u/e4_user

Previous post: https://www.reddit.com/r/arduino/s/gtiHTDrmAk

The video file was too large to upload directly to Reddit, so I had to share it as a youtube link instead. Hope that's all right.

This video documents the journey of my split flap chess machine project from the very beginning to its completion. I compiled the progress clips I recorded along the way and arranged them in chronological order with their dates.

If you're interested in seeing how the project evolved over time, I hope you'll enjoy watching it.

I feel like I’ve probably milked this project enough for now. Once I’ve finished organizing the files and everything is ready to be open-sourced, I’ll be back with another update. Thanks again for all the support!

https://preview.redd.it/fuqvlw7sqh0h1.jpg?width=4000&format=pjpg&auto=webp&s=df5c0e2d4897a6a31eda09b6cfeea8deeb5d9eba

Previous post: https://www.reddit.com/r/arduino/s/1Wejy62eQ9

Hello everyone! I was really encouraged by all the support and interest on my last post. I’ve been working even harder than usual, so I think I’ll be able to show you a fully completed split flap chess board up to the 8th rank very soon.

This project can continue thanks to all of you as well. The reason I made my first post here was because I was feeling really exhausted and unmotivated, and I thought sharing my progress with others might help keep me going. But the response was far better than I expected, and now my motivation bar is completely full.

Anyway, enough of the introduction. In this post, I’d like to talk about the mechanism and technical details that many of you were curious about.

https://reddit.com/link/1ta0eob/video/18xk6a90rh0h1/player

First of all, the module shown in this video was specifically made so the internals are visible. You can see the motor mounted at the back, right? Since each module corresponds to one square on the chess board, the front surface area couldn’t be too large. Because of the size constraints, it wasn’t possible to place the motor directly next to the spool in a direct-drive configuration, so I mounted the motor behind the module and transmitted power through gears instead.

For the motors, I’m using 28BYJ-48 stepper motors converted to bipolar mode together with A4988 stepper drivers. The wires attached to the side of the module are for the Hall sensor, which detects a magnet embedded in a specific part of the spool to establish the home position.

The photo at the top shows the back side of the board. And yes, I know. It’s a mess. I wanted to organize the wires properly, but once bundled together they became too short to reach. Anyway, let me explain the overall structure.

In my previous post, I mentioned that I use an ESP32 as the main brain running the chess engine, along with several Raspberry Pi Picos responsible for each rank. It would be interesting to explain how they communicate and operate together as a single machine.

First of all, they communicate over UART. Initially, I tried using RS-485, but it turned out to be much harder than expected. Communication would randomly fail, chips would burn out, and after struggling with it for a while, I decided to switch to the much simpler UART approach.

Each Pico is responsible for one rank, so a full board will contain a total of eight Picos. Let’s say I move a knight from g1 to f3. In that case, the g1 square needs to change to an empty square, while the f3 square needs to change to a knight. The g1 square is controlled by Pico 1, while f3 is controlled by Pico 3. So how is this command transmitted?

https://preview.redd.it/4apbl8rfrh0h1.png?width=645&format=png&auto=webp&s=b0d87221ee436d5fc0fc7d6f76b76362e694e7da

As shown in the diagram above, the TX pin of the ESP32 is connected to the RX pin of Pico 1. Then Pico 1’s TX connects to Pico 2’s RX, Pico 2’s TX connects to Pico 3’s RX, and so on. Finally, Pico 8’s TX connects back to the RX pin of the ESP32.

Each Pico receives messages from the neighboring node. If the message is not intended for that Pico, it simply forwards it to the next node. If the message is addressed to that Pico, it both executes the command and forwards the message onward. Eventually, the message travels around the ring and returns to the ESP32, which verifies that the message was neither corrupted nor lost. If something is wrong, it retransmits the message; otherwise, the message is discarded.

So the knight move I mentioned earlier works like this:

The ESP32 sends out a command to update the board: “Set g1 to empty. Set f3 to knight.”

That message is immediately received by Pico 1. Since there is a command intended for it, Pico 1 changes g1 to an empty square. Of course, it still forwards the message to Pico 2.

Pico 2 has no commands intended for it, so it does nothing and simply passes the message to Pico 3.

Pico 3 receives the message and changes f3 to a knight.

The message then continues around the ring until it eventually returns to the ESP32, which verifies the integrity of the message and discards it.

https://preview.redd.it/4po10dzkrh0h1.jpg?width=4000&format=pjpg&auto=webp&s=1bf660d0f8136f4d5314c8c557f3db61a3d5846b

I think that explains the overall structure pretty well. I should probably get back to working on the remaining three ranks now. I can’t wait to show you the finished chess board as soon as possible.

I hope this answered at least some of your questions, and if there’s anything else you’re curious about, feel free to ask in the comments.

Thank you!