SPAN Panel API

A Python client library for the SPAN Panel v2 API, using MQTT/Homie for real-time push-based panel state.

v1.x Sunset Notice

Package versions prior to 2.0.0 are deprecated. These versions depend on the SPAN v1 REST API, which will be retired when SPAN sunsets v1 firmware at the end of 2026. Users should upgrade to v2.0.0 or later, which requires v2 firmware (spanos2/r202603/05 or later) and a panel passphrase.

Installation

pip install span-panel-api

Dependencies

• httpx — v2 authentication and detection endpoints
• paho-mqtt — MQTT/Homie transport (real-time push)
• pyyaml — YAML parsing for configuration and API payloads

Architecture

Transport

The SpanMqttClient connects to the panel's MQTT broker (MQTTS or WebSocket) and subscribes to the Homie device tree. A two-layer architecture separates generic Homie v5 protocol handling from SPAN-specific interpretation:

• HomiePropertyAccumulator — handles message routing, property and $target storage, dirty-node tracking, and an explicit lifecycle state machine (HomieLifecycle). Protocol-only; no SPAN domain knowledge.
• HomieDeviceConsumer — reads from the accumulator via a query API and builds typed SpanPanelSnapshot dataclasses. Handles power sign normalization, DSM derivation, unmapped tab synthesis, and dirty-node-aware snapshot caching.

Changes are pushed to consumers via callbacks. Dirty-node tracking allows the snapshot builder to skip unchanged nodes, reducing per-scan CPU cost on constrained hardware.

Event-Loop-Driven I/O (Home Assistant Compatible)

The MQTT transport is designed around the Home Assistant core async pattern — all paho-mqtt I/O runs on the asyncio event loop with no background threads:

• NullLock replacement — paho-mqtt's seven internal threading locks are replaced with no-op NullLock instances at setup time, eliminating lock contention since all access is single-threaded on the event loop.
• add_reader / add_writer — AsyncMqttBridge registers the MQTT socket with the event loop via loop.add_reader() and loop.add_writer(), calling paho's loop_read() / loop_write() directly from I/O callbacks rather than from a loop_start() background thread.
• Periodic misc — A loop.call_at() timer fires every second to call loop_misc() for keepalive and timeout housekeeping.
• Executor bridge for connect — The initial TLS handshake and TCP connect are blocking operations, so they run in loop.run_in_executor(). Once the executor returns, socket callbacks are immediately switched from sync bridges (call_soon_threadsafe) back to the async-only versions.

This means the library can be dropped into any asyncio application — including Home Assistant — without spawning threads or requiring thread-safe wrappers.

Circuit Name Synchronization

Circuit names arrive as MQTT retained messages that may land after the Homie device transitions to $state=ready. The client handles this with a bounded wait during connect():

1. After the device reaches ready state, the client polls HomieDeviceConsumer.circuit_nodes_missing_names() every 250ms.
2. As retained name properties arrive, the consumer stores them. Once all circuit-type nodes have a name, the wait returns immediately.
3. If names have not all arrived within 10 seconds, the timeout expires (non-fatal) and the client proceeds — circuits without names will use fallback identifiers.

This ensures that the first get_snapshot() after connect returns human-readable circuit names in the common case, while never blocking indefinitely on a missing retained message.

Protocols

The library defines three structural subtyping protocols (PEP 544) that both the MQTT transport and the simulation engine implement:

Protocol	Purpose
SpanPanelClientProtocol	Core lifecycle: connect, close, ping, get_snapshot
CircuitControlProtocol	Relay and shed-priority control: set_circuit_relay, set_circuit_priority
PanelControlProtocol	Panel-level control: set_dominant_power_source
StreamingCapableProtocol	Push-based updates: register_snapshot_callback, start_streaming, stop_streaming

Integration code programs against these protocols, not transport-specific classes.

