Custom Firmware Round-Up: Stock vs H.J. Berndt vs ats-mini GitHub Fork

Three Main Firmware Paths

Understanding the actual lineage here matters — these aren't three totally independent projects, they share common ancestry but have diverged in features and priorities.

Stock AMNVOLT Firmware

What ships on the device from the manufacturer by default. Functional and stable, but doesn't track the community fork's rapid feature development — if you want the latest features (WiFi station database downloads, expanded memory slots, RDS, experimental Bluetooth), you'll want to move off stock firmware eventually.

The Community Fork: esp32-si4732/ats-mini

The actively-maintained, most feature-rich option, documented at esp32-si4732.github.io/ats-mini. Traces its lineage from Dave (G8PTN)'s original ATS Mini firmware, itself building on Ralph Xavier's port of PU2CLR (Ricardo Caratti)'s OLED_ALL_IN_ONE sketch for the SI4735/SI4732 chips — genuinely deep open-source hobbyist lineage. Current maintainers (Max Arnold/R9UCL and Marat Fayzullin) ship frequent releases with real ongoing feature additions: Scan mode, expanded memory, RDS, WiFi web UI with atsmini.local mDNS access, EiBi shortwave schedule database integration, experimental Bluetooth LE control. This is the option most active tinkerers gravitate toward.

H.J. Berndt's Version

A separate, actively-developed alternative specifically noted by AMNVOLT (the V4 manufacturer) as hardware-compatible with V4 without requiring any soldering or board modification. Notable features called out in recent updates include quick frequency entry via numpad-style input and expanded 64-slot station memory (up from the more common 32). Worth trying specifically if numpad-style direct frequency entry matters to your workflow — it's a genuinely different UX choice than the encoder-centric interaction model the community fork emphasizes.

Which Should You Actually Install?

• Stick with stock if you just want a working radio and don't care about ongoing new features — genuinely fine for casual listening.
• Go with the esp32-si4732/ats-mini community fork if you want the most actively developed feature set, WiFi/web UI capability, and you're comfortable following a GitHub-based release/changelog workflow to stay current.
• Try H.J. Berndt's version if the numpad frequency entry and larger memory slot count specifically appeal to you, or if you've seen it recommended in a specific community context relevant to your use case.

Switching Between Them

All three are flashed via the same underlying esptool.py/Flash Download Tool process (see the flashing guide) — nothing stops you from trying one, backing it up, and switching to another later if it doesn't suit your workflow. Just remember to back up your current firmware and settings before each switch, since some firmware transitions reset stored settings/memory slots (check the specific firmware's changelog/release notes for warnings about this before upgrading).

A Practical Suggestion

Given how easy backup/restore is with esptool.py, there's genuinely little risk in trying the community fork first (it has the most momentum and features right now), keeping your stock firmware backup safe, and reverting if you don't like it — the "worst case" here is a five-minute reflash back to where you started.