The Weather-Station Listener.

What it does.

Consumer weather stations are two parts: a sensor array outdoors and a display indoors, joined by a one-way radio link. The array does not know or care what receives it. This node is a second receiver. It hears the same broadcasts, decodes them with the same open decoders the rtl_433 project has built up over a decade for more than two hundred device types, and harvests every value each device sends: temperature, humidity, wind speed, gust and direction, rainfall, solar radiation, UV, soil moisture, leaf wetness, lightning strikes and distance, particulates, water leaks, battery state. Each device becomes its own stream at your endpoint under its own broadcast id, and each reading arrives in canonical units, so a mile-per-hour station and a metre-per-second station look the same to whatever reads them.

Nothing about the station changes. The display keeps working. The station keeps its batteries. No pairing, no app, no account, and the station’s maker never knows. That is the Collect layer applied to hardware you already paid for, and it is the question the Home Assistant forums have asked for years: how do I get my cheap weather station’s data without the vendor’s cloud? This is the answer, in one flash.

The decoders are not ours, and that is the point. They are the rtl_433 project’s, ported to the ESP32 as rtl_433_ESP. Our sketch wraps them as a driver on the shared OAT node core and maps what they decode onto the OAT vocabulary. A new station is a decoder upstream, not a sketch release. The one exception is deliberate: a board with a bare receiver on a pin cannot run those decoders, so that image carries a single hand-written one for the AcuRite 5-in-1, and the wiring section says exactly what that costs.

What it hears.

Two bands, one radio, one setting. In North America the AcuRite, La Crosse and Oregon Scientific families broadcast on 433.92 MHz; the Fine Offset family sold as Ecowitt and Ambient Weather broadcasts on 915 MHz. The radio hears one band at a time; the band is a setting on the setup page.

The shipped images decode on-off keying, which is how everything in the table transmits. The newest Ecowitt ultrasonic arrays, the WS80 and WS90, use FSK instead. The same radio can hear them, but not at the same time as the on-off stations, so that is a source build with one flag changed rather than a button on this page.

Every station heard is reported unless you say otherwise. On a shared band that includes the neighbours’ stations. If you want only yours, the allow-list on the setup page takes the ids you see under Stations heard and reports those alone.

Flash it.

Plug your board in, find it below, and press its button. The images differ by where the radio is wired, so pick the row that matches your build; the installer checks the chip matches before it writes anything.

Prefer the source? Browse it on GitHub: the full project, openly licensed, ready to build yourself.

What you need.

Under fifteen dollars if you already own the station:

What you do not need: a software-defined-radio dongle, a Raspberry Pi running rtl_433, a Linux box, or any of the vendor’s hubs. Those are the routes the forums usually end up on. This is one board and one module.

Wiring the radio.

The CC1101 is an SPI device: four data wires, two signal pins, power and ground. The pins below are what each image expects. On the Heltec V2 there is nothing to wire; the board’s own LoRa chip receives on-off keying and the image uses it.

Any other board with a bare receiver on a pin builds the same way from source: -DOAT_RX_DATAPIN=<gpio> selects the pulse-decoder path. It hears the AcuRite 5-in-1 today; adding another on-off-keying station to that path means writing its decoder by hand, which is exactly the work the CC1101 route avoids.

The CC1101 is a 3.3-volt part. Do not feed it 5 V. Keep the wires short, under 15 cm, since SPI at the module’s clock does not like long jumpers, and keep the module and its antenna away from the ESP32’s own Wi-Fi antenna where the board allows it. If the setup page says radio not found, it is one of: CSN on the wrong pin, MISO and MOSI swapped, or a module powered from 5 V that has already said goodbye.

How it works.

1. The station broadcasts, the way it already does. AcuRite every 18 seconds, Ecowitt every 16 to 64 depending on the sensor.
2. The radio watches the signal level on the band. When it jumps above the noise floor, the library captures the pulse train and hands it to the rtl_433 decoders, which try each protocol until one’s checksum passes.
3. The decoded message names the model, the station’s id, and its readings. This sketch turns the model and id into a stream id, maps each reading onto the OAT vocabulary with the unit converted, and folds it into that stream’s window.
4. On a timer, the node core pushes one signed batch to your endpoint, or publishes to your broker, exactly as every OAT gateway does. Every 60 seconds it sends its own heartbeat.

