Configuring Stations #

This guide covers station configuration for different environments.

Basic Station Config #

# stations/bench_1.yaml
id: bench_1
name: "Production Bench 1"
location: "Lab A"
 
instruments:
  dmm:
    type: dmm
    driver: pymeasure.instruments.keysight.Keysight34461A
    resource: "TCPIP::192.168.1.100::INSTR"
  psu:
    type: psu
    driver: pymeasure.instruments.keysight.KeysightE36312A
    resource: "GPIB0::5::INSTR"

Station Fields #

Field	Required	Description
`id`	Yes	Unique identifier
`name`	No	Display name
`location`	No	Physical location
`description`	No	Description
`supported_phases`	No	Which test phases this station supports

Instrument Fields #

Per StationInstrumentConfig in src/litmus/models/station.py:

Field	Required	Description
`type`	Yes	Instrument type (dmm, psu, etc.)
`driver`	At least one of driver/resource (unless `mock: true`)	Dotted import path to the driver class (e.g. `pymeasure.instruments.keysight.Keysight34461A`)
`resource`	At least one of driver/resource (unless `mock: true`)	VISA address or connection string
`catalog_ref`	No	ID of a catalog entry that declares this instrument's capabilities
`channels`	No	Dict of named channel→port mappings
`description`	No	Human-readable description
`mock`	No	Always mock this instrument (even without `--mock-instruments`). Default `false`
`mock_config`	No	Return values when running in mock mode

VISA Addresses #

TCP/IP (LAN) #

resource: "TCPIP::192.168.1.100::INSTR"
resource: "TCPIP::192.168.1.100::5025::SOCKET"  # With port
resource: "TCPIP::dmm.lab.local::INSTR"  # DNS name

GPIB #

resource: "GPIB0::5::INSTR"   # Board 0, address 5
resource: "GPIB1::12::INSTR"  # Board 1, address 12

USB #

resource: "USB0::0x2A8D::0x0101::MY12345::INSTR"
# Format: USB{board}::{vendor}::{product}::{serial}::INSTR

Serial #

resource: "ASRL/dev/ttyUSB0::INSTR"  # Linux
resource: "ASRLCOM3::INSTR"          # Windows

Mock Mode Configuration #

Configure default values for --mock-instruments mode:

instruments:
  dmm:
    type: dmm
    driver: pymeasure.instruments.keysight.Keysight34461A
    resource: "TCPIP::192.168.1.100::INSTR"
    mock_config:
      measure_dc_voltage: 3.31
      measure_current: 0.1
      measure_resistance: 1000

Running in Mock Mode #

pytest tests/ --station=stations/bench_1.yaml --mock-instruments --dut-serial=SIM001

The --mock-instruments flag uses mock instruments instead of real hardware. Mock values come from mock_config in the station, or can be overridden per-test in the sidecar YAML next to your test file (tests/test_*.yaml).

Station Types #

A station type is a template — one YAML file per type under stations/types/<id>.yaml. It declares the instrument roles (and their type:) every station of that type must provide, plus the catalog capability ids the type advertises:

# stations/types/voltage_tester.yaml
id: voltage_tester
description: "Basic voltage testing station"
instruments:
  dmm:
    type: dmm
  psu:
    type: psu
capabilities:
  - keysight.34461a.dc_voltage
  - keysight.e36312a.dc_source

# stations/types/full_test.yaml
id: full_test
description: "Complete test station"
instruments:
  dmm:
    type: dmm
  psu:
    type: psu
  scope:
    type: scope

There is no required: field on an instrument entry — every role listed under instruments: is required, and any role not listed is omitted by definition. capabilities: is a list of catalog capability ids (strings), not inline Capability dicts.

Reference in station instances:

# stations/bench_1.yaml
id: bench_1
station_type: voltage_tester
location: "Lab A"
 
instruments:
  dmm:
    type: dmm
    driver: pymeasure.instruments.keysight.Keysight34461A
    resource: "TCPIP::192.168.1.100::INSTR"
  psu:
    type: psu
    driver: pymeasure.instruments.keysight.KeysightE36312A
    resource: "GPIB0::5::INSTR"

Multiple Stations #

Production Lab #

# stations/prod_bench_1.yaml
id: prod_bench_1
name: "Production Bench 1"
location: "Production Floor, Bay 1"
 
supported_phases:
  - production
 
instruments:
  dmm:
    type: dmm
    driver: pymeasure.instruments.keysight.Keysight34461A
    resource: "TCPIP::192.168.10.101::INSTR"
  psu:
    type: psu
    driver: pymeasure.instruments.keysight.KeysightE36312A
    resource: "TCPIP::192.168.10.102::INSTR"

Development Lab #

# stations/dev_bench.yaml
id: dev_bench
name: "Development Bench"
location: "R&D Lab"
 
supported_phases:
  - development
  - debug
 
instruments:
  dmm:
    type: dmm
    driver: pymeasure.instruments.keysight.Keysight34461A
    resource: "USB0::0x2A8D::0x0101::MY12345::INSTR"
  psu:
    type: psu
    driver: pymeasure.instruments.keysight.KeysightE36312A
    resource: "GPIB0::5::INSTR"
  scope:
    type: scope
    driver: drivers.scope.MyScope
    resource: "TCPIP::192.168.1.200::INSTR"

