I built a portable serial terminal for ESP32/Arduino in Rust — because my board kept resetting

코딩나우(하늘아래) — Fri, 12 Jun 2026 06:36:58 +0000

If you debug ESP32 boards over serial, you probably know this one: you flash the firmware, rush to open a serial monitor to catch the boot logs… and the act of opening the monitor resets the board. The DTR/RTS lines toggle on connect, the ESP32 auto-resets, and the first lines you actually wanted are gone.

I hit this enough times that I built my own terminal.

CNTerminal
Live + download: https://www.coding-now.com/en/cnterminal Source (MIT): https://github.com/cflab2017/tool_serial_terminal_Rust

It's a free, portable serial terminal for Windows — a single ~8 MB .exe. No installer, no runtime, no admin rights: drop it on a USB stick, run it on a locked-down lab PC, done.

What it does:

DTR / RTS control — the reason it exists. Keep DTR from toggling on connect and the ESP32 doesn't auto-reset, so you actually see the boot output.
HEX send & receive — for binary protocols, plus an ASCII ↔ HEX converter built in (no more alt-tabbing to a converter site mid-debug).
5,000-line auto-trim — long logging sessions don't slowly eat your RAM or lag the UI.
The usual: port/baud selection, timestamps, a dark amber CRT theme that's easy on the eyes during long sessions.
Why Rust + egui
I wanted a single file people could run anywhere, which ruled out anything with a runtime. Rust + egui turned out to be a great fit: the whole GUI app compiles to one small native binary, immediate-mode UI keeps the serial read loop and the rendering loop simple to reason about, and serialport-rs handles the device side.

The trickiest part wasn't the UI — it was making the serial reader thread, the auto-trimmed scrollback buffer, and the GUI repaint cooperate without dropping bytes at high baud rates. If you're curious, the source is MIT and pretty small.

Honest scope
Windows only for now (single-exe portability was the goal).
It's a terminal, not an IDE plugin — it does serial I/O well and nothing else.
If you live in a serial monitor — Arduino, ESP32, STM32, industrial gear over RS-232 — give it a try and tell me what's missing compared to your current setup. Feature requests and bug reports are very welcome, here or on GitHub.

5 free dev tools I built — no signup, no ads (most run entirely in your browser)

코딩나우(하늘아래) — Tue, 02 Jun 2026 03:41:17 +0000

I got tired of "free" online dev tools that bury you in ads, make you sign up, or quietly upload your data to a server just to format some JSON or resize an image. So over the last while I built a handful of small, single-purpose tools that fix that: no signup, no ads, and the web ones do everything in your browser — nothing is uploaded.

Sharing them here in case they're useful, and I'd genuinely love feedback on edge cases. I'm the author of all of these.

Web tools (100% client-side — your data never leaves the tab)

JSON Formatter & Validator → https://www.coding-now.com/en/json-formatter Pretty-print (2/4/tab) or minify, with a collapsible color-coded tree view. The part I use most: when JSON is invalid it points to the exact line:column of the error instead of a vague "unexpected token." Safe to paste API responses with tokens in them, since nothing is uploaded.
Image Format Converter (PNG · JPEG · WebP) → https://www.coding-now.com/en/image-converter Drag an image, pick a format, tweak quality, download. Handy for shrinking PNG screenshots to WebP, or flattening transparency before a JPEG export — all in the canvas, no upload.
Audio Cutter (trim to lossless WAV) → https://www.coding-now.com/en/audio-cutter Drop an MP3/WAV/M4A/OGG/FLAC, drag a region on the waveform, preview it, and export just that slice as WAV. Great for grabbing a clip without firing up an editor.
QR Code Generator (text · URL · WiFi · vCard + logo) → https://www.coding-now.com/en/qrcode Beyond plain URLs: generate WiFi QR codes (guests scan to join) and vCard contact QR codes, drop a logo in the center, and download PNG or SVG (the SVG embeds the logo too).

Bonus — a tiny desktop one

SnapLaunch (Windows) → https://www.coding-now.com/en/snaplaunch A portable tool that adds your favorite apps to the right-click menu of the Windows desktop/folders. No admin rights, single EXE. (This one's a native app, not a web tool — including it for completeness.)

Common thread: each is small, free, and respects your data — the web ones are a single static HTML file with zero dependencies. If you find a bug or a missing feature (especially in the JSON validator's error positions), I'd really appreciate hearing it in the comments.

DEV Community: 코딩나우(하늘아래)

I built a portable serial terminal for ESP32/Arduino in Rust — because my board kept resetting

5 free dev tools I built — no signup, no ads (most run entirely in your browser)