Interested in feedback for ideas of a calculator design

[knapik]

I would like to create a calculator that is very much inspired by the EE favourite Casio fx-61f. They're quite hard to come by and are a pretty unique design, so I thought that some people may be interested in a somewhat homage. I haven't gotten too far into my design, as I've been busy with university, but I wanted to ask for feedback from others to see what they may be interested in. I should note that this will mostly be an open source hobby project, but I wouldn't mind to try and make some to sell if people are truly interested.

• I've had troubled deciding on a display. I would like something ~3" in size and graphical. I initially wanted to use an e-ink display, but I worry that it may be unsuitable for a calculator. However I can't decide whether to go with a regular TFT display and include a rechargeable battery and supporting circuitry due to high display power consumption, or use something like a Sharp memory display to save power, but pay extra for the display itself. What would others be interested in having for a calculator?
• I believe that an RPN and PN mode are essential, but I don't have any loyalty towards an algebraic mode. Would anyone consider this to be a deal breaker?
• Arbitrary precision floating point calculations would also be nice, but I worry that may be a not have much of a real world use.
• I want to use a Scheme interpreter as the programming language for the calculator and have user defined  functions stored in a file on the calculator.

I would love to hear if anyone else has any suggestions, opinions or just general interest in the project.

[Wimberleytech]

Interesting project...I am sure you will learn a lot.

There are more than enough calculators on the market (both hardware and ap-based) that your market penetration will be approximately zero.

RPN vs Algebraic...two religions that will ultimately resolve at Armageddon.  My bet is on RPN.

What is PN???

Display is uber critical.  I have an HP42s.  I love the calculator, but hate the display.  So, I use my HP32S.

[Berni]

I found myself using calculators less and less ever since getting out of university.

A good graphical calculator is a lifesaver on a uni exam where this is the most help you are allowed to have, but in a electronics design day job you are allowed to use anything that gets the job done, and most of the math you come across is pretty simple anyway.

Since i do most of my work in front of a PC i got really used to using SpeedCrunch: https://speedcrunch.org/
For someone used to algebraic it works really well by just typing the expression in. The part i like the most is that it calculates the result as you type, this gives you some of the RPN benefit of seeing the intermediate steps to your result. User interface is also no bullshit, no buttons or anything since im using a keyboard anyway so all the space is left for showing history. To me this is an experience beyond what a typical handheld calculator provides.

Calculating on the go is the only place i still see real calculators still having the edge. Running a calculator app on a phone just doesn't really provide as good of a experience trough the touchscreen. But then again a extra android app takes up zero space in your pocket while a calculator is as big as the phone itself (And lets be honest who goes anywhere without a cell phone these days).