WaterMeter-FlowIQ2200 (ESP32 + CC1101 + Home Assistant MQTT Discovery)

Read Kamstrup FlowIQ 2200 (wM-Bus) using an ESP32 + CC1101, publish values over MQTT, and let Home Assistant create the device + sensors automatically via MQTT Discovery.

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What you get in Home Assistant

A single MQTT device with sensors such as:

• Water Meter Usage (m³) – total consumption
• Water Meter Month Start (m³) – month baseline
• Water Meter Flow (L/h) – current flow as an integer L/h (flow over 256 L/h may be temporarily wrong between full frames)
• Water Meter Flow (Full) (L/h) – flow from full frames (2‑byte), may be sporadic

See Flow behavior (compact vs full frames) below for how these values are derived.

Status

• Works with FlowIQ 2200 telegrams where AES key and meter ID are known.
• Publishes JSON to MQTT for easy HA sensors.
• ESP32: tested.
• ESP8266: experimental / untested.

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Flow behavior (compact vs full frames)

FlowIQ 2200 sends two frame types:

• Compact frames (CI=0x79) contain flow in 1 byte (0..255).
• Full frames (CI=0x78) contain flow in 2 bytes and are often much less frequent (minutes between).
  • Observed: full frames can be even more sporadic during evenings/weekends.

Readouts:

• FlowLph from compact frames (1‑byte VIF 0x32).
• FlowLphFull from full frames (2‑byte VIF 0x3B).

To get a usable flow value above 255, the firmware uses this rule:

• When a full frame arrives, its flow value is cached.
• While waiting for the next full frame, compact flow is extended by a +256 offset based on the last full frame.
• When a new full frame arrives with flow <256, the offset is reset.

This means FlowLph can look "stuck" high or low between full frames if the meter is quiet. This is expected and will update as soon as a new full frame arrives.

• Observed: full frames can be even more sporadic during evenings/weekends.

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License

This project is based on code from:

1. esp32-multical21 by pthalin
   Repository: https://github.com/pthalin/esp32-multical21
   License: GNU GPL v3 (or later)

That project is itself derived from:

2. esp-multical21 by chester4444
   Repository: https://github.com/chester4444/esp-multical21
   License: GNU GPL v3 (or later)

This project is GNU GPL v3 (or later).
See: LICENSE, CREDITS.md, and CHANGELOG.md.

Important: Original copyright headers are preserved in derived files.
All modifications are marked with: modified by erikxson, 2026.

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Hardware

• ESP32 Dev board
• CC1101 module (868 MHz)
• Antenna tuned for 868 MHz
• 3.3V power (do NOT use 5V for CC1101)

Wiring (ESP32 ↔ CC1101)

Important: CC1101 is 3.3V only. Do not power it from 5V.

This pin order follows the module silk-screen from VCC downward (as on the common green CC1101 boards):

CC1101 pin (top → bottom)	Connect to ESP32	Notes
VCC	3V3	3.3V only
GND	GND	common ground
MOSI	GPIO 23	SPI MOSI
SCK/SCLK	GPIO 18	SPI SCK
MISO	GPIO 19	SPI MISO
GDO2	(optional / not used)	leave unconnected unless your build uses it
GDO0	GPIO 32	data/interrupt pin used by firmware
CSN	GPIO 4	SPI CS

Right-side pads on many modules:

CC1101 pad	Connection	Notes
GND	GND	(optional)
ANT	Antenna wire	solder antenna here
GND	GND	(optional)

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Build & Flash (PlatformIO)

Open the project in PlatformIO

• Open VS Code
• Install PlatformIO (Extensions → search “PlatformIO”)
• In VS Code: File → Open Folder… and select the repo folder (watermeter-flowiq2200)
• Wait for PlatformIO to finish indexing dependencies

Create your credentials file (required)

• Rename src/credentials.example.h → src/credentials.h
• Fill in:
  • Wi-Fi SSID + password
  • MQTT broker host/IP
  • MQTT username/password (or empty strings if not used)
  • meterId (4 bytes)
  • key (16 bytes AES-128)

Verify wiring matches the firmware

• Confirm your wiring matches include/hwconfig.h

Select build target

• ESP32 (tested)
• ESP8266 (experimental / untested)

Build the firmware

• PlatformIO → Project tasks → select environment (esp32 recommended) → Build

Flash the firmware

• PlatformIO → Project tasks → select environment → Upload

Monitor serial output

• PlatformIO → Project tasks → select environment → Monitor

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Home Assistant

Enable MQTT Discovery and verify the device appears

Home Assistant must have the MQTT integration configured and connected to the broker.

Verify in Home Assistant:

• Settings → Devices & Services → MQTT
• Open the Devices list
• Look for a new device named similar to: Water Meter

You should get sensors such as:

• Water Meter Usage (m³)
• Water Meter Month Start (m³)
• Water Meter Flow (L/h)

MQTT topics (for verification)

Home Assistant: Settings → Devices & Services → MQTT → Configure → Listen to a topic

Listen to:

• watermeter/0/sensor/mydatajson
• watermeter/0/online
• watermeter/0/online_ts

MQTT control topics

Reset (new)

• Command: watermeter/0/cmd/reset
  Payload: true
• Status (retained): watermeter/0/cmd/reset/status
  Payload set back to false after processing.

Reset (legacy, still accepted during transition)

• Command: espmeter/reset
  Payload: true

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Runtime behavior (robustness)

• WiFi connection: retries up to 5 times with ~10s delay between attempts, then reboots.
• MQTT reconnect: 5s backoff between connection attempts.

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