SCPI

SCPI
Name	SCPI
Full name	Standard Commands for Programmable Instruments
Introduced	1990
Developer	IEEE, IEC, Hewlett-Packard
Status	active
Related	IEEE-488, VXI, LXI, USB Test and Measurement Class

SCPI SCPI is a standardized command set used to control programmable test and measurement instruments. It provides a common syntax and semantics for instrument communication across vendors such as Hewlett-Packard, Tektronix, Keysight Technologies, and National Instruments, and interoperates with bus and protocol standards including IEEE-488, VXI, LXI, and USB Test and Measurement Class. SCPI streamlines automation workflows for laboratories and production lines that employ instruments from manufacturers like Agilent Technologies and Rohde & Schwarz.

Overview

SCPI defines a hierarchical, human-readable command language for instruments such as oscilloscopes, signal generators, spectrum analyzers, multimeters, and power supplies produced by companies including Fluke, Anritsu, Brookhaven National Laboratory, and Tektronix. The standard decouples instrument-specific configuration from transport layers like GPIB and Ethernet (IEEE 802.3), enabling control via interfaces facilitated by vendors including National Instruments and software environments like LabVIEW, MATLAB, Python (programming language), and C#. SCPI commands map to instrument functions used in automated test systems developed by organizations such as NASA and CERN.

History and development

SCPI emerged from efforts undertaken in the late 1980s and early 1990s by instrument manufacturers and standards bodies including IEEE and the International Electrotechnical Commission. Early work built on the HP-IB command heritage and the IEEE-488 standard to address proliferation of incompatible vendor command sets at laboratories such as Los Alamos National Laboratory and industrial test sites like those run by General Electric and Siemens. Formal documentation and extensions were published and adopted by vendors including Hewlett-Packard and later Agilent Technologies when it spun off divisions, while subsequent consolidation involved companies such as Keysight Technologies and Tektronix. Over time, SCPI evolved alongside transport standards such as VXIbus and network frameworks like LXI.

Architecture and command language

SCPI uses a tree-like command hierarchy where keywords such as SOURCE, MEASURE, and OUTPUT combine with parameters and queries; examples of keywords appear in instrument manuals from Keysight Technologies and Rohde & Schwarz. The language supports both short and long keyword forms to balance brevity and readability in environments like LabVIEW and Python (programming language), and includes query syntax using the question mark character for interrogating state, as implemented in firmware by vendors including Tektronix and Anritsu. SCPI commands are structured to be stateless where practical and to present consistent behaviors across types such as digital multimeter modules, spectrum analyzer systems, and function generator products. Error reporting follows conventions mirrored in test frameworks developed by institutions such as MIT and Imperial College London to enable robust automated error handling.

Implementations and device support

Major test and measurement manufacturers provide SCPI support in firmware for instruments like oscilloscopes from Tektronix, signal analyzers from Rohde & Schwarz, and multimeters from Fluke. Software toolkits and drivers enabling SCPI transport exist from National Instruments (Measurement & Automation Explorer), Tektronix (TekVISA), and third-party projects integrated into Python (programming language) libraries and LabVIEW drivers used at facilities such as Sandia National Laboratories and Lawrence Berkeley National Laboratory. SCPI is commonly implemented over GPIB (IEEE-488), VXI, LXI (HTTP/TCP), and USB using the USB Test and Measurement Class; manufacturers including Keysight Technologies and Yokogawa provide vendor-specific extensions while maintaining SCPI base compatibility.

Applications and use cases

SCPI is widely used in automated test equipment (ATE) systems for semiconductor verification at companies such as Intel Corporation and Taiwan Semiconductor Manufacturing Company, in aerospace avionics test benches used by organizations like Boeing and Airbus, and in academic research at universities like Stanford University and Caltech for data acquisition and instrument orchestration. Production test, calibration laboratories accredited to standards from bodies like ISO commonly rely on SCPI for repeatable instrument control. SCPI-based scripting and instrument orchestration integrate with test management systems from vendors such as National Instruments and Keysight Technologies and with continuous integration pipelines adopted by engineering teams at IBM and Microsoft for hardware validation.

Extensions and related standards

Beyond the core SCPI command set, vendors and consortia have defined extensions and complementary standards: LXI provides Ethernet-based discovery and control for SCPI-capable instruments, VXI defines modular instrumentation backplanes supporting SCPI command interpretation, and the USB Test and Measurement Class standardizes USB transport. Instrument-specific instruction sets and profiles from Keysight Technologies, Rohde & Schwarz, and Tektronix extend SCPI to cover features in devices like vector signal generators and digitizers, while interoperability efforts reference standards from IEEE and the International Electrotechnical Commission. Open-source projects and community repositories maintained by organizations like GitHub hosts add drivers and parsers that implement SCPI across platforms including Linux, Windows, and macOS.

Category:Instrumentation