Device (ESP32-C6)

Overview

The WattWächter is based on the ESP32-C6 microcontroller and reads energy data from your smart meter via an IR reading head. Data is stored locally and made available via REST API, MQTT, or the cloud portal.

Specifications

Property	Value
Microcontroller	ESP32-C6 (RISC-V, 160 MHz)
Connectivity	WiFi 6, Bluetooth 5.0 LE
Interface	IR reading head (SML protocol, D0 interface)
Power supply	USB-C, 5V
Storage	SPIFFS filesystem for history data
Status indicator	RGB LED
Hostname	ww.local (mDNS)

How It Works

Smart Meter ──IR──▶ WattWächter (ESP32-C6) ──WiFi──▶ Home Network / Cloud
                          │
                          ├── REST API (local)
                          ├── MQTT (Cloud / Smart Home)
                          └── LED status indicator

1. The IR reading head receives SML telegrams from the smart meter
2. The ESP32-C6 parses OBIS codes (e.g., 1-0:1.8.0 for total consumption)
3. Data is stored in SPIFFS (HighRes: 15 days, LowRes: 1 year)
4. Served via REST API and/or MQTT

LED Status Indicator

The RGB LED shows the current device status. When multiple states are active simultaneously, the one with the highest priority is displayed.

Status	Color	Mode	Priority	Meaning
OK	Green	Solid	1	Normal operation, everything fine
Startup	Yellow	Solid	2	Device starting
Info	Yellow	Dimmed	3	Information message
BLE active	Blue	Pulsing	4	Bluetooth waiting for connection
BLE connected	Magenta	Pulsing	5	Bluetooth device connected
OTA active	Magenta	Solid	6	Firmware update in progress
Error	Red	Pulsing	7	Error occurred
Reset pending	Red	Solid	8	Factory reset in progress

Disable LED

The LED can be disabled via the API:

curl -X POST http://ww.local/api/v1/settings \
  -H "Authorization: Bearer WRITE_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"ledEnable": false}'

Data Collection

OBIS Codes

The WattWächter reads the following values from the smart meter:

OBIS Code	Description	Unit
1-0:1.8.0	Total consumption (import)	kWh
1-0:2.8.0	Total feed-in (export)	kWh
1-0:16.7.0	Current power	W

History Storage

Resolution	Interval	Retention	Data
HighRes	15 minutes	15 days	Import, export, power, deltas
LowRes	1 day	1 year	Daily import, daily export

Authentication

The API uses two token types:

Token	Permission	Usage
READ Token	Read	Fetch data, check status
WRITE Token	Write	Change settings, start OTA, reboot

Tokens are passed in the header:

Authorization: Bearer YOUR_TOKEN

Disable API Auth

For local development, authentication can be disabled:

curl -X POST http://ww.local/api/v1/settings \
  -H "Authorization: Bearer WRITE_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"api_auth_required": false}'

Not recommended for production use.

MQTT Integration

The WattWächter can send telemetry data via MQTT to a broker (e.g., for Home Assistant or ioBroker).

Configuration

curl -X POST http://ww.local/api/v1/settings \
  -H "Authorization: Bearer WRITE_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"mqtt": {"enable": true, "host": "mqtt.example.com", "port": 8883}}'

TLS with Custom CA Certificate

For MQTT brokers with a self-signed certificate, a custom CA certificate can be uploaded:

curl -X POST http://ww.local/api/v1/mqtt/ca \
  -H "Authorization: Bearer WRITE_TOKEN" \
  -H "Content-Type: text/plain" \
  --data-binary @my_broker_ca.pem

Troubleshooting

Device Not Reachable

1. Check LED status (see table above)
2. Test ping: ping ww.local
3. Look up IP address in your router
4. If LED is solid red: restart device (disconnect/reconnect USB)

No Meter Data

1. Is the IR reading head correctly placed on the optical interface?
2. Does your smart meter have an unlocked PIN? (Some meters require data output to be enabled by the grid operator)
3. Check current values: curl http://ww.local/api/v1/history/latest

Factory Reset

Hold the reset button for 10 seconds. The LED turns solid red, then the device restarts in setup mode. All settings are reset.