Connecting an Arduino Mini-pro to a LCD display


I'm trying to connect an Arduino Mini-pro (5v version) to this LCD display....

I've had no trouble connecting this LCD to a Uno or a Mega in previous projects, so I though it should be just as easy for a Mini-pro.

I've been working from the example shown here....

The only change I've made from the uno/mega versions are the pin numbers, these are the pins I've used.... LCD RS pin to digital pin 4 LCD Enable pin to digital pin 5 LCD D4 pin to digital pin 6 LCD D5 pin to digital pin 7 LCD D6 pin to digital pin 8 LCD D7 pin to digital pin 9 LCD R/W pin to ground.

so I intialise the LCD with the command LiquidCrystal lcd(4, 5, 6, 7, 8, 9);

My sketch is based on the tutorial above, but has been changed to display a slowly incrementing number rather than just 'hello world'

The sketch will successfully display the number to the serial monitor, but not to the LCD. I guess this proves the mini-pro is working ok. The sketch will also work fine with the Uno/mega versions. I've continuity tested my (homemade) shield so I'm reasonably confident that the screen is wired as intended. The LCD itself is mounted on header pins, so I can remove it an put it in another shield where it works just fine.

Any suggestions for further test/changes I can make? My current best-guess is that either the pro mini is simply not compatible with the LCD screen, or some of the individual pins I've used aren't suitable.

Suggestions appreciated!

What about the LCD contrast? Do you have anything connected there as without it the display will probably not show up though its working.

Panic over! - It was a nearly microscopic short on the shield.

Bugger - should have spent more time testing the board and less time writing the post!


Glad you got the problem sorted. Shorts and open circuits are a PITA for home builders.

If I had a nickel for every time I've troubleshot a hardware problem by looking in the software...