After indulging myself with trying out different hardware and prototypes, I realized that I really don't have enough information to design a good badge. You know, all those displays and chips and sensors and buttons and batteries are cool, but at the end of the day you have to *design* something that serves a *purpose*, and if you don't make that the center of your design, there is a big chance it will suck. So let's take a step back and think what we need.

Core Functionalities

Things without which a badge is not a badge. These are non-negotiable requirements.

Identification

This is so basic, that it's easy to forget about it, and go designing watches or belt buckles. First and foremost a conference badge has to identify its wearer to all other conference participants that they might meet. That usually means that it has to have the owner's name (or nickname) displayed prominently somewhere at all times in a way that makes it visible and easy to read from a relatively large distance.

In practice, this means that the badge has to be worn in a visible place (traditionally on your neck, but clipped to your breast pocket or bag strap would also work). It also sets the minimum size of the badge — it can't be the 5×5cm tiny little device that I initially planned — that will simply not work.

The simplest, most fault-proof, long-lasting, convenient and obvious way of achieving this is to simply have a white area on the badge where you can write your name with a sharpie. It always works, even if you run out of battery or release the blue smoke, you can fix it if you made a mistake, and you don't need to know the names of all participants up front — you can even have some spare badges. It also makes it obvious which badge is yours, in case you mix them up while hacking on them.

I really have no idea what I was thinking with the e-ink display.

Contact

The second function of a badge like this is to provide your contact information to anyone you choose. Whether it's a vendor at a booth asking to scan your badge, another participant that you have just chatted with and want to continue it online, or a group of people that you want to go to lunch with next day — the idea is pretty much the same.

The simplest, "analog" way of solving this is of course to have your e-mail address (or twitter handle, or whatever) written then on your badge, in letters small enough to not be visible from afar, so that the people wanting to copy it (or take a photo) have to come close and possibly ask you. But there is a lot of room for technology here.

Bar and QR codes, NFC tags, IR beaming, BLE and other wireless communication methods can be helpful here. Being compatible with existing devices, such as phones, is a big plus here, of course, but we shouldn't require people to have a phone to use it. Ideally, there would be several methods available, with the analog fallback in case of a dead battery.

Extras

Those are the thing that make the electronic badge more useful than the piece of paper that you normally get. They should be good enough to justify the extra expense and hassle.

Self-expression

This is a Python-based badge for Python conferences, so it's fundamental that you should be able to (easily) program it with Python. That's the whole point of using MicroPython/CircuitPython here. But it's not enough to just be able to run your program on it — you should be able to show off the programs you have written!

That means that the badge must be able to run the program while you are wearing it (and not just when connected to your computer), which implies a battery. It also means that the results of running that program should be visible and unique.

RGB LEDs are nice for that, because they are flashy, colorful, and visible from far away, especially when blinking or cycling colors. Unfortunately, a lot of LEDs can run down your battery pretty fast, and also there is only so many ways you can make them blink — so the uniqueness aspect suffers a bit.

A LED matrix provides much more freedom of expression. Even if it's monochromatic, you can display images, scroll text, play animations, visualize data, etc. — the possibilities are very rich and can be very unique.

A display can be even better, even though cheap displays are rather small, so it wouldn't be so visible from afar.

Sound could also be used for self-expression, but it can get very messy when a lot of people do it all at once. There would also have to be a fool-proof way of muting it (preferably a physical switch) for the talks.

Entertainment

It would be nice if it was possible to play games on the badge — either provided, or — even better — written by the participants themselves. This can be great for the boring talks or waiting in queue for lunch, but it could be even better to have multi-player games, or other kinds of games requiring interactions between the participants.

Of course, for this you need some kind of a display (or the LED matrix), some kind of controls (buttons, accelerometer) and for the multiplayer things — some means of communication. All this should come with simple to use libraries and pre-packaged graphics, so that people can make something nice fast.

The display for games should't have too big of a resolution, so that you won't need to push a lot of pixels to update it, and it should be fast, so that you can do animations and so on. Of course there are games like 2048 or sudoku that will work on slow displays too.

Schedule

This is my initial idea for this project, but as you can see, it got relegated to quite a low priority by now. If you are giving the participants badges, you may as well include the talk schedules on them. With the ability to mark which talks they want to go to. And possibly with a real time clock and notification functions. The ability to update the schedule when there are changes in it would be nice too.

This requires some means of displaying text, preferably a monochrome display with relatively large resolution. It doesn't have to be fast, but should be able to do partial updates in less than 1 second. It doesn't have to be bright or large — you will use it while staring at it up close.

This really conflicts with the other goals, so I'm really not sure about it anymore. I guess it explains why no other badge does it.

Appearance

We still want it to look nice and be appealing to non-technical audience, of course, but I can see to way to make you wear it outside of the conference, considering the size requirements and the big place for your name on it. So no accessories, no watches, no hair ornaments, jewelry, etc. — it's going to be a badge and it's going to look like a badge.

Hardware Hacking

The number of people who are going to actually connect anything to their badges is going to be small probably — there are so many other things you can do at a conference. But adding a breadboard-friendly pin header somewhere should be easy, so why not do it. This is also a way to provide extension modules with additional sensors and devices that didn't fit in the budget for everyone, but are interesting to more advanced users.