LEW840x gateway firmware specification

The reference for the firmware on the LEW840x and the LEW840x with cellular: what it does, what it publishes, what you can set, and what it does not do yet. Every value on this page is the one the images ship with.

Gateway Fanstel LEW840F-M2-V3Built with ESP-IDF 6.0.2 and nRF Connect SDK 3.4.0Built and verified by Adsum Networks, September 2026

System

Element	Part	Role
Application host	ESP32 in the base, 16 MB flash	Runs the gateway: uplinks, MQTT, the console, configuration
Ethernet	LAN8720A PHY in the base	First uplink by default
Wi-Fi	The ESP32’s own radio	Second uplink
BLE card, M2 slot	nRF52840 card, with or without a power amplifier	Scans, filters against the whitelist, reports to the ESP32
Cellular card, LN slot, optional	nRF9160 card from the LN60G series	LTE-M or NB-IoT, carrying traffic for the ESP32

One image reads which cards are fitted at boot. Fitting a cellular card to a unit that had none is a setting and a reboot, and the configuration survives it.

Firmware images

Image	Runs on	What it is	How to have it
Uplink, two ways out	ESP32	Ethernet and Wi-Fi	Free
Uplink, three ways out	ESP32	Ethernet, Wi-Fi and cellular	Free account
BLE scanner	nRF52840 card	One image for the amplified card, one for the plain card	Free
Cellular bearer, demo	nRF9160 card	The modem, carrying traffic, limited use for evaluation	Free account
Cellular bearer, production	nRF9160 card	The same bearer with no limit	Licence, on request
Source	All three chips	The BLE scanner and the two-way ESP32 application are free; the full source with cellular is licensed	Free, or on request

Every image comes with a manifest of SHA-256 hashes. The installer checks all of them before it writes any, and a mismatch stops the install with nothing written.

Flash the BLE image that matches the card. The plain image on an amplified card leaves the amplifier in bypass: no error, just far fewer advertisements heard. The boot log names which image is running.

Uplinks and failover


Order	Ethernet, then Wi-Fi, then cellular. Set it yourself; it applies live, with no reboot
Carrying	One uplink at a time. The others stay ready, holding an address
Hold-down	A link must stay up 5 seconds before traffic moves to it (`failover.holddown_ms`)
Measured failover	Ethernet cable out to stream resumed on Wi-Fi: 15.4 seconds, read at an independent subscriber
Return	When a better link comes back, traffic returns to it unprompted
Connectivity watchdog	With no working uplink for 10 minutes, the gateway restarts itself (`wd.reboot_min`, 0 turns it off)

BLE scanning


Filtering	On the BLE card, against a whitelist the ESP32 owns. A device that is not listed never crosses to the ESP32
Whitelist	Up to 64 addresses. An empty whitelist observes everything, which is the way to start
Measured	About 110 advertisements a second received; zero frame errors on the card link over 60 seconds; RSSI of −44 dBm from a tag at arm’s length on the amplified card
Card health	The console shows when the card was last heard from, so a quiet room and a dead radio do not look alike

MQTT


Broker	Your host and port (`mqtt.host`, `mqtt.port`, default 1883), with optional user and password
Transport	Plain TCP in this build
Client id	Configurable (`mqtt.client_id`)
Keepalive	60 seconds (`mqtt.keepalive`)
Topic prefix	Every topic starts with `mqtt.topic_prefix`
Last will	`<prefix>/status`, payload `offline`; both configurable

Each advertisement, on Ethernet and Wi-Fi, to <prefix>/adv:

{ "mac": "D2:14:97:21:15:C9", "type": 1, "rssi": -52, "ts": 815220, "adv": "0201060303aafe" }

type is the address type, ts when the gateway heard it in milliseconds, and adv the raw advertisement in hex. A digest, on cellular, to <prefix>/adv/digest, one message per interval (60 seconds by default) with one entry per device heard:

[{ "mac": "D2:14:97:21:15:C9", "count": 58, "best": -48, "last": -55, "first": 815220, "last_seen": 874910 }]

On cellular the gateway sends digests rather than every advertisement, because every byte is billed.

