dataliteRS

WiFi-to-RS232 bridge for Datalite DX-3200 LED display controllers, running on an ESP32-C3. Provides a web UI to compose and send multi-page content over the serial bus.

Format     Style     Blink     Configure

Architecture

graph LR
    subgraph User
        B["Browser"]
    end

    subgraph ESP32-C3["XIAO ESP32-C3"]
        direction TB
        WiFi["WiFi\nSTA / AP"]
        HTTP["HTTP Server"]
        NVS["NVS Flash\nSettings + Pages"]
        UART["UART\n4800 baud"]

        WiFi --- HTTP
        HTTP --- NVS
        HTTP --- UART
    end

    subgraph RS232["RS-232 Bus"]
        MAX["MAX3232\nLevel Shifter"]
        RJ45["2pin RS232"]
    end

    subgraph Display["DX-3200 Display"]
        C1["Controller 1"]
        C2["Controller 2"]
        CN["Controller N"]
    end

    B -- "WiFi" --> WiFi
    UART --> MAX --> RJ45 --> C1 --> C2 --> CN

    style ESP32-C3 fill:#1a1a2e,stroke:#0f0,color:#0f0
    style Display fill:#1a1a2e,stroke:#f80,color:#f80
    style RS232 fill:#1a1a2e,stroke:#888,color:#ccc
    style User fill:#1a1a2e,stroke:#08f,color:#08f

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Project Structure

graph TB
    subgraph firmware["dataliteRS — Firmware Crate"]
        main["main.rs\nUART + WiFi + Server init"]
        settings["settings.rs\nNVS-backed config"]
        state["state.rs\nPage state + persistence"]

        subgraph web["web/"]
            mod["mod.rs\nServer setup"]
            api["api.rs\nREST API"]
            ui["ui.rs\nSingle-page Web UI"]
        end

        main --> settings & state & web
        mod --> api & ui
    end

    subgraph sdk["datalite — Standalone SDK Crate"]
        lib["lib.rs\nDX-3200 protocol\nimplementation"]
    end

    api -- "uses" --> sdk

    style firmware fill:#0d1117,stroke:#58a6ff,color:#c9d1d9
    style sdk fill:#0d1117,stroke:#3fb950,color:#c9d1d9
    style web fill:#161b22,stroke:#58a6ff,color:#8b949e

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dataliteRS/
├── src/
│   ├── main.rs              # Entry point: UART, WiFi (STA/AP), web server
│   ├── settings.rs          # Persistent settings in NVS flash
│   ├── state.rs             # Display page state with NVS persistence
│   └── web/
│       ├── mod.rs            # HTTP server setup
│       ├── api.rs            # JSON API endpoints
│       └── ui.rs             # Embedded web UI
├── datalite/                # Standalone SDK (no ESP dependencies)
│   ├── Cargo.toml
│   └── src/lib.rs
├── build.rs                 # ESP-IDF build glue
├── sdkconfig.defaults       # ESP-IDF: stack size, WiFi AP
├── rust-toolchain.toml      # Nightly (ESP-IDF std)
└── .cargo/config.toml       # Target: riscv32imc-esp-espidf

Firmware (src/)

• WiFi — connects as a client (STA) to a configured network, falls back to AP mode (DatalitePanel / datalite123).
• UART — drives the RS-232 bus at 4800 baud on GPIO21 (TX) / GPIO20 (RX).
• Web server — embedded HTTP server with a JSON API and character-grid web UI.
• NVS persistence — all settings and page content survive reboots.

datalite SDK

The datalite/ directory is an independent, standalone crate with no ESP or embedded dependencies. It implements the DX-3200 serial protocol and can be used in any Rust project that has a std::io::Write sink (serial port, TCP socket, file, etc.).

use datalite::Display;

// 2 controllers, 8 lines each, 48 chars per line
let display = Display::new(2, 8, 48);
let mut serial = std::fs::File::create("/dev/ttyUSB0").unwrap();

display.commit_pages(
    &mut serial,
    &[
        display.page(1)
            .line(1, "Hello world")
            .brightness(17)
            .readtime_secs(5.0),
        display.page(2)
            .line(1, "Page two")
            .readtime_secs(3.0),
    ],
).unwrap();

The SDK supports multi-controller addressing, multi-page content, inline blink markers, brightness, scroll/fade effects, moving speed, bold text, scheduling, and clock sync. It has its own rust-toolchain.toml (stable) and build target (x86_64-unknown-linux-gnu) so it can be developed and tested independently with cargo test -p datalite.

