RPN Scientific Firmware for the Spikenzielabs Calculator Kit

[Maximilian Hohmann]

Hello!

Wonderful projects your micrcontroller/Arduino based calculators! I am also tinkering with these things and have been putting together parts for a calculator for quite some time. Right now, I am waiting for a shipment from China with buttons and transparent keycaps for self-labeling. When it's there I will start soldering...

Regarding your projects I have a couple of questions and a suggestion:

- Does the housing of the Spikenzie calculator offer enough space for mounting the microcontroller in a socket? I ask because I have already "fried" a couple of them, mostly because loose wires on the breadboard got in contact with the wrong pin. And in-site-programming always comes with a certain risk of connecting the wires in the wrong order... De-soldering the controller from that calculator PCB would be beyond my capabilities.

- On one of the pictures I can see a MacBook pro, similar to what I am using. What ISP programmer and which software are you using to flash the controller in-site? And what settings do you use for bringing down the power consumption that low?

- As I am a big fan of LED displays I would never build a calculator with anything else (except maybe nixies or other glow-in-the-dark steampunk stuff). After some research I found these displays most useful: eBay item number 121031909296 . Different to every other display I have seen so far, their PCB is exactly the size of the display itself, allowing them to be combined horizontally (for multi-digit displays) and vertically (for full-stack or other multi-line displays) without gaps. They have MAX7219 controllers, therefore only three wires are required to connect any number of them. Unfortunately they are sold as kit only with three SMD components that can be a bit difficult to handle.

Looking forward to see more of it coming!

Regards
Max