sila2

tested on simulator

Tier	Tier 2
Protocol	SiLA 2 over gRPC
Covers	SiLA 2 lab devices, SiLA 2 gateways, custom SiLA 2 servers
Hazard default	medium
Conformance	full
Tested with	a thermoshaker served by the sila2 package's own server from feature definitions

Estimated reach. Dozens of commercial device families and any custom SiLA 2 server. SiLA 2 is the lab automation standard from the SiLA consortium. Several vendors ship SiLA 2 servers for their instruments, and integrators wrap older instruments with SiLA 2 gateways. The driver reads any feature's properties and runs its commands without generated code, so coverage follows the feature definitions a server offers. The count is a model estimate.

The sila2 driver connects to SiLA 2 lab automation devices with the sila2 package 0.14.0, loading features from the server's Feature Definitions. Properties become reads or streams, and commands become actions and channel changes. describe drafts a file from the definitions.

Supports

Every channel and action names a SiLA feature in a map.

Map	Meaning
{ feature: TemperatureController, property: CurrentTemperature }	A property. Observable properties stream
{ feature: TemperatureController, property: DeviceState, field: LidClosed }	One element of a structure property
{ feature: TemperatureController, command: SetTargetTemperature, parameter: TargetTemperature, readback: TargetTemperature }	A channel that changes through a command and reads back from a property
{ feature: ShakeController, command: Shake, parameters: { rpm: Speed, seconds: Duration } }	An action, each argument naming a parameter
{ ..., base: { Mode: Gentle } }	Fixed values for the command's other parameters

feature is the identifier, or the fully qualified form such as org.example/lab/TemperatureController/v1 to pin a version. unit overrides the Unit constraint and scale multiplies the value.

How the protocol is handled

• Connect checks every named feature, property, command, parameter, type and unit, and allows 8 s for feature compilation.
• Observable properties stream from connect, and others read on demand.
• A channel changes through a one-parameter command and reads back the last value sent without readback.
• An observable command returns done within action_wait, or started.
• Execution errors fail the command with identifier and message, such as TooHot, and constraint violations return validation errors.
• sila2 0.14 loads two builds of the framework protos, which conflict once another package such as aioesphomeapi loads protobuf. The driver registers one build under both names, so SiLA runs beside every other driver.

Safe state

SiLA has no general stop, so give the file a safe_state with the device's own stop commands and safe setpoints.

Discovery

openhal discover lists _sila._tcp.local. mDNS services heard within 2 s.

Setup

1. Install with uv tool install --compile-bytecode "halkit[sila2] @ git+https://github.com/sohan-bhat/OpenHAL".
2. Save the server's CA certificate as a PEM file, since SiLA servers encrypt by default, often with a self-signed CA in the mDNS record.
3. Start from openhal/drivers/sila2/examples/thermoshaker.hal.yaml or describe.

Key	Default	Meaning
host	required	Server host
port	50052	Server port
insecure	false	No encryption, for development servers only
ca_env	none	Variable holding the CA certificate PEM path
timeout	5 s	Per call
action_wait	8 s	Time before an observable command returns started, at most 9 s

Known limitations

• No lists, binaries, dates, times or nested structures in parameters yet.
• Running observable commands can't be cancelled. Use the device's own stop command.
• No SiLA metadata such as LockController lock identifiers.

Hazard defaults

medium, since lab devices heat, spin and move plates. Use high for devices that can injure, such as centrifuges and robotic arms.

Sources

• SiLA 2 Part A, overview and concepts, and Part B, mapping to gRPC, https://sila-standard.com/standards/
• SiLA feature definition schema and core features, https://gitlab.com/SiLA2/sila_base
• sila2 Python package documentation, https://sila2.gitlab.io/sila_python/