Help! Noobie not able to get lcd working

Hello,

This is my first arduino project and I need help. I have the Arduino Mega 2560 and the I2C/TWI LCD2004 Module from dfrobot. I wired it up just like shown in the diagram. When I plugged in my mega via the usb port the lcd lights up, but no characters. I then added the files needed to my library (.h, .cpp,.o), compiled and uploaded the I2C_LCD2004_Sample.pde to my mega and I get the leds flashing on the mega as it is uploading and the lcd still shows nothing, the lcd stays lit up but no characters on the screen. How do I know if I'm doing something wrong or if my LCD screen is defective? Any and all advice would be greatly appreciated.

I have GND connected to GND VCC to 5v SCL to analog In 5 SDA to analog in 4

Thanks, Dan

Disconnect the SCL and SDA, power up the display, do you see any blocks on lines 1 and 3? If not, adjust the potentiometer.

What if you try pins 20 and 21 instead 4 and 5?

http://arduino.cc/en/Main/ArduinoBoardMega2560

Cheers,
Kari

Kari,

YOU ROCK!!! Moved to those pins and the LCD has text.

Thank you for saving a noobie from tons of frustration.

Dan

wardda:
Kari,

YOU ROCK!!! Moved to those pins and the LCD has text.

Thank you for saving a noobie from tons of frustration.

Dan

No problem, I had the same problem year back, and had to find out that myself… really time saver!
:slight_smile:

Cheers,
Kari

I should have used that mega I bought. It is just collecting dust.

liudr: I should have used that mega I bought. It is just collecting dust.

Heh, Mega 1280 was my first Arduino, and least used with all my tests. Maybe it is waiting for the big day, "The Project"-day? XD

Cheers, Kari

Having a similar problem with the i2c display: http://www.ebay.com/itm/190573003243?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

I have it connected to analog 4 and 5, 5v and gnd just like the OP. I am using an Arduino Uno. Anything special I should know before I contact the seller? I tried switching the data lines, adjusted the pot, even tried some different library files. The blue backlight comes on but no text is displayed.

Thanks

Did you try to disconnect SCL and SDA and just power up the LCD with 5V and GND? Can you see blocks on line one?

I was using the wrong library. I downloaded the library per the ebay ad and it didn't work. I tried several others. Finally, I went to DFRobot and downloaded the library on their product page here - http://www.dfrobot.com/index.php?route=product/product&path=53&product_id=135

My board doesn't say DFRobot on the back, it says YwRobot - but this is the only library that works.