RPN-duino

[Chasfield]

I have been working with a 1.3 inch 128x64 OLED display - just right for displaying a 4 line RPN stack. This size is one up on the ubiquitous 0.96 inch units that are available and costs about twice as much (15 GBP). They have great readability and, being self-luminous, rather than back-lit, exhibit near perfect contrast. The I2C ones, with a 4 line connection, only use two data pins on the Arduino, which simplifies soldering.

My most recent Arduino calculator project uses one of these displays and a high quality slim project case (see attached pictures). The keyboard was scratch-built using a matrix of 12 mm tactile PCB switches, much epoxy resin and some tinned copper strip for the row bus lines. The column bus was formed by bending and daisy chaining the PCB switch legs. The calculator runs happily on 3 AAAs and the OLED unit is powered off the Arduino's 3.3 volt pin. It doesn't seem phased by 4.5 volt logic signals. If it dies young I will retract this observation.

The calculator code is the same as my earlier projects but tweaked to push out all four stack lines using U8glib library calls.

See if you can work out which household artefact I cut my display bezel sections from!