RPN-duino

[Chasfield]

The Due calculator has progressed. It is a bit of a brick since it is built around a Due board with header sockets and runs off a PP3 battery. A much lower profile device would have resulted from using a solderable Due PCB combined with a LiPo battery plus charge controller - that will be a project for the future.

Otherwise things have gone well. Compared to the regular Arduino, this thing goes like a rocket. It computes 170 factorial in the same subjective time that it takes to add 2 + 2 and the I2C connected display responds with no perceptible lag. The relatively huge RAM space allows for the reckless use of a variety of u8glib display driver fonts. With my previous designs, I had abandoned this convenient graphic device library and resorted to writing my own display driver code to avoid running out of RAM variable space.

Attached is a picture of the calculator in its alternate high precision one line display mode showing the answer to 170 factorial.

The only fly in the ointment is the documented hardware bug on the Arduino Due R3. From a cold start it runs the boot loader instead of your code and sits there doing nothing. A subsequent power cycle or hard reset is necessary to get your code running. There are hardware and firmware fixes for this, but right now I don't want to blow my board up. The problem was fixed on newer releases of the board.