Shed on a vineyard block, 2 km from the house. Eight ESP32 nodes (soil moisture, a tank level, a pump relay) already talk MQTT to Hermetry fine when I test them at home.
At the shed there’s no network at all. My plan: Raspberry Pi 4 with a USB 4G dongle as uplink, the Pi’s own Wi-Fi as an access point for the ESP32s, and NAT between them. I’ve done hostapd + dnsmasq on Buster years ago and it was fiddly. Two questions: is that still the way on Bookworm, and would you trust a Pi doing this for years in a hot shed, or should I just buy one of the licensed routers?
How hot? We had a Pi 4 throttle at 80 C inside a steel box in summer.
Shed hits 45 inside in January. The box would be in the shade but still.
Both work, I have both in the field. On Bookworm it’s much less fiddly, NetworkManager does the AP and the NAT in one go:
sudo nmcli dev wifi hotspot ifname wlan0 ssid shed-iot password 'long-passphrase-here'
sudo nmcli con mod Hotspot connection.autoconnect yes ipv4.method sharedipv4.method shared hands out DHCP to the ESP32s and NATs them out of whatever has the default route, your 4G dongle. The Pi’s onboard Wi-Fi is fine for 8 clients at short range.
Where I’d think twice is heat and SD cards, plus nobody can reach the Pi when it hangs. If you go Pi: metal case as heatsink, a decent industrial SD or USB SSD, read-only root if you can, and the hardware watchdog enabled.
What a licensed router gives you on Hermetry for the money: you claim it with the code on its local Cloud page, it logs in with its own certificate, you can change its settings and update its firmware from Hermetry, and you can open its web panel from its device page without a fixed IP, which on a 4G link you won’t have. It’s a device in your org itself and counts once against the device limit. Remote access sessions are time-limited and audited.
My rule: one site I can drive to, Pi. Sites that need a ute and a day, licensed router. Details: Licensed gateways and Hermetry Edge.
Built the Pi version this weekend since I had the parts, the nmcli hotspot took ten minutes instead of the old afternoon. All eight nodes report. I’m going to price a licensed router for the far blocks though, the “open the panel without a fixed IP” bit is exactly what I’m missing on 4G. Thanks Neha.
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