Your water meter already talks. AquaBridge listens.
A ~10 € receiver that picks up the encrypted radio telegrams of your wireless M-Bus water meter,
decrypts them locally and hands clean sensors to Home Assistant. No cloud, no gateway, no subscription.

_{ESP32 + CC1101 · ESPHome · tested on a Diehl Hydrus 2.0 (Type 173) · works with most wM-Bus meters that wmbusmeters knows}

Quick start · Parts · Wiring · Flashing · Home Assistant · Troubleshooting · How it works · Deutsch · Support

---

Why

A lot of water meters installed in the last years have a radio inside. Twice a minute they shout their reading into the air on 868 MHz so the utility can collect it once a year by driving past the house. The telegram is encrypted, but the key belongs to your meter, and most utilities hand it out if you ask nicely.

With that key and about 10 € of hardware you get your own water consumption in Home Assistant: every litre, every hour, every day. You see when the toilet keeps running, you get a push when a pipe bursts, and the Energy dashboard finally shows water next to electricity.

I built this for the Diehl Hydrus in my basement. It took one evening and a few surprises, all of which are written down here so it takes you less.

What you get

💧 Meter reading	the register of the meter, 1 litre resolution, updated every ~20 seconds
📈 Consumption	today / this month / this year, plus long-term statistics and the Energy dashboard
🚿 Flow	litres per minute, derived from the register (the meter does not send it)
🌡️ Water temperature	measured inside the meter, handy as a frost warning
🔋 Battery life	remaining years reported by the meter
📅 Billing date	reading at the last billing date and usage since then
🚨 Leak alarm	burst pipe, water running for hours, usage all night, frost. Push to your phone
📡 Watchdog	push when the receiver is offline or the meter goes silent
🔐 Local & encrypted	AES decryption on the ESP32, encrypted API to Home Assistant, nothing leaves your network

Does it work with my meter?

You need three things:

1. A wireless M-Bus meter on 868 MHz sending in mode T1 or C1. Most European water meters do. Look for "wM-Bus", "OMS", "868 MHz" or a little radio symbol on the display.
2. A driver in wmbusmeters. The ESPHome component uses its drivers: Diehl Hydrus / IZAR, Kamstrup Multical 21, Apator, Itron, Sensus, Zenner, Techem and many more.
3. The AES key if the telegrams are encrypted (almost always). See docs/03-aes-key.md, including a letter template for your utility.

Tested	Result
Diehl Hydrus 2.0, Type 173, version 0x76, T1, AES mode 7	✅ every telegram decoded, total / billing date / temperature / battery

If you get it running with another meter, open an issue or a PR and I'll add it to the table.

What you need

Part	What I bought	Price (Nov 2026)
ESP32 board	diymore ESP32 NodeMCU, USB-C, CH340, pack of 2	11.98 €
868 MHz radio	CC1101 868 MHz wireless transceiver, pack of 2	6.99 €
Case (optional)	ESP32 + CC1101 Case (USB-C Devkit) by danoman, CC0	~1 € filament
Power	any decent USB charger 5 V / ≥ 1 A and a short cable	–

Why exactly these parts, what to watch out for and alternatives: docs/01-hardware.md.

Important

Buy the 868 MHz version of the CC1101. The 433 MHz modules look identical but are tuned for the wrong band and will hear almost nothing.

Quick start

1. Get the AES key of your meter from the utility          -> docs/03-aes-key.md
2. Wire the CC1101 to the ESP32 (8 wires, 3.3 V!)          -> docs/02-wiring.md
3. Install ESPHome:          pipx install esphome
4. Clone this repo:          git clone https://github.com/Secoolioo/AquaBridge.git
5. cd AquaBridge/esphome && cp secrets.example.yaml secrets.yaml   (fill it in)
6. Set your meter ID in aquabridge.yaml (label "8 DME76 1234 5678" -> 0x12345678)
7. Plug the ESP32 into USB:  esphome run aquabridge.yaml --device /dev/ttyUSB0
8. Put the receiver close to the meter, watch the logs      -> docs/04-flashing.md
9. Home Assistant finds it: Settings -> Devices & services -> ESPHome -> Configure
10. Add helpers, automations and the dashboard              -> docs/05-home-assistant.md

The whole thing, step by step, with every command and the log output you should see: docs/04-flashing.md.

Wiring

CC1101	ESP32	Purpose
VCC	3V3	power, 3.3 V only
GND	GND	ground
SI / MOSI	GPIO13	SPI data to the radio
SO / MISO	GPIO12	SPI data from the radio
SCK	GPIO14	SPI clock
CSN	GPIO2	chip select
GDO0	GPIO5	"FIFO has data" interrupt, required
GDO2	GPIO4	not used, can stay connected

More photos, soldering tips and the antenna: docs/02-wiring.md.

