ATS Mini V4: Flashing Custom Firmware From Your Phone (ats-mini vs H.J. Berndt)

The ATS Mini V4 (ESP32-S3 + Si4732) ships with the stock ESP32-SI4732 receiver firmware. Two community alternatives are worth flashing if you want more capability than the stock UI gives you — and both can be flashed straight from an Android phone, no PC required.

Phone Requirements

Android phone running Chrome or Edge (Web Serial API support required)
iPhone will not work — Web Serial isn't supported in iOS Safari or Chrome-on-iOS
USB-C to USB-C cable (or USB-C to micro/OTG adapter) to connect the ATS Mini to the phone
Some phones don't supply enough power over OTG for a stable flash — if the flash fails partway, try a powered OTG hub or a different cable

Option 1: ats-mini (esp32-si4732 / G8PTN fork)

Open source, actively maintained, broad feature set. Originally developed by Dave (G8PTN) building on Ralph Xavier's and PU2CLR's (Ricardo Caratti) work, now maintained by Max Arnold (R9UCL) and Marat Fayzullin.

EiBi broadcast schedule support
EEPROM backup/restore via the receiver's web interface
Web-based memory slot editor
VFO/BFO tuning mechanism for chuff-free SSB tuning across ~30kHz spans
Optional large S-meter / S+N-meter UI layout
Theme editor, RDS radiotext, per-band mode memory

Source and documentation: esp32-si4732.github.io/ats-mini

Flashing page (web installer, works in Chrome): esp32-si4732.github.io/ats-mini/flash.html

Option 2: H.J. Berndt Firmware

A German-developed, closed-source (binary-only) alternative aimed squarely at shortwave listeners and utility DXers. Leans "operator's tool" — fewer gimmicks, more on-radio decoding.

Built-in RTTY and CW (Morse) decoder — decoded text shown directly on the display, no laptop or audio cables needed
Multiple decode modes: Morse, RTTY, RTTY45, RTTY75, TONE/BL
Fast Tune mode for a classic "analog" scanning feel, with precision tuning still available on slow knob turns
ETM (Easy Tuning Mode): scans active bands, logs discovered stations, marks them on the display
AM Band Monitor: plots band occupancy over up to 5 hours
Numeric frequency entry (NUMPAD) via long-press on the TUNE menu item
64 memory slots, FM RDS with radiotext

V4-specific note: the V4 board already has hardware support for this firmware built in — no soldering or one-wire mod required (older V1–V3 hardware needed a small soldered mod to enable RTTY/CW decoding).

Official firmware page (German, use browser translate if needed): hjberndt.de/dvb/pocketSI4735DualCoreDecoder.html

Which One?

If you want in-radio RTTY/CW decoding, fast band scanning, and utility/DX-oriented tools, go with Berndt's firmware. If you want an open-source, actively-developed base with broader general-purpose features (EEPROM backup, memory web tool, themes), go with ats-mini.

Flashing Steps (Web Installer Method)

Plug the ATS Mini into your Android phone via USB-C cable
Open Chrome, navigate to the firmware's web flasher page
Tap Connect, select the ESP32-S3 device from the popup permission prompt
Choose the correct firmware variant for your hardware (V4) — flashing the wrong variant can damage the receiver
Press Program/Install and wait for the flash to complete
Power cycle the receiver and confirm the new firmware version under Menu → Settings → About

Warning: flashing a different firmware variant than your actual hardware (e.g. the LilyGO T-Embed variant on a standard AliExpress-style ATS Mini) can damage the receiver. Always confirm hardware version before flashing.

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