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mcpyvisa

Simulated Bench

This tutorial gets you from zero to a working mcpyvisa session using simulated instruments. No GPIB adapters, no physical test equipment, no proprietary VISA drivers. By the end, you will have queried a virtual multimeter, set a voltage on a virtual power supply, and seen exactly what a real session looks like — all backed by YAML definitions that respond like the real hardware.

What you will need

Section titled “What you will need”
  • Python 3.11+ with uv installed
  • Claude Code (or another MCP-compatible client)

That is it. No instruments, no adapters, no cables.

Install mcpyvisa with sim support

Section titled “Install mcpyvisa with sim support”

  1. Install with the sim extra

    The sim backend depends on pyvisa-sim, which is included in the sim optional dependency group:

    Terminal window
    uv add mcpyvisa[sim]

  2. Get the instrument definitions

    The GPIB Instrument Catalog provides all_instruments.yaml — a pyvisa-sim definition file containing 16 simulated instruments covering multimeters, power supplies, oscilloscopes, signal generators, and more.

    Clone the catalog (or just grab the YAML file):

    Terminal window
    git clone https://git.supported.systems/warehack.ing/mcgpib.git

    The file lives at mcgpib/gpib-catalog/sim/all_instruments.yaml.

  3. Create your configuration

    Create mcpyvisa.toml in your working directory (or at ~/.config/mcpyvisa/config.toml):

    mcpyvisa.toml
    [server]
    log_level = "INFO"
    

    [[backend]]
    name = "sim-bench"
    type = "sim"
    sim_file = "./gpib-catalog/sim/all_instruments.yaml"
    

    # Give a few instruments friendly names
    [instruments.dmm]
    resource = "GPIB0::22::INSTR"
    backend = "sim-bench"
    

    [instruments.psu]
    resource = "GPIB0::5::INSTR"
    backend = "sim-bench"
    

    [instruments.counter]
    resource = "GPIB0::3::INSTR"
    backend = "sim-bench"

  4. Add to Claude Code

    Terminal window
    claude mcp add mcpyvisa -- uvx mcpyvisa[sim]

Connect and explore

Section titled “Connect and explore”

Start a Claude Code session and try the following.

  1. Connect to the sim backend

    > Connect to my backend "sim-bench"

    Claude calls connect_backend("sim-bench"). The server creates a pyvisa ResourceManager pointing at your YAML definition file and discovers all 16 simulated instruments:

    Connected to sim-bench (sim)
    Discovered 16 instrument(s):
      GPIB0::1::INSTR  — FLUKE,8842A
      GPIB0::2::INSTR  — TEKTRONIX,TDS 2024B
      GPIB0::3::INSTR  — HEWLETT-PACKARD,53131A (alias: counter)
      GPIB0::5::INSTR  — HEWLETT-PACKARD,E3631A (alias: psu)
      GPIB0::7::INSTR  — HEWLETT-PACKARD,1660A
      GPIB0::9::INSTR  — HEWLETT-PACKARD,3488A
      GPIB0::10::INSTR — HEWLETT-PACKARD,33120A
      GPIB0::16::INSTR — KEITHLEY INSTRUMENTS INC.,MODEL 2000
      GPIB0::17::INSTR — HEWLETT-PACKARD,4284A
      GPIB0::18::INSTR — HEWLETT-PACKARD,8566B
      GPIB0::19::INSTR — HEWLETT-PACKARD,8657B
      GPIB0::22::INSTR — HEWLETT-PACKARD,34401A (alias: dmm)
      GPIB0::23::INSTR — HEWLETT-PACKARD,3458A
      GPIB0::24::INSTR — HEWLETT-PACKARD,3478A
      GPIB0::25::INSTR — KEITHLEY INSTRUMENTS INC.,MODEL 2400
      GPIB0::27::INSTR — KEITHLEY INSTRUMENTS INC.,MODEL 6517B

    These are classic bench instruments from HP/Agilent, Keithley, Fluke, and Tektronix. Each one responds to its documented SCPI (or legacy) command set.

  2. Identify an instrument by alias

    > Identify the instrument "dmm"
    dmm (GPIB0::22::INSTR on sim-bench):
      Manufacturer: HEWLETT-PACKARD
      Model: 34401A
      Serial: 0
      Firmware: 0

  3. Query the simulated multimeter

    > What is the DMM reading?

    Claude calls instrument_query("dmm", "MEAS:VOLT:DC?"). The simulated HP 34401A returns a randomized voltage reading:

    +1.23456789E+00

    Each query returns a different value — pyvisa-sim’s RANDOM() function generates plausible readings within the configured range.

  4. Set a voltage on the power supply

    > Set the PSU output to 5 volts on channel P6V

    Claude sends the appropriate SCPI commands:

    instrument_write("psu", "INST:SEL P6V")   → Sent to psu
    instrument_write("psu", "VOLT 5.0")        → Sent to psu
    instrument_write("psu", "OUTP ON")         → Sent to psu

    The simulated E3631A accepts these commands just as the real hardware would. Query back to confirm:

    > Read the voltage setting back
    instrument_query("psu", "VOLT?") → 5.000000E+00

  5. Explore other instruments

    With 16 instruments on the bus, there is plenty to explore:

    > What instruments are on the bus? Identify the signal generator.
    > Read a frequency from the counter
    > What does the Keithley 2400 source-measure unit support?

What is next

Section titled “What is next”