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SCPI Instrument Patterns

Reusable patterns for automating bench instruments in post-silicon validation.

Stack layers

Your test (pytest / OpenTAP / script)
        ↓
   PyMeasure (high-level procedures)
        ↓
   PyVISA (transport)
        ↓
   pyvisa-py / NI-VISA / linux-gpib (backend)
        ↓
   Instrument (LXI / GPIB / USB-TMC)

Discovery

# List LXI instruments on the subnet
lxi discover

# PyVISA resource scan
python -c "import pyvisa; print(pyvisa.ResourceManager('@py').list_resources())"

Minimal measurement

import pyvisa

rm = pyvisa.ResourceManager("@py")
inst = rm.open_resource("TCPIP0::192.168.1.100::INSTR")
inst.timeout = 10000
inst.write("*RST")
inst.write(":MEAS:VOLT?")
print(float(inst.read()))
inst.close()

PyMeasure procedure pattern

from pymeasure.instruments.keithley import Keithley2400
from pymeasure.adapters import VISAAdapter

adapter = VISAAdapter("TCPIP0::192.168.1.10::INSTR")
source = Keithley2400(adapter)
source.apply_voltage()
source.source_voltage = 1.8
source.enable_source()
print(source.current)

Best practices for DVT labs

  • Set explicit timeouts on every session
  • Send *CLS;*RST at test start for deterministic state
  • Log raw SCPI transcripts alongside parsed measurements
  • Store calibration due dates in your test-plan metadata (Doorstop / Kiwi TCMS)
  • Use @pytest.mark.hardware for tests that require physical instruments

Common instrument classes

Class Example tools Typical validation use
DMM / Source-meter Keithley 2400, Keysight 34461A Rail current, PMIC efficiency
Scope Keysight DSOX, Tektronix MSO Eye diagram, rise time
Spectrum analyzer Keysight N9000 EMI spot checks
Traffic generator Spirent, pktgen-DPMDK Line-rate packet validation