Hi Markus, thank you for the prompt reply.
What about the possibility of the tester work at 3.3V?
Is it possible without reduced functionality?
I've been looking into the code and the most difficult part of adapting a different sized display is the fact that it was written mainly to the 16x2 or 16x4 format.
With the display I have mentioned (based on the PCD8544), it's very easy to get 14x6 characters.
Of course it will take some extra program space, but with atmega 328, I don't think it will be a problem.
What if we create some middle level functions that will be between the main program code and the low level display functions.
Depending of the display type defined in the makefile, this set of functions will adapt the output accordingly.
As long as the display need only 6 data pins, the hardware could continue to be the same.
You only have to choose which type of display at compile time, all the rest should be automatic.
What do you think about it?