Because a station’s two message types arrive at different moments, and because a windy minute produces more wind readings than a calm one, everything continuous is averaged over the push window and everything cumulative or directional keeps its latest value. Rain arrives as the station’s running total, never as a delta, so a missed broadcast loses nothing and rainfall per hour is a subtraction at your endpoint. Wind direction is never averaged, because the mean of north and north-north-west is not a direction.

One more honest detail. The receiver on a five-dollar module is not as sensitive as a software-defined-radio dongle with a proper antenna; expect about half the range. For a station within a hundred metres and line of sight, that is no limit at all. For the far pasture, put the listener out there on a LoRa node.

Set it up.

The same one form as every OAT gateway, served by the device itself, plus two fields of its own.

1. Power the board from any USB charger. Join the Wi-Fi network OAT-Setup-XXXXXX (open, no password). A setup page opens by itself; if not, visit http://192.168.4.1.
2. Sign in, fill in a name, your Farm ID, the location, your Wi-Fi, and where the readings should go. Press Save & Connect.
3. Set the Band: 433.92 for AcuRite, La Crosse and Oregon Scientific; 915.00 for Ecowitt and Ambient Weather in the US. The radio retunes on the spot.
4. Watch Stations heard on the same page. Your station appears on its next broadcast with its model, signal strength, and how long ago. Give it a minute; a station that only broadcasts every 60 seconds needs one. A station that goes quiet for ten minutes is marked silent and its stream released; it files straight back in when heard again.
5. If the neighbours’ stations show up too, copy your station’s id into the allow-list and save. Only the listed ids are reported from then on.
6. Open the Status page and press Push now. A green “OK” means your station’s readings just reached your endpoint.

Ready to test it? Enter https://iot-test.openagriculturetechnology.com/ingest as the endpoint URL, then open the Open Agriculture Technology Test Endpoint and pick your farm. The listener appears as a gateway with your station and each sensor listed under it. It keeps about an hour of readings, enough to prove the chain before you point it at an endpoint you keep.

Open the printable setup card (PDF)

A three-page field card: what to have on hand, the flash and setup steps, blanks for this node’s settings and ids, the console commands, and the fixes for the usual snags. Print one per node.

What it sends.

Ordinary oat-ods, tagged oat-weather-listener. Each station or sensor is one stream named by its broadcast id, and every quantity it sends is one observation in canonical units with the aggregation stated.

{
  "schema": "oat-ods/0.3",
  "msg_type": "batch",
  "sent_at": "2026-09-05T15:12:00Z",
  "seq": 2000018,
  "source": { "tier": "oat-weather-listener", "gateway_id": "barn-wx",
              "farm_id": "willow-oaks", "fw": "OAT-Weather-Listener/1.0.0" },
  "messages": [
    { "observed_at": "2026-09-05T15:12:00Z",
      "stream": { "id": "acurite-5n1:2716" },
      "measurement": "wind_speed", "value": 2.34, "unit": "m/s",
      "agg": { "window_s": 60, "samples": 3, "method": "mean" },
      "source": { "physical_id": "acurite-5n1:2716", "brand": "AcuRite", "model": "Acurite-5n1", "rssi": -63 } },
    { "observed_at": "2026-09-05T15:12:00Z",
      "stream": { "id": "acurite-5n1:2716" },
      "measurement": "wind_direction", "value": 225, "unit": "deg",
      "agg": { "window_s": 60, "samples": 3, "method": "last" } },
    { "observed_at": "2026-09-05T15:12:00Z",
      "stream": { "id": "acurite-5n1:2716" },
      "measurement": "rain_total", "value": 128.52, "unit": "mm",
      "agg": { "window_s": 60, "samples": 2, "method": "last" } },
    { "observed_at": "2026-09-05T15:12:00Z",
      "stream": { "id": "acurite-5n1:2716" },
      "measurement": "temperature", "value": 27.4, "unit": "Cel",
      "agg": { "window_s": 60, "samples": 1, "method": "mean" } },
    { "observed_at": "2026-09-05T15:12:00Z",
      "stream": { "id": "fineoffset-wh51:0a3f" },
      "measurement": "soil_moisture", "value": 41, "unit": "%",
      "agg": { "window_s": 60, "samples": 1, "method": "mean" },
      "source": { "physical_id": "fineoffset-wh51:0a3f", "brand": "Fine Offset (Ecowitt / Ambient)", "model": "Fineoffset-WH51", "rssi": -71 } }
  ]
}

The whole format, every field and the full vocabulary are in the developer reference. If you write endpoints, the section on gateways that carry other sensors is the one that applies: a listener is a gateway pushing readings that are not its own, and the four rules there are all an endpoint needs.

