> ## Documentation Index
> Fetch the complete documentation index at: https://instro.nominal.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Quickstart

> Drive a simulated power supply end-to-end in about five minutes. No hardware required

`instro` ships with a built-in SCPI simulator, so you can try the full library without owning any hardware. This page walks through installing `instro`, launching the simulator, driving it from Python, and reading a measurement back.

<Steps>
  <Step title="Install instro">
    The base install is enough for everything in this quickstart. Optional extras like `[daq]` pull in vendor-specific dependencies. Install those later when you need them (see [Installation](/instrumentation/installation)).

    ```bash theme={null}
    pip install instro
    ```
  </Step>

  <Step title="Start the simulated PSU">
    Open a separate terminal and start the bundled simulator. It listens on `127.0.0.1:5025` and stays running until you press <kbd>Ctrl</kbd>+<kbd>C</kbd>.

    ```bash theme={null}
    python -m instro.psu.scpi_sim_server
    ```

    Leave it running in the background while you work through the rest of the steps.
  </Step>

  <Step title="Construct an InstroPSU">
    In a new Python session or script, create an `InstroPSU` backed by the `SimulatedPSU` driver. The driver owns the VISA transport. You pass it the simulator's socket resource string, and `InstroPSU` handles everything else.

    ```python theme={null}
    from instro.psu import InstroPSU
    from instro.psu.drivers import SimulatedPSU

    psu = InstroPSU(
        name="bench_psu",
        driver=SimulatedPSU("TCPIP0::127.0.0.1::5025::SOCKET"),
        num_channels=2,
    )
    psu.open()
    ```

    <Tip>
      `InstroPSU` is the category-level interface. `SimulatedPSU` is one of several drivers. Swap in `BK9115`, `KeysightE36100`, `RigolDP800`, `SiglentSPD3303`, or `TDKLambdaGenesys` to talk to real hardware without changing the rest of your code.
    </Tip>
  </Step>

  <Step title="Set a voltage and enable the output">
    Configure channel 1 with a 5 V setpoint, a 1 A current limit, and overvoltage protection at 5.5 V, then enable the output.

    ```python theme={null}
    psu.set_voltage(5.0, channel=1)
    psu.set_current_limit(1.0, channel=1)
    psu.set_overvoltage_protection_level(5.5, channel=1)
    psu.set_overvoltage_protection_enabled(True, channel=1)
    psu.output_enable(True, channel=1)
    ```

    The simulator models protection trips just like a real supply: if the output ever exceeds the OVP threshold, the channel shuts down and `SYST:ERR?` reports the trip.
  </Step>

  <Step title="Read a measurement back">
    Measurement getters return a `Measurement` object. Use `.latest` to grab the current value. Every measurement is timestamped and tagged automatically, ready to stream to a [Publisher](/instrumentation/publishers).

    ```python theme={null}
    voltage = psu.get_voltage(channel=1)
    current = psu.get_current(channel=1)
    print(f"V: {voltage.latest:.3f} V")
    print(f"I: {current.latest:.3f} A")
    ```

    When you're done, disable the output and close the connection. Turning the output off before disconnecting is standard bench safety, and `close()` does more than drop the socket: it stops the background daemon and flushes any attached publishers.

    ```python theme={null}
    psu.output_enable(False, channel=1)
    psu.close()
    ```
  </Step>
</Steps>

That's the whole loop: construct → `open()` → configure → measure → `close()`. Every instrument category in `instro` follows the same shape.

## Two ways to manage the lifecycle

You can drive the instrument with explicit `open()` / `close()` calls, or let Python do it for you with a `with` block. Both are first-class. Pick whichever fits your script. Every `instro` instrument is a context manager. `__enter__` calls `self.open()`, `__exit__` calls `self.close()` (including when an exception escapes the block, so the daemon and publishers always get torn down). This works for every built-in category (`InstroPSU`, `InstroDMM`, `InstroDAQ`, `InstroELoad`, `I2CInterface`, …) and for any custom `Instrument` subclass (see [Custom instruments](/instrumentation/custom-instruments)).

<Tabs>
  <Tab title="Explicit open() / close()">
    Best when the instrument's lifetime spans many functions, or when you want to interleave setup and teardown across event handlers, fixtures, or REPL sessions.

    ```python theme={null}
    from instro.psu import InstroPSU
    from instro.psu.drivers import SimulatedPSU

    psu = InstroPSU(
        name="bench_psu",
        driver=SimulatedPSU("TCPIP0::127.0.0.1::5025::SOCKET"),
        num_channels=2,
    )
    psu.open()

    psu.set_voltage(5.0, channel=1)
    psu.set_current_limit(1.0, channel=1)
    psu.output_enable(True, channel=1)

    voltage = psu.get_voltage(channel=1)
    print(f"V: {voltage.latest:.3f} V")

    psu.output_enable(False, channel=1)
    psu.close()
    ```
  </Tab>

  <Tab title="with block">
    Best for scripts and tests where the instrument is used inside a single scope. `close()` runs automatically on the way out, even if an exception is raised.

    ```python theme={null}
    from instro.psu import InstroPSU
    from instro.psu.drivers import SimulatedPSU

    with InstroPSU(
        name="bench_psu",
        driver=SimulatedPSU("TCPIP0::127.0.0.1::5025::SOCKET"),
        num_channels=2,
    ) as psu:
        psu.set_voltage(5.0, channel=1)
        psu.set_current_limit(1.0, channel=1)
        psu.output_enable(True, channel=1)

        voltage = psu.get_voltage(channel=1)
        print(f"V: {voltage.latest:.3f} V")
    ```
  </Tab>
</Tabs>

## Where to next

<Columns cols={2}>
  <Card title="Library overview" icon="compass" href="/instrumentation/overview">
    How instruments, drivers, publishers, and the background daemon fit together.
  </Card>

  <Card title="Power supplies in depth" icon="bolt" href="/instrumentation/psu">
    Multi-channel use, supported vendors, custom driver development, and the background telemetry daemon.
  </Card>

  <Card title="Stream to Nominal Core" icon="rocket" href="/instrumentation/publishers">
    Attach a publisher in one line to ship measurements live to Nominal Core, Connect, or a file.
  </Card>

  <Card title="Examples gallery" icon="file-code" href="/instrumentation/examples">
    Runnable end-to-end scripts for every supported instrument category.
  </Card>
</Columns>