Monday, August 26, 2013

Raspberry Pi and the Nokia 5110 LCD: contrast value is important

There comes a time in every tinkerer’s life that you think of a project for which a small display device would be a nice addition. Think of displaying a temperature, the time, status ‘on’ or ‘off’, etc.

It is of course easy to go to Adafruit or Maplin’s and order an LCD and for roughly $20 you would get something useful. Plus shipping naturellement.

I happened to stumble on the blog of scruss and his Quite Rubbish Clock. He uses a Nokia 5110 LCD, a 1.6” device. I believe these are surplus from old Nokia 5110 phones from around the year 2000. I had me one of those phones, nothing fancy but very reliable. The first text message I ever received was on it!

Anyway, I searched around on (Deal Extreme) and ordered 3 of these displays for the grand price of $16.20. Wait a few weeks for them to arrive and voila: time to play.

I followed the installation instructions contained in scruss’ blog. I won’t repeat them here.

However, when I ran my first test, the back light came on but then: nothing. After checking and rechecking my wiring, re-installing the software and still nothing, I decided to browse the Raspberry Pi forums to see if anyone had any advice. After a few fruitless hours, I found that the right contrast value of the display is crucial to its ability to display something.

User ‘bgreat’ on the Raspberry Pi forum had written a Python class to make using this device possible ( User ‘pest’ on the same forum had enhanced this class even further to the point where, if the class is run as ‘main’, it goes through a number of self tests, which I think test every possible scenario. So I downloaded that version and am using it for my next project. Which, by the way, is almost ready for public showing…

1 comment:

Zoth-Ommog said...

Thank you so much - your post saved me from a lot of frustration.