CI/CD #

# stations/ci_station.yaml
id: ci_station
name: "CI Environment"
description: "For automated testing with --mock-instruments"
 
instruments:
  dmm:
    type: dmm
    mock: true
    catalog_ref: generic_dmm
    mock_config:
      measure_dc_voltage: 3.31
      measure_current: 0.1
  psu:
    type: psu
    mock: true
    catalog_ref: generic_psu
    mock_config:
      measure_voltage: 5.0

Run in CI:

pytest tests/ --station=stations/ci_station.yaml --mock-instruments --dut-serial=CI-TEST

Selecting a fixture at run time #

Stations don't pin a fixture themselves. The active fixture is selected by --fixture=... on the pytest command line (or by a profile that sets it). The plugin validates that the fixture's product_id / product_family matches the active product spec before any test runs.

pytest tests/ \
  --station=bench_1 \
  --fixture=fixtures/power_board_fixture.yaml \
  --dut-serial=SN001

See Fixtures for the pin-to-instrument mapping model.

Capability Declarations #

A station instance (stations/<id>.yaml) does not carry a capabilities: field — capabilities are derived from each instrument's catalog entry at load time (the matcher walks station.instruments → instrument.catalog_ref → catalog/<...>.yaml → capabilities[]).

If you want to advertise a fixed capability set as part of a type (so concrete stations of that type are guaranteed to provide it), declare it on the station type, not on the instance, as a list of catalog capability ids:

# stations/types/voltage_bench.yaml
id: voltage_bench
description: "Generic DC + AC voltage bench"
instruments:
  dmm: {type: dmm}
  psu: {type: psu}
capabilities:
  - keysight.34461a.dc_voltage
  - keysight.34461a.ac_voltage
  - keysight.e36312a.dc_source

To customize the capabilities a specific instrument provides, edit that instrument's catalog YAML (catalog/<vendor>/<model>.yaml) — not the station file.

Validation #

Station configuration is validated by Pydantic models when loaded:

from litmus.store import load_station
 
# Raises pydantic.ValidationError if config is invalid
station = load_station("stations/bench_1.yaml")
print(f"Station: {station.id}")
print(f"Instruments: {list(station.instruments.keys())}")

Invalid configurations raise pydantic.ValidationError with details about what's wrong.

Shared Instruments (Multi-DUT) #

When a fixture defines multiple slots (parallel DUT positions — see Multi-DUT testing), instruments referenced by more than one slot are automatically detected as shared. The orchestrator connects shared instruments once and hosts them via an internal RPC server (InstrumentServer in src/litmus/instruments/server.py); worker subprocesses access them through transparent proxy objects. Tests never know the difference.

Per-Resource Locking #

Locking is keyed on the instrument's resource string (e.g., VISA address), not the role name:

Same resource → same driver session → same lock → serialized access
Different resources → different sessions → independent locks → parallel access
Switches → concurrent access (relay operations are atomic)

Two roles pointing at the same physical instrument share a lock automatically:

instruments:
  dmm:
    type: dmm
    resource: "TCPIP::192.168.1.100::INSTR"   # ← lock key
  scope:
    type: scope
    resource: "TCPIP::192.168.1.100::INSTR"   # ← same resource = same lock

Automatic Server Setup #

No special flags are needed. When the fixture defines multiple slots that share an instrument role, the orchestrator automatically:

Connects the shared instruments once in the orchestrator process
Starts an internal RPC server to serve them
Worker subprocesses get transparent RemoteInstrumentProxy objects

instruments:
  dmm:
    type: dmm
    driver: pymeasure.instruments.keysight.Keysight34461A
    resource: "TCPIP::192.168.1.100::INSTR"
  matrix:
    type: switch
    driver: drivers.switch.RelayMatrix
    resource: "TCPIP::192.168.1.106::INSTR"

Best Practices #

Use descriptive IDs — prod_bench_1 not station1
Include location — Helps operators find equipment
Define supported phases — Prevents wrong usage
Use environment variables — For IP addresses in different environments
Create CI station — Fully simulated for automated tests
Version control — Track station changes

Common Configurations #

Single DMM #

id: simple_station
 
instruments:
  dmm:
    type: dmm
    driver: pymeasure.instruments.keysight.Keysight34461A
    resource: "USB0::0x2A8D::0x0101::MY12345::INSTR"

Full Production #

id: production_station
location: "Production Floor"
 
instruments:
  dmm_1:
    type: dmm
    driver: pymeasure.instruments.keysight.Keysight34461A
    resource: "TCPIP::192.168.1.101::INSTR"
  dmm_2:
    type: dmm
    driver: pymeasure.instruments.keysight.Keysight34461A
    resource: "TCPIP::192.168.1.102::INSTR"
  psu:
    type: psu
    driver: pymeasure.instruments.keysight.KeysightE36312A
    resource: "TCPIP::192.168.1.103::INSTR"
  eload:
    type: eload
    driver: drivers.eload.MyELoad
    resource: "TCPIP::192.168.1.104::INSTR"
  scope:
    type: scope
    driver: drivers.scope.MyScope
    resource: "TCPIP::192.168.1.105::INSTR"

Next Steps #

Stations Concept — Understanding stations
Capabilities — Capability matching
Custom drivers — Build a non-VISA driver