Flashing

pipx install esphome
cd AquaBridge/esphome
cp secrets.example.yaml secrets.yaml      # WiFi, AES key, API key
esphome config aquabridge.yaml            # must say "Configuration is valid!"
esphome run aquabridge.yaml --device /dev/ttyUSB0

The first build downloads the ESP-IDF toolchain (a few GB, 10–20 minutes). After that a build takes a minute. On the first boot you should see:

[C][wmbus.transceiver]: Transceiver: CC1101
[C][wmbus_meter]:   ID: 0x12345678
[C][wmbus_meter]:   Driver: hydrus
[I][wmbus]: Receiver task created

Everything about the first boot, finding your meter in the air and reading the decrypted JSON: docs/04-flashing.md.

Home Assistant

_{The included dashboard, shown with example values.}

The ESP32 shows up as a new ESPHome device. Enter the API key from your secrets.yaml and you get:

Entity	Example
sensor.water_meter_total	1234.567 m³
sensor.water_meter_total_at_billing_date	1136.137 m³
sensor.water_meter_usage_since_billing_date	98.430 m³
sensor.water_meter_water_temperature	13.8 °C
sensor.water_meter_battery_life	10.4 a
sensor.water_meter_meter_signal	-37 dBm
sensor.water_meter_last_telegram	12 seconds ago
binary_sensor.water_meter_meter_reception	Connected

On top of that this repository ships ready-to-use Home Assistant configuration:

File	What it does
homeassistant/packages/aquabridge.yaml	water today / month / year, flow in m³/h, "water running" and "used without a break"
homeassistant/automations/leak_alarm.yaml	burst pipe, running for 2 h, night usage, frost. Critical push on iPhone
homeassistant/automations/reception_watchdog.yaml	receiver offline / meter silent / back again
homeassistant/dashboard/water-dashboard.yaml	complete dashboard with 3 views, built-in cards only

All of it explained, including the Energy dashboard and the UI way without YAML: docs/05-home-assistant.md.

Things I learned the hard way

• Distance matters more than you think. On my desk two floors up the receiver caught the meter, but every frame had a few bit errors and was silently dropped. In the basement, half a metre from the meter, 100 % of the telegrams arrive at -32 to -40 dBm.
• meter_id must be hex. 0x12345678, not 12345678. The decimal version becomes a different ID and nothing ever matches.
• Cheap ESP32 boards can have flaky flash chips. Mine has an XTX XT25F32B. On a weak USB charger, over-the-air updates corrupted the flash and once even wiped the bootloader. On the PC's USB port everything is fine. Details and the 1-minute fix in troubleshooting.
• version_4 of the component no longer works with current ESPHome (boot loop). Use the main branch, pinned to a commit, as in aquabridge.yaml.
• "UNKNOWN_80" is not an error. Diehl uses vendor-specific status bits. The leak detection here works with the flow instead.

How it works

The CC1101 is tuned to 868.95 MHz and listens for the wM-Bus sync word. Each T1 frame is 3-of-6 encoded; the ESP32 decodes it, checks the CRCs, verifies the CMAC and decrypts the payload with AES-128. The wmbusmeters driver then turns the DIF/VIF records into named values like total_m3. The long version: docs/07-how-it-works.md.

Repository layout

AquaBridge/
├── esphome/
│   ├── aquabridge.yaml          # the firmware configuration
│   ├── secrets.example.yaml     # copy to secrets.yaml
│   └── debug-snippets.yaml      # raw frames + decoded JSON for commissioning
├── homeassistant/
│   ├── packages/aquabridge.yaml # helpers as YAML package
│   ├── automations/             # leak alarm, reception watchdog
│   └── dashboard/               # water dashboard
├── docs/                        # the full guide, 01 to 07
└── images/

Credits

• SzczepanLeon/esphome-components: the wM-Bus radio and meter components for ESPHome. AquaBridge is a configuration and a guide built on top of it.
• wmbusmeters: the meter drivers and the decryption.
• ESPHome and Home Assistant.
• Case: ESP32 + CC1101 Case (USB-C Devkit) by danoman (CC0).

License

MIT. Use it, change it, sell your water meter receivers at the flea market. Your AES key and your meter data stay yours: never commit secrets.yaml.

Support the project

AquaBridge is free and open source. If it saved you an evening (or a flooded basement), a small tip is appreciated.

Solana (SOL):

71ZN1AtBvFASLmbnh7WkfhzYYBC35h9tAm7Awvvk9FPt

A ⭐ on the repository helps too.