Minimal Tic Tac Toe Business Card

The PCB business card has long been a way for the aspiring electronics engineer to set themself apart from their peers. Handing out a card that is also a two player game is a great way to secure a couple minutes of a recruiter’s time, so [Ryan Chan] designed a business card that, in addition to his contact information, also has a complete Tic-Tac-Toe game built in.

[Ryan] decided that an OLED display was too expensive for something to hand out and an LED matrix too thick, so he decided to keep it simple and use an array of 18 LEDs—9 in each of two colors laid out in a familiar 3×3 grid. An ATmega328p running the Arduino bootloader serves as the brains of the operation. To achieve a truly minimal design [Ryan] uses a single SMD pushbutton for control: a short press moves your selection, a longer press finalizes your move, and a several-second press switches the game to a single-player mode, complete with AI.

If you’d like to design a Tic-Tac-Toe business card for yourself, [Ryan] was kind enough to upload the schematics and code for his card. If you’re still pondering what kind of PCB business card best represents you, it’s worth checking out cards with an updatable ePaper display or a tiny Tetris game.

Thanks to [Abe] for the tip!

38 thoughts on “Minimal Tic Tac Toe Business Card

  1. I see he has his finger bandaged in the video.
    I hope it wasn’t an injury caused by sharp edges somewhere on the card.
    (Something you don’t want to happen to a potential employer).

          1. I heartily agree. In *this* particular design, there’s no need to save those GPIO lines for anything else. Using a multiplexer would add a part to the BOM without making this device any better at what it does.

          2. @ Eric Weatherby, ” Using a multiplexer would add a part to the BOM without making this device any better at what it does.” What?? it would reduce part count.
            It’s not only about making it better or not, When someone asked you how you wired up those led’s and you told them individually. You at that moment just lost a potential client.

        1. > Somehow Mike thinks adding a part reduces part count…

          It does, it reduces by -1…

          42 – (-1) = 43…


          Although maybe charlieplexing would be the trick here… that reduces the pin count as well as the part count.

        2. Surely would have been better to do some really clever logic with a 555 timer or logic chip or whatever? This would have been a better dinner party talking point IMO. May even do this myself. And USB driven? Covert coin cell would have been better …. easy to do if the PCB is same thickness as a coin cell.

          1. Well, how would you do it coin powered? (Sincere question)(I mean how would you can put it in your wallet
            I have done a binary clock that charliplexes 24 leds (I think) with 5 pins. It has an attiny84 and a ds3231 for time keeping
            But the ds3231 needs a coin cell to keep time when the clock isn’t powered by usb.
            I haven’t found yet a solution that looks elegant, and I wouldn’t want to have a hole on the pcb for the coin cell
            I have been thinking about making a sandwich of pcbs, maybe to protect the components and to hide the coin

        3. Even without going so far as charlieplexing he could’ve wired the leds as a 3×6 matrix (6 because there are two colors for each cell), only requiring 9 gpio. In the end though I don’t fault him for using available hardware, just really depends on if his goal was optimization, hardware, software, low emi, etc.

          1. This could be done with 9 addressable RGB less. Then it only requires one pin and you get many possible colours. You could use red for one player, blue for the other and then green for showing which box is currently selected.

  2. Looks like someone forgot to remove component labels. The silkscreen looks really messy.

    I would remove the resistors from the display field, looks quite messy.

    Also, there would be numerous way to make the programming header less ugly.

    Here is an idea: How about using capacitive touch sensing instead of the button?

    Idea is inspiring, execution could benefit from more iterations.

      1. And if the PCB business card impresses the right person/people; it will be worth it in the long run!

        In other words, don’t leave an unattended bowl of them at a trade show!

    1. Yes it’s these small quantity hand assembled business cards that we need to worry about, not the billions of consumer electronics that are designed to have limited shelf life and are difficult/costly to repair.

  3. My ideal business card would have the following features:

    1. A PCB mounted solar panel.
    2. Rechargeable coin cell or bank of high powered capacitors or both.
    3. Buck booster charging circuit.
    4. Mini variable pitch buzzer / sounder.
    5. MCU
    6. WiFi chip.
    7. Push button.
    8. Instructions.

    These features then give you a whole range of possibilities ranging from quite fun to downright illegal.
    The fun thing to do would be to have it randomly make noises to remind your prospective employer of your existence. Just as a thought experiment, it could be turned into a WiFi hacking device through which you get access to the company computers and give yourself the job. DON’T DO THIS !!!! There are other things that could be done with this card that I deemed to be too extreme to mention. I’ll leave this to your imaginations, but feel free to guess if you feel so inclined.

    1. Step 1: Give out a bunch of these at a trade show.
      Step 2: Have them all connect to each other and synchronize their timing.
      Step 3: Have each one play a part of a pop song through their speaker.
      Now any recording of the event will be impossible to share online due to the copyrighted music playing in the background! Too extreme?

  4. It could be multiplexed, only 6 GPIOs would have to be used then. If you connect the LEDs in parallel but opposite: 3 GPIOs for rows, 3 for columns, and there, done. The additional feature is electromagnetic interference, that could play a melody on FM radio.

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