For this project, my co-worker - @descartez and I created an awesome tic tac toe game using the radio functionality of microbits. If you haven't heard of microbits before, they're an awesome microcontroller designed to teach kids programming. They have A TON of functionality including what we used for this project; the LED matrix, 2 buttons, and radio capability. The game works very simply, we have a 3x3 grid of worker mirco:bits that send a signal of either X or O to the master micro:bit who keeps track of all the win states and also resets the game. We were able to complete this project in less than 24 hours and displayed it during an event the next weekend where it was heavily used! And people seemed to really enjoy it! Obviously, as you follow along, you'll see where we had to cut some corners to get it done in time, but we think what we have so far is pretty rad. Show us your tic tac toe games, or any spots we could improve!

Supplies

Step 1: Materials

10 microbit controllers (All together this costs around $150, which is a lot! However, in our experience there are lots of these around, so don't be afraid to reach out to your community of makers, techies, and students.)
micropython IDE
Drill with 1/4 in bit
4 pieces of 12x24" 1/8 plywood
3 6m 20mm bolts
1 6m 40mm bolt
4 6mm nuts

Step 2: Game Design

Step 1: Deciding the rules for Tic Tac Toe

We used these

Step 2: Code for the worker :bits

Each worker :bit is given a coordinate.

(0,0) (0,1) (0,2)

(1,0) (1,1) (1,2)

(2,0) (2,1) (2,2)

This coordinate is adjusted in the top line of code for the worker:bits.
- coord_x = 0
- coord_y = 0
Each worker has two things. 1) When button A is pressed the LED matrix flashes X and a radio signal is sent to the master saying 'X was pressed on microbit (0,0)', and the same for button B.

Step 3: Code for the master micro:bit

The master micro:bit knows a bunch of things.
- It knows all the win states
  - Rows
    - (0,0)(1,0)(2,0)
    - (0,1)(1,1)(2,1)
    - (0,2)(1,2)(2,2)
  - Columns
    - (0,0)(0,1)(0,2)
    - (1,0)(1,1)(1,2)
    - (2,0)(2,1)(2,2)
  - Diagonals
    - (0,0)(1,1)(2,2)
    - (0,2)(1,1)(2,0)
- It knows that there are only 9 :bits, and that the game ends immediately after a win state is sent
- It can reset the game, and clear all the worker :bits
  - This is our workaround for pretty much all of the holes in the code, because we did this project so quickly. If there's a cat's game, the users are supposed to hit reset. Otherwise, we would have had to add in another chunk of code for all the Tie game states, and we just didn't have time to do that

Link to Descartez's code on Github

Step 3: Designing the Enclosure

I knew in making this project that I wanted to be able to display this, and that I might not have access to power. This was both a blessing and a problem because it meant that each micro:bit was going to need a battery connected. The easiest solution was to put everything in a box. For this, I generated one using makercase.com. I designed it large enough that it could hold the micro:bits and their batteries, as well as have some written instructions.

I also knew I needed support for the micro:bits to not fall in, so I laser cut a smaller piece to fit behind the micro:bits. This piece is secured screws. The backplate and the sides were glued together, but the top was left detached and only secured with the screws, so that I could access the inside as needed. I used tape to hold the interior panel in place. And to tape them to the front plate so that they didn't fall in or down.

It was a bit tricky, but I got all of the microbits plugged in with their batteries and taped in. On 3 corners I used smalled 6m screws to secure the front panel and the interior panel together. On the last corner, I used a longer screw to screw all the way through the box to hold the lid on.

Step 4: Playtesting

This game was a hit at our weekend event! Kids and adults both seemed to really enjoy trying to work out what was happening, as well as, what components were used. This project only took us an evening to put together, and it was well worth it. Show us your designs, and let us know what tweaks you made!