Snapshots

All panel state is represented as immutable, frozen dataclasses:

Dataclass	Content
SpanPanelSnapshot	Complete panel state: power, energy, grid/DSM state, hardware status, per-leg voltages, power flows, lugs current, circuits, battery, PV, EVSE
SpanCircuitSnapshot	Per-circuit: power, energy, relay state, priority, tabs, device type, breaker rating, current, $target pending state
SpanBatterySnapshot	BESS: SoC percentage, SoE kWh, vendor/product metadata, nameplate capacity
SpanPVSnapshot	PV inverter: vendor/product metadata, nameplate capacity
SpanEvseSnapshot	EVSE (EV charger): status, lock state, advertised current, vendor/product/serial/version metadata

Usage

Factory Pattern (Recommended)

The create_span_client() factory handles v2 registration and returns a configured SpanMqttClient:

import asyncio
from span_panel_api import create_span_client

async def main():
    client = await create_span_client(
        host="192.168.1.100",
        passphrase="your-panel-passphrase",
    )

    try:
        await client.connect()

        # Get a point-in-time snapshot
        snapshot = await client.get_snapshot()
        print(f"Grid power: {snapshot.instant_grid_power_w}W")
        print(f"Firmware: {snapshot.firmware_version}")
        print(f"Circuits: {len(snapshot.circuits)}")

        for cid, circuit in snapshot.circuits.items():
            print(f"  {circuit.name}: {circuit.instant_power_w}W ({circuit.relay_state})")

    finally:
        await client.close()

asyncio.run(main())

Streaming Pattern

For real-time push updates without polling:

import asyncio
from span_panel_api import create_span_client, SpanPanelSnapshot

async def on_snapshot(snapshot: SpanPanelSnapshot) -> None:
    print(f"Grid: {snapshot.instant_grid_power_w}W, Circuits: {len(snapshot.circuits)}")

async def main():
    client = await create_span_client(
        host="192.168.1.100",
        passphrase="your-panel-passphrase",
    )

    try:
        await client.connect()

        # Register callback and start streaming
        unsubscribe = client.register_snapshot_callback(on_snapshot)
        await client.start_streaming()

        # Run until interrupted
        await asyncio.Event().wait()

    finally:
        await client.stop_streaming()
        await client.close()

asyncio.run(main())

Pre-Built Config Pattern

If you already have MQTT broker credentials (e.g., stored from a previous registration):

from span_panel_api import create_span_client, MqttClientConfig

config = MqttClientConfig(
    broker_host="192.168.1.100",
    username="stored-username",
    password="stored-password",
    mqtts_port=8883,
    ws_port=9001,
    wss_port=443,
)

client = await create_span_client(
    host="192.168.1.100",
    mqtt_config=config,
    serial_number="nj-2316-XXXX",
)

Direct Client Construction

Consumers that manage their own registration and broker configuration can instantiate SpanMqttClient directly:

from span_panel_api import SpanMqttClient, MqttClientConfig

config = MqttClientConfig(
    broker_host="192.168.1.100",
    username="stored-username",
    password="stored-password",
    mqtts_port=8883,
    ws_port=9001,
    wss_port=443,
)

client = SpanMqttClient(
    host="192.168.1.100",
    serial_number="nj-2316-XXXX",
    broker_config=config,
    snapshot_interval=1.0,
)
await client.connect()

Scan Frequency

set_snapshot_interval() controls how often push-mode snapshot callbacks fire. Lower values mean lower latency; higher values reduce CPU usage on constrained hardware. Dirty-node caching (v2.5.0) further reduces per-scan cost by skipping unchanged nodes.

# Reduce snapshot frequency to every 2 seconds
client.set_snapshot_interval(2.0)

Circuit Control

# Set circuit relay (OPEN/CLOSED)
await client.set_circuit_relay("circuit-uuid", "OPEN")
await client.set_circuit_relay("circuit-uuid", "CLOSED")

# Set circuit shed priority (NEVER / SOC_THRESHOLD / OFF_GRID)
await client.set_circuit_priority("circuit-uuid", "NEVER")

Pending-State Detection

When the panel publishes Homie $target properties, SpanCircuitSnapshot exposes the desired state alongside the actual state:

for cid, circuit in snapshot.circuits.items():
    if circuit.relay_state_target and circuit.relay_state_target != circuit.relay_state:
        print(f"  {circuit.name}: relay transitioning {circuit.relay_state} → {circuit.relay_state_target}")
    if circuit.priority_target and circuit.priority_target != circuit.priority:
        print(f"  {circuit.name}: priority pending {circuit.priority} → {circuit.priority_target}")

