Meter Communication Settings¶

Document Context¶

Purpose: Configure serial communication interface between device and smart meter
When to use: For meter setup, protocol configuration, encryption/authentication setup, or communication troubleshooting
Prerequisites: Knowledge of meter type and protocol; understanding of serial communication parameters
Related to: Meter protocols (DLMS, DSMR, MBUS), serial interfaces, encryption setup
Validates against: Real meter communication with Landis+Gyr and other meter types

Key Facts¶

Endpoint: /api/v1/meter/settings
Methods: GET, POST, PUT
Authentication: Required when device Web UI password is set
Supported protocols: DLMS, DSMR, MBUS, KMP, MEP
Interface types: P1, MBUS, TTL, MEP, UART, auto-detect
Auto-detection: Automatic baudrate and protocol detection available
Encryption support: DLMS encryption with 32-character hex keys
POST vs PUT: POST replaces all settings, PUT updates only specified fields

Endpoint details¶

Configure communication parameters with the connected meter, including serial port settings and physical layer configuration.

Endpoint	`api/v1/meter/settings`
Method	GET, POST, PUT
Response content type	application/json

Authentication

When a Web UI password is set, HTTP endpoints require HTTP authentication.

Firmware 1.10.X and later: Uses HTTP Digest authentication - Server challenges with WWW-Authenticate: Digest … (realm is the device hostname) - Algorithm: MD5-sess (device advertises MD5-sess; integrity variant supported) - qop: auth (and optionally auth-int for requests with body integrity) - Nonce and opaque are issued by the device; the client must include cnonce and increment nc - Expired nonce: server may return 401 with WWW-Authenticate: …, stale=true. In that case, retry the same request once using the new server challenge, a new cnonce, and reset nc=00000001.

Firmware before 1.10.X: Uses HTTP Basic authentication - Server challenges with WWW-Authenticate: Basic realm="..." - Credentials are base64-encoded in Authorization: Basic <encoded-credentials>

Recommended approach: Use --anyauth in curl to automatically detect and use the appropriate method:

curl --anyauth -u ":<password>" http://whatwatt-ABCDEF.local/api/v1/system

Configuration Fields¶

Field	Type	Default	Range/Allowed values	Description
`.baudrate`	uint	115200	300..115200	Data transfer rate over serial interface
`.parity`	string	none	none, odd, even	Parity control for serial transmission
`.stop_bits`	string	1	1, 1.5, 2	Number of stop bits in serial transmission
`.buffer_size`	uint8	64	1..128	Serial RX buffer size (bytes)
`.method`	string	Passive Push	Passive Push	Data acquisition method
`.encryption`	boolean	false		Enable data encryption at logical layer
`.encryption_key`	string	empty	32 hexadecimal characters	Data encryption key (GET hides the value; send 32 zeros to clear)
`.authentication_key`	string	empty	32 hexadecimal characters	Meter authorization key (GET hides the value; send 32 zeros to clear)
`.tx_invert`	boolean	false		Reverse polarity of transmission data line
`.rx_invert`	boolean	false		Reverse polarity of data receiving line
`.auto_baudrate`	boolean	true		Automatic serial port settings detection
`.if_type`	string	auto	auto, p1, mbus, ttl, mep, irda, uart, p1_adapter, ttl_push	Physical interface type (auto-detect or manual)
`.protocol`	string	auto	auto, dsmr, hdlc, kmp, mep, mbus, mbtr	Logical protocol on the interface
`.if_mode`	string	auto	auto, push, pull	Interface I/O mode
`.conv_factor`	real	1	0.001..1000	Conversion coefficient for power/energy/current values
`.time_offset`	int	0	−2^31..231−1	Meter time correction in seconds
`.sync_time_offset_with_ntp`	boolean	false		Automatically adjust time offset based on NTP
`.scalers_set`	string	default	default, custom, lge570	Scaling scheme for meter values

Example Request¶

No authWith password

curl http://whatwatt-ABCDEF.local/api/v1/meter/settings

curl --anyauth -u ":PASSWORD" http://whatwatt-ABCDEF.local/api/v1/meter/settings

Update semantics¶

POST: Full replace. Fields not provided are reset to defaults (factory schema). Use when setting a complete configuration.
PUT: Partial update. Only provided fields are changed; others remain unchanged. Use for incremental tweaks.

