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[on:]

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

[Reply #1 on:]

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

[Reply #2 on:]

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

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

Cheers,
Kari

[Reply #3 on:]

Kari,

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

Thank you for saving a noobie from tons of frustration.

Dan

[Reply #4 on:]

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!
 

Cheers,
Kari

[Reply #5 on:]

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

[Reply #6 on:]

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?
 

Cheers,
Kari

[Reply #7 on:]

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

[Reply #8 on:]

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?

[Reply #9 on:]

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.