Monthly Archives: November 2014

LCD – Common Anode or Common Cathode?

It has come to my attention recently that there are some LCD display modules on sale that are ‘Common Cathode’ types (e.g. this one from SparkFun) , rather than the more common ‘Common Anode’ type (e.g. this one from Adafruit).

Why would you care about this?

Because the two types of display essentially operate with ‘inverted’ logic signals relative to each other, you will probably find that your LCD display is very dark after you upload the ‘wrong’ Automation code. Essentially the ‘common cathode’ type is insisting that white is black and black is white – just like some people we know!

If you’re got an RGB display then all the other colours will not appear as intended either and they won’t match what’s stated in the User Guide.

As a result I’m now providing two versions of the Automation code on the Updates page so make sure you use the correct one for your LCD type.

If, after uploading, your screen is very dark then try the other version.

A handy feature I’ve added to the code (thanks to Eric Thacker for prompting me to implement it), the unit now ‘remembers’ the last preset or user patch that you used and starts up with this when it’s next switched on, rather than always defaulting to Preset 0: Apache. This is actually very convenient if there is a favourite patch you use a lot 🙂

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