Wow! I read through the posts on Tracy’s project, and this is all kind of blowing my mind. I’ve gotta go get one of these Makey Makey kits.
It sounds like you want braille entry and not necessarily braille output or labels. Is that correct?
I haven’t worked with Scratch before (feeling kind of inspired now, so that will probably change), so I don’t know how difficult this would be to program, but you might consider using 6-key entry. I recently made this video demonstrating 6-key entry for another project I’ve been working on. The video shows 6-key entry on a Perkins brailler, and then I demonstrate what six key entry looks like in braille translation programs (in this case, Braille Blaster). The end of the video shows how the software won’t enter a character until I release all of the keys.
With 6-key entry, which all braille users will likely be familiar with, you strike multiple keys at once to form the different characters. If you could code this properly for the calculator, you’d probably need 7 keys (6 for braille and one for space or enter), and users could create any character they needed.
The braille math code may vary depending on where you’re located. Most English speaking countries are using the Unified English Braille (UEB) code for math content. In the USA, we switched to UEB a few years ago for everything but math, and we’re clinging to our precious Nemeth code for math and science content. For this calculator project, there are some important difference between the two codes. Nemeth numbers are formed differently. Operators are typically a single character in Nemeth, but they’re two characters in UEB.
I hope this is useful information. I’d be happy to answer any follow up questions.