Cellular data budget


Counted	Only while cellular is carrying. Ethernet and Wi-Fi traffic never counts against it
Cap	`data.cap_mb`, 50 MB by default
At the cap	`data.on_exceed`: `sampled` keeps sending digests (the default), `drop` stops publishing
Network	`lte.network`, LTE-M by default; `lte.roaming` off by default; APN and SIM PIN if your SIM needs them
Standby cost	A cellular link that carries nothing still spends roughly 4 kB an hour in keepalives

The console

Served by the gateway from its own flash, on port 80. No app, no cloud account, nothing to install. It covers the overview, network and uplink order, MQTT, the scanner and whitelist, and status.


First power-up	On a wired network with DHCP: the console is at the address the network gives the gateway. Enter your network, broker and uplink order, then save
A change that strands the unit	A configuration change must be confirmed. One that is not confirmed within 90 seconds rolls back on its own
Backup	The configuration exports and imports, from the console or the API

The same data is available over HTTP to your own tools:

Endpoint	What
`GET /api/state`	Uplinks, the broker connection, the scanner, counters
`GET /api/config`	The configuration
`POST /api/config`, `/commit`, `/confirm`, `/rollback`	Change the configuration, safely
`GET /api/config/export`, `POST /api/config/import`	Back up and restore
`GET /api/devices`	Devices heard, with RSSI
`GET /api/whitelist`	The whitelist
`GET /api/transitions`	Recent uplink changes

Configuration

Group	Settings
Identity	`identity.name`, `identity.site`
Ethernet	`eth.enabled`, `eth.dhcp`, static address, netmask, gateway, two DNS servers
Wi-Fi	`wifi.enabled`, `wifi.ssid`, `wifi.password`, `wifi.security` (WPA2 by default), DHCP or static
Cellular	`lte.enabled`, `lte.network`, `lte.apn` with user, password and auth, `lte.sim.pin`, `lte.roaming`
Failover	`failover.priority`, `failover.holddown_ms`
MQTT	`mqtt.host`, `mqtt.port`, `mqtt.user`, `mqtt.pass`, `mqtt.client_id`, `mqtt.keepalive`, `mqtt.topic_prefix`, `mqtt.lwt_topic`, `mqtt.lwt_payload`
Data	`data.cap_mb`, `data.on_exceed`
Time	`time.ntp` (`pool.ntp.org` by default), `time.timezone`
Watchdog	`wd.reboot_min`

Most settings apply live. Network type, roaming and the time server apply on the next reboot. Flashing a new image without erasing keeps the configuration.

What this build does not do yet

No over-the-air updates. The flash is laid out for them, with two application slots, but there is no update path yet.
No TLS to the broker. The connection is plain TCP. See CRA readiness.
No switch between LTE-M and NB-IoT from the console. It is set on the modem, and the console shows the setting disabled with the reason.
No GNSS. The cellular card carries a GNSS receiver, and this firmware does not use it.
The cellular demo is limited. It is for evaluation; the production bearer has no limit.

LEW840x: flash it or build it

The gateway, the console, and building it from scratch.

LEW840x with cellular

Three ways out, what to order, and the failover walked on the board.

Get started

How it works

What it does

Supported hardware

Build on partner open hardware

Reference

About

LEW840x gateway firmware specification

System

Firmware images

Uplinks and failover

BLE scanning

MQTT

Cellular data budget

The console

Configuration

What this build does not do yet

LEW840x: flash it or build it

LEW840x with cellular

​System

​Firmware images

​Uplinks and failover

​BLE scanning

​MQTT

​Cellular data budget

​The console

​Configuration

​What this build does not do yet

LEW840x: flash it or build it

LEW840x with cellular

System

Firmware images

Uplinks and failover

BLE scanning

MQTT

Cellular data budget

The console

Configuration

What this build does not do yet