API Version Detection

Detect whether a panel supports v2 (unauthenticated probe):

from span_panel_api import detect_api_version

result = await detect_api_version("192.168.1.100")
print(f"API version: {result.api_version}")  # "v1" or "v2"
if result.status_info:
    print(f"Serial: {result.status_info.serial_number}")
    print(f"Firmware: {result.status_info.firmware_version}")

v2 Authentication Functions

Standalone async functions for v2-specific HTTP operations:

from span_panel_api import (
    register_v2, download_ca_cert, get_homie_schema,
    regenerate_passphrase, get_v2_status,
    register_fqdn, get_fqdn, delete_fqdn,
)

# Register and obtain MQTT broker credentials
auth = await register_v2("192.168.1.100", "my-app", passphrase="panel-passphrase")
print(f"Broker: {auth.ebus_broker_host}:{auth.ebus_broker_mqtts_port}")
print(f"Serial: {auth.serial_number}")

# Download the panel's CA certificate (for TLS verification)
pem = await download_ca_cert("192.168.1.100")

# Fetch the Homie property schema (unauthenticated)
schema = await get_homie_schema("192.168.1.100")
print(f"Panel size: {schema.panel_size} spaces")
print(f"Schema hash: {schema.types_schema_hash}")

# Rotate MQTT broker password (invalidates previous password)
new_password = await regenerate_passphrase("192.168.1.100", token=auth.access_token)

# Get panel status (unauthenticated)
status = await get_v2_status("192.168.1.100")
print(f"Serial: {status.serial_number}, Firmware: {status.firmware_version}")

# FQDN management (for panel TLS certificate SAN)
await register_fqdn("192.168.1.100", "panel.local", token=auth.access_token)
fqdn = await get_fqdn("192.168.1.100", token=auth.access_token)
await delete_fqdn("192.168.1.100", token=auth.access_token)

Error Handling

All exceptions inherit from SpanPanelError:

Exception	Cause
SpanPanelAuthError	Invalid passphrase, expired token, or missing credentials
SpanPanelConnectionError	Cannot reach the panel (network/DNS)
SpanPanelTimeoutError	Request or connection timed out
SpanPanelValidationError	Data validation failure
SpanPanelAPIError	Unexpected HTTP response from v2 endpoints
SpanPanelServerError	Panel returned HTTP 500

from span_panel_api import SpanPanelAuthError, SpanPanelConnectionError

try:
    client = await create_span_client(host="192.168.1.100", passphrase="wrong")
except SpanPanelAuthError:
    print("Invalid passphrase")
except SpanPanelConnectionError:
    print("Cannot reach panel")

Capabilities

The PanelCapability flag enum advertises transport features at runtime:

Flag	Meaning
EBUS_MQTT	Connected via MQTT/Homie transport
PUSH_STREAMING	Supports real-time push callbacks
CIRCUIT_CONTROL	Can set relay state and shed priority
BATTERY_SOE	Battery state-of-energy available

Project Structure

src/span_panel_api/
├── __init__.py          # Public API exports
├── auth.py              # v2 HTTP provisioning (register, cert, schema, passphrase)
├── const.py             # Panel state constants (DSM, relay)
├── detection.py         # detect_api_version() → DetectionResult
├── exceptions.py        # Exception hierarchy
├── factory.py           # create_span_client() → SpanMqttClient
├── models.py            # Snapshot dataclasses (panel, circuit, battery, PV)
├── phase_validation.py  # Electrical phase utilities
├── protocol.py          # PEP 544 protocols + PanelCapability flags
└── mqtt/
    ├── __init__.py
    ├── accumulator.py   # HomiePropertyAccumulator (Homie v5 protocol layer)
    ├── async_client.py  # NullLock + AsyncMQTTClient (HA core pattern)
    ├── client.py        # SpanMqttClient (all three protocols)
    ├── connection.py    # AsyncMqttBridge (event-loop-driven, no threads)
    ├── const.py         # MQTT/Homie constants + UUID helpers
    ├── homie.py         # HomieDeviceConsumer (SPAN snapshot builder)
    └── models.py        # MqttClientConfig, MqttTransport

Development

See DEVELOPMENT.md for setup, testing, and contribution guidelines.

License

MIT License - see LICENSE file for details.