Into Home Assistant.

This is the part people have been asking for. Choose MQTT as the delivery method on the setup page, point it at the broker Home Assistant already uses (the Mosquitto add-on, usually), and the listener publishes every stream with MQTT discovery messages. Home Assistant creates the entities by itself: one device per station, one sensor entity per reading, with the right device class and unit, so temperature shows as temperature and wind speed as wind speed with no YAML. Your AcuRite becomes a Home Assistant device within a minute of the first broadcast.

1. Install the Mosquitto broker add-on if you have not, and the MQTT integration. Note the broker’s address, user and password.
2. On the listener’s setup page choose MQTT, enter the broker, user and password, leave the topic prefix at oat. Save.
3. In Home Assistant open Settings, Devices & Services, MQTT. The station is there, named by its id, with its sensors beneath it. Rename it to something human; the id stays underneath.
4. Put the entities on a dashboard. The agricultural cards page has the wind rose and rain cards; the weather-station guide walks the whole thing with screenshots and the automations that make a station useful, frost warning first.

The same MQTT path feeds anything else that speaks MQTT: Node-RED, Grafana through Telegraf, a spreadsheet through a five-line script. And the webhook path feeds anything with a URL. The Home Assistant guide covers the other two ways a station reaches Home Assistant too, through an Ecowitt or Ambient hub or a Tempest hub, for people who already own one.

As a pod on a LoRa node.

The station is in the far field and there is no Wi-Fi there. Fine. This listener also prints every reading it hears on its USB serial port in the oat-line grammar, whether or not Wi-Fi is configured. Cable that port to the LoRa Field Node’s pod port with three wires, and every station this listener hears rides to the house over LoRa as a cluster of sensors on that node, under the same stream ids. Move the station to the barn later and the same board, with the Wi-Fi form filled in, pushes directly. Same firmware. The difference is configuration.

Why a second board rather than a decoder inside the field node? Because the decoders want a radio to themselves and a processor that is doing nothing else, and the field node is already reading probes and running its own radio. A pod does one job, and any board can be one.

Stations that talk to a hub instead.

Some stations do not broadcast to the air in a way this listener can use, or you already own the vendor’s hub and it is sitting on your network. Those feeds are still yours, and they arrive at your endpoint through a different door: the gather bridge, a small Python program that runs on the same machine as your endpoint or Home Assistant and turns a hub’s feed into oat-ods. Three sources are built in:

A hub feed needs no ESP32 at all. It is the right choice when the hub is already there. The listener is the right choice when you want the readings without the hub, or the station has no hub, or the station is out of Wi-Fi range.

Range, bands and honest limits.

• One band at a time. A farm with an AcuRite on 433 and Ecowitt soil probes on 915 needs two listeners, or one listener switched between bands. The radio cannot hear both at once.
• On-off keying or FSK, not both. The shipped images are on-off keying, which covers everything in the table. The Ecowitt WS80 and WS90 ultrasonic arrays are FSK and need the source build with the modulation flag changed.
• About half the range of an SDR dongle. A hundred metres with line of sight is comfortable; a metal barn between the station and the listener is not. Height and a wire antenna cut to the band buy more than anything in software.
• Stations that re-roll their id. A few models pick a new id every battery change. The history at your endpoint splits at that point; the endpoint’s map from id to place is where you reconnect it. Most models, including the AcuRite Iris and the Ecowitt family, keep their id.
• Davis is not on the list. Its frequency-hopping protocol is reverse-engineered and fragile. Use the WeatherLink Live hub through the bridge.
• Cloud-only stations. Netatmo and similar talk to their maker’s servers and nothing local. There is nothing here to hear.

For makers & trainers.