RPN-duino

[Chasfield]

After tidying up the built-from-parts joystick calculator, I decided to produce something similar but with a much higher specification. I have stretched the low cost Arduino Nano to its limit, with my code bumping against both RAM and flash memory ceilings. However, The Arm based Arduino Due is much more powerful and packs 96 KB RAM and 512 KB flash storage. It also has about a zillion I/O pins. The big deal with this device is that it supports true double precision floating point maths.

For the physical hardware I have gone for a 1.3 inch OLED - these can be had for what a 0.96 inch unit used to cost. I have conjoined two Farnell 4x4 keypads to give 32 keys. Some minor "chopping" was necessary to reduce their footprint. The makers have upped the spec. of these as the key tops are now of double-shot construction, which is not so useful to me. For example, on the last calculator I was able to scrape away at the letter "B" to leave a pretty decent decimal point! Also the back of the keypad is now heat staked rather than screwed on, which made moving the key tops around from phone to calculator layout a bit more difficult.

I have attached a picture of the Due based calculator in a fairly raw state, sans keyboard labels.

It is displaying the result for the tan(355/226) trig torture test. This makes me happy.