of your libraries got corrupted? Do you have any other i2c devices that you can try to make sure the i2c pins on the arduino aren't fried? (shouldn't be the case if you've swapped boards, but good to check)

You can also run the i2c scanner to make sure the i2c device is being recognized.