I am planning to build a calculator using Arduino as the base. I already know C and I love low-level stuff, so I guess the software part won't be a problem.

However, I've been stuck with Arduino. What I need is something capable of doing math (as I'm not even sure if Arduino has a FPU), and it to have enough inputs for more than the basic 0-9 + - / * keys.

I am a real newbie when it comes to hardware. I don't even have the slightest clue where to start. I barely understand Arduino's specifications, which is why I'm asking here.

I want to do something more than the classic calculator, because the software part is not a problem. I just need help on which hardware should I choose; both on the 'which Arduino' and 'which accesories for the Arduino' parts.

P.S. I have some experience with x86 assembly; does that mean that 86duino or Intel Galileo are better for me?

3 Answers 3


Start with the biggest (AVR) Arduino you can afford, and worry about miniaturizing it once you have the basics in place. You may find that you don't actually want an Arduino in the end, but something like the ATmega169PA instead so that you have native LCD support (instead of having to use a discrete LCD module).

P.S. I have some experience with x86 assembly; does that mean that 86duino or Intel Galileo are better for me?

Doesn't matter. Most of your x86 assembly experience will easily transfer to AVR (but not all, since the AVR core is simpler than x86).


For the most part, none of the AVR based arduinos are any better at number crunching than any others. They all have a single AVR core running at 16Mhz. None have an FPU, but the software floating point code is very efficient and at the time scales you care about for a calculator, it really doesn't make much of a difference.

The biggest differences between models are memory and available IO, so the decision between AVR models should probably come from what kind of peripherals you want to plug in, not what you want to calculate.

That said, if you want to do a lot of high precision, numerical calculations (like numerical integration or something), you will probably want something with more memory, and floating point types larger than 32-bits. I don't have much experience with those models, but I'm pretty sure that a Yun or a Zero would be better suited for those kinds of calculations. They don't use AVR based main CPUs.

For IO there are too many options to enumerate here. Take a look at the usual suspect's pages (sparkfun, adafruit, etc...) for displays and buttons. These sites have good descriptions and example code for everything.

When picking devices, remember that you can have multiple I2C devices plugged in at once, but only one UART serial per port (uno/leonardo 1 port, mega 4). Software serial can give you more UARTs for low speed comms if need be.

If you want a lot of different individual buttons, there are ways to get more than 1 button per pin, but it would be a bit easier electrically to pick an arduino with as many pins as buttons. Some of the keypads available already have a special wiring scheme to get higher than 1-to-1 pin ratios and descriptions of how to use them, so they might be a good pick to get yourself started.

  • Correction: The Yun does have an AVR MCU.
    – DaveP
    Feb 21, 2015 at 20:47
  • 1
    It has a 32u4 for IO, but the atheros MIPS chip @400 MHz would be used for the calculations.
    – BrettAM
    Feb 21, 2015 at 20:53

Any Arduino (I would start with the UNO) will be sufficient to make a calculator similar to the regular HP or TI calculator product line.

For the keypad, you will need to buy an I2C compatible keypad and connect it to the I2C lines. For the screen there is an LCD shield.

You will not need to code anything in assembly. You can write cpp code using the libraries provided with the Arduino.

  • Much more like a matrix keyboard than an i2c one. Feb 22, 2015 at 15:37

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