Business Card Calculator

Details

This project was partially inspired by the Hackaday business card contest, which I couldn't enter because I work with Hackaday and other Supplyframe entities. But I had this idea long before then -- I love calculators, and if I were going to make a business card PCB for myself, I definitely wanted it to be a small, touch-based calculator that would ideally be thin enough to actually put in a wallet or carry in your backpack/case etc.

So I started to work on this. I chose the ATtiny3216 as it has enough horsepower to do the job but can also just sip current in a low-power mode. I was also strongly considering an MSP430, and depending on how battery life goes, I might switch it in the future. The tiny 1 series chips also have built-in touch hardware, though you are forced to use Atmel's (Microchip's, I suppose) touch library. They don't give you any details on setting it up yourself. I wanted it to be pretty much all surface mount, as I find surface mount soldering easier than through hole for a lot of projects. I borrowed an idea I had seen in other projects of putting the coin cell battery in a circular cutout to prevent it from making the board too thick. If I can remember the project where I first saw this I'll credit it here, as it's a great approach.

I wanted to use an OLED display, both for the low power draw and also the very high contrast. I've worked with the SSD1306-based OLED displays before, and even written my own C library for interfacing with them, so that seemed like a good choice. I've never actually mounted an OLED on the opposite side of the board from the flat flex connector, so I carefully measured the distances based on the datasheet drawings for the displays I ordered. I was worried the thin cutout so close to the edge of the board might be difficult for the PCB house, but they had no trouble at all it seems.

Progress

This is the repository for the hardware. I haven't actually finished the software yet, though it's a work in progress. I have a batch of prototype PCBs from DirtyPCBs (the best board house around) and will order the BOM and solder one up to develop with. The version of the PCB in this repository has generic text on the back (I actually have the calculator side as the "front" and the business card info side as the "back" though it's really sort of arbitrary) so you'll need to replace the text with your details if you want to use this design.

License

The hardware is licensed under CERN-OHL-W and therefore you can freely use the design as long as you follow the license. The software, once released, will be under the MPLv2 most likely. See the license file for details.

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