Hardware

Components

Part	Role	Pic	Link
Seeed XIAO ESP32-C3	Microcontroller — runs the firmware, provides WiFi and UART		Link Aliexpress*
UART-to-RS232 converter (e.g. MAX3232 breakout)	Level-shifts 3.3V UART to RS-232 voltage levels for the DX-3200 bus		Link Aliexpress*
RJ45 cable (Only Way 1)	You can Cut it to use the External RJ45 Port to connect to TTL Converter		Link Aliexpress*
USB C Port (Only Way 2)	To Mount externally on the Device		Link Aliexpress*
Old USB C Cable (Only Way 2)	You can Cut it to power the External USB-C Port you installed		Link Aliexpress*

*These are Referal Links. I get a promotion when u use them.

Wiring

graph LR
    subgraph MCU["XIAO ESP32-C3"]
        TX["GPIO21 · TX"]
        RX["GPIO20 · RX"]
        V3["3V3"]
        GND1["GND"]
    end

    subgraph CONV["MAX3232 Converter"]
        TTL_TX["TTL TX IN"]
        TTL_RX["TTL RX OUT"]
        VCC["VCC"]
        GND2["GND"]
        RS_TX["RS-232 TX OUT"]
    end

    subgraph PLUG["RJ45 Connector"]
        DATA["Data"]
        GND3["GND"]
    end

    subgraph DX["DX-3200 Controllers"]
        BUS["RS-232 Bus"]
    end

    TX --> TTL_TX
    TTL_RX --> RX
    V3 --> VCC
    GND1 --> GND2
    RS_TX --> DATA
    GND2 --> GND3
    DATA --> BUS
    GND3 --> BUS

    style MCU fill:#1a1a2e,stroke:#58a6ff,color:#c9d1d9
    style CONV fill:#1a1a2e,stroke:#f0883e,color:#c9d1d9
    style PLUG fill:#1a1a2e,stroke:#888,color:#c9d1d9
    style DX fill:#1a1a2e,stroke:#f80,color:#c9d1d9

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UART runs at 4800 baud, matching the DX-3200 protocol.

Mounting Options

graph TB
    subgraph external["Option A — External Mount"]
        direction LR
        E_USB["USB-C\n5V Power"] --> E_ESP["ESP32-C3\n+ MAX3232"]
        E_ESP -- "RJ45 cable\nGND + Data" --> E_DISPLAY["Display\nRJ45 Port"]
    end

    subgraph internal["Option B — Internal Mount"]
        direction LR
        I_PSU["Display PSU\n5V rail"] -- "5V + GND\n⚠ Measure first!" --> I_ESP["ESP32-C3\n+ MAX3232"]
        I_ESP -- "direct wiring or\nRJ45 jack pins" --> I_BUS["Controller\nBus"]
        I_HOLE["Optional:\nUSB-C hole\nAntenna slot"] -.-> I_ESP
    end

    style external fill:#0d1117,stroke:#3fb950,color:#c9d1d9
    style internal fill:#0d1117,stroke:#f0883e,color:#c9d1d9

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External (outside the display housing)

Place the ESP32-C3 and RS-232 converter in a separate enclosure. Cut an RJ45 cable from the converter into the display's RJ45 port. Only GND and Data out have to be connected to the Screen. Power the ESP32-C3 via its USB-C port from any 5V source.

Internal (inside the display housing)

1. Mount the ESP32-C3 and converter board inside the display enclosure.

2. Connect the converter's RS-232 output directly to the controller bus (no RJ45 needed, or use the existing internal connector). You can either connect it to the first Controller or to the Ports of the RJ45 Jack. For me it was measuring GND against GND of the Controller Board and guessing Data. As only one of the other two wires was connected to the controller, it was obvious.

   
   

3. Tap 5V from one of the display's internal power supply to power the ESP32-C3 via its 5V pin (not USB-C). Measure first to Validate 5V!

   
   

4. Optional: Drill a small hole in the housing for the USB-C port — useful for reflashing firmware and debugging without opening the case.

   
   

5. Optional: Drill or route a slot for the WiFi antenna to improve signal as the housing is metal.

   
   

Now you have a clean future-proof setup which allows most importantly portability. For me that is why i choose it.

Building & Flashing

Prerequisites: espup, ldproxy, espflash.

cargo run --release

This builds the firmware and flashes it via espflash (configured as the runner in .cargo/config.toml).