Examples:

# Partial update (PUT): only change interface type and protocol
curl --anyauth -u ":PASSWORD" -X PUT \
  -H "Content-Type: application/json" \
  -d '{"if_type":"p1","protocol":"dsmr"}' \
  http://whatwatt-ABCDEF.local/api/v1/meter/settings

# Full replace (POST): provide a complete configuration block
curl --anyauth -u ":PASSWORD" -X POST \
  -H "Content-Type: application/json" \
  -d '{
        "baudrate":115200,
        "parity":"none",
        "stop_bits":"1",
        "buffer_size":64,
        "method":"Passive Push",
        "encryption":false,
        "rx_invert":false,
        "tx_invert":false,
        "auto_baudrate":true,
        "if_type":"auto",
        "protocol":"auto",
        "if_mode":"auto",
        "conv_factor":1,
        "time_offset":0,
        "sync_time_offset_with_ntp":false,
        "scalers_set":"default"
      }' \
  http://whatwatt-ABCDEF.local/api/v1/meter/settings

Example Response¶

{
  "baudrate": 115200,
  "parity": "none",
  "stop_bits": "1",
  "buffer_size": 64,
  "method": "Passive Push",
  "encryption": false,
  "rx_invert": false,
  "tx_invert": false,
  "auto_baudrate": true,
  "if_type": "auto",
  "protocol": "auto",
  "if_mode": "auto",
  "conv_factor": 1,
  "time_offset": 0,
  "sync_time_offset_with_ntp": false,
  "scalers_set": "default"
}

Configuration Examples¶

Manual Serial Configuration¶

{
  "auto_baudrate": false,
  "baudrate": 9600,
  "parity": "even",
  "stop_bits": "1",
  "if_type": "p1"
}

Enable Encryption (DLMS/COSEM)¶

{
  "encryption": true,
  "encryption_key": "0123456789ABCDEF0123456789ABCDEF"
}

Time Synchronization¶

{
  "time_offset": 3600,
  "sync_time_offset_with_ntp": true
}

Custom Scaling¶

{
  "scalers_set": "custom",
  "conv_factor": 1000
}

Interface Types¶

Type	Description
`auto`	Automatic detection of interface type
`p1`	P1 port (DSMR)
`mbus`	M-Bus interface
`ttl`	TTL level serial interface
`mep`	MEP (Meter Exchange Protocol)
`irda`	Infrared optical interface
`uart`	Generic UART
`p1_adapter`	External P1-to-UART adapter
`ttl_push`	TTL interface in push mode (hardware-driven stream)

Protocols¶

Protocol	Notes
`auto`	Auto-detect
`dsmr`	DSMR P1
`hdlc`	DLMS/COSEM HDLC framing
`kmp`	Kamstrup Meter Protocol
`mep`	MEP
`mbus`	M-Bus
`mbtr`	M-Bus transparent/raw

Interface Mode¶

Mode	Description
`auto`	Auto-select push/pull from interface/protocol
`push`	Device pushes frames; gateway listens
`pull`	Gateway actively polls the meter

Scaler Sets¶

Set	Description
`default`	Automatic scaling detection
`lge570`	Predefined scales for Landis+Gyr E570
`custom`	User-defined scaling (see custom scalers)

Encryption Keys

Keys are not returned in GET responses (they are hidden/masked)
Use 32 hexadecimal characters (128-bit keys)
To clear a key via POST/PUT, send 32 zeros (00000000000000000000000000000000)

Auto-Detection

auto_baudrate enables automatic detection of serial parameters
if_type: auto enables automatic interface type detection
Manual settings override auto-detection when disabled