Spvirit

Spvirit is a pure-Rust implementation of the EPICS PVAccess protocol — client, server, wire codec, command-line tools, and Python bindings — with no dependency on an EPICS base installation.

Quickstart

Install. This one command brings the Python module and the twelve sp* command-line tools; there is no compiler and no Rust toolchain involved on Linux, macOS, or Windows x86_64.

pip install spvirit

Save this as first.py — it is a complete soft IOC serving three PVs:

temp = spvirit.ai("SIM:TEMPERATURE", 22.5)      # input  — read-only to clients
setpoint = spvirit.ao("SIM:SETPOINT", 25.0)     # output — clients may write
enable = spvirit.bo("SIM:ENABLE", False)        # output — a writable bool

server = spvirit.Server(pvs=[temp, setpoint, enable])
server.run()

Run it, and read a PV from a second terminal:

python first.py            # terminal 1 — it blocks, serving

$ spget SIM:TEMPERATURE
SIM:TEMPERATURE 2026-08-06 09:38:00.729 22.5

$ spput SIM:SETPOINT 30
SIM:SETPOINT OK

$ spget SIM:SETPOINT
SIM:SETPOINT 2026-08-06 09:38:00.729  30

If you see those three lines you have a working PVAccess server. Nobody configured a port, an address, or a permission: the client broadcast the PV name, the server answered, and SIM:TEMPERATURE refused the write it should refuse because ai is an input record.

The same thing in Rust is Your first PV; every chapter of this book shows both languages.

Where to go next

• Never met EPICS? → EPICS in 10 minutes
• Know EPICS, want a soft IOC? → Your first PV
• Want the whole tour? → Serving scalars and the twelve chapters after it
• Looking up a function? → API reference below

How the site is laid out

• Fundamentals — what EPICS is, what Normative Types are, and the one distinction worth understanding before you write anything: records vs raw NT.
• Getting started — install, then a PV served and read in under a page.
• Progressive examples — thirteen chapters, Rust and Python side by side, ending in a complete IOC.
• Command-line tools — a page per sp* binary, with real captured output.
• Reference — the crate map, the record-type matrix, the Python API, troubleshooting, and the known gaps.
• Developer guide — internals, with file-and-line citations, for people changing spvirit itself.

API reference

This book is the tutorial. The exhaustive, generated API documentation lives on docs.rs, one page per crate:

For Python there is no generated site; the Python API chapter is the reference, and every object carries a docstring, so help(spvirit.ai) works at the prompt.

Project

• Licence — BSD-3-Clause. See Licence and support.
• Source and issues — github.com/ISISNeutronMuon/spvirit
• Contributing — Licence and support has the short version; the Developer guide has the long one.

Every code sample on this site is included verbatim from a file in the repository that is compiled by CI. The badge at the top of each chapter links to that source and to the test that checks it — including the quickstart above:

✅ Verified · demo_first_pv.py · check docs_verify ·

The badge reports the whole docs-verify suite, not this chapter alone.