VISA Codec

The VISA codec is included in the zeloscloud package, and requires extras visa to be installed.

Read these!

Much of the configuration infrastructure for defining messages and signals is shared with serial. Read more here: - serial codec - serial schema

Glossary

VISA stands for Virtual Instrument Software Architecture.

https://en.wikipedia.org/wiki/Virtual_instrument_software_architecture

Standard Commands for Programmable Instruments

https://en.wikipedia.org/wiki/Standard_Commands_for_Programmable_Instruments

Introduction

Many instruments accept SCPI commands over a VISA connection. Common device types include oscilloscopes, power analyzers, grid simulators, battery simulators, and much more.

By issuing commands/queries to VISA/SCPI-compliant third party hardware, users can automate testing, fault injection, data capture, and more.

Quick Start Guide

This section will walk through creating and using a VisaCodec, a VisaLink, and the corresponding Signals/ Messages

Basic Pytest Setup

To set up a basic codec, you need to initialize it with a name, link, and configuration file. Here's a quick example to get you started:

conftest.py

import pytest
import yaml
from zeloscloud.links.visa_link import VisaLink
from zeloscloud.codecs.visa import VisaCodec


@pytest.fixture(scope="session")
def visa_link():
    """Initialize and open a visa link."""
    with VisaLink(name="link", identifier="MY_INSTRUMENT") as link:
        yield link


@pytest.fixture(scope="session")
def visa_config():
    """Load the visa config yaml which defines the cmd/queries."""
    with open("instrument_signals.yml", "r") as f:
        config = yaml.safe_load(f)
    yield config


@pytest.fixture(scope="session")
def visa_codec(visa_link, visa_config):
    """Create a serial codec with and generate all the cmd/query objects."""
    with VisaCodec(name="visa_codec", link=visa_link, config=visa_config) as codec:
        yield codec


def test_visa_link(visa_link, check):
    check.that("MANUFACTURER NAME", "in", visa_link.query("*IDN?"))


def test_visa_codec(visa_codec, check):
    check.that("MANUFACTURER NAME", "in", visa_codec.identity)

Pytest Fixtures

We are utilizing pytest fixtures to inject dependencies into our tests and setups. This method ensures that our components are modular and can be tested independently. The visa_codec and visa_link fixtures can also be used as standalone components.

Default SCPI Commands

By default, the VISA codec includes a common set of signals and message you may use out of the box. The signals and messages are defined by IEEE 488.2 Common Commands. To view more information about these commands/queries, please visit the following page:

https://rfmw.em.keysight.com/spdhelpfiles/truevolt/webhelp/US/Content/__I_SCPI/IEEE-488_Common_Commands.htm

The config file used for generating the signals/messages:

signals:
  # IEEE 488.2 Common Command: *TST (Self-Test)
  self_test:
    query:
      cmd: "*TST?"
      pattern: "(\\d+)"
    data_type: int

  # IEEE 488.2 Common Command: *STB (Read Status Byte)
  status_byte:
    query:
      cmd: "*STB?"
      pattern: "(\\d+)"
    data_type: int

  # IEEE 488.2 Common Command: *OPC (Operation Complete)
  operation_complete:
    query:
      cmd: "*OPC?"
      pattern: "(\\d+)"
    data_type: int

  # IEEE 488.2 Common Command: *ESR (Standard Event Status Register)
  event_status_register:
    query:
      cmd: "*ESR?"
      pattern: "(\\d+)"
    data_type: int

  # IEEE 488.2 Common Command: *SRE (Service Request Enable)
  service_request_enable:
    cmd: "*SRE {}"
    query:
      cmd: "*SRE?"
      pattern: "(\\d+)"
    data_type: int

  # IEEE 488.2 Common Command: *WAI (Wait to Continue)
  wait_to_continue:
    cmd: "*WAI"

  # IEEE 488.2 Common Command: *RQS (Request Control)
  request_control:
    query:
      cmd: "*RQS?"
      pattern: "(\\d+)"
    data_type: int

  # IEEE 488.2 Common Command: *TRG (Trigger)
  trigger:
    cmd: "*TRG"

  # IEEE 488.2 Common Command: *SRE (Status Byte Enable)
  status_byte_enable:
    cmd: "*SRE {}"
    query:
      cmd: "*SRE?"
      pattern: "(\\d+)"
    data_type: int

  # IEEE 488.2 Common Command: *ESE (Standard Event Status Enable)
  event_status_enable:
    cmd: "*ESE {}"
    query:
      cmd: "*ESE?"
      pattern: "(\\d+)"
    data_type: int
    timeout_s: 10

  # IEEE 488.2 Common Command: *LLO (Local Lockout)
  local_lockout:
    cmd: "*LLO"

  # IEEE 488.2 Common Command: *GTL (Go to Local)
  go_to_local:
    cmd: "*GTL"

  # IEEE 488.2 Common Command: *PSC (Power-On Status Clear)
  power_on_status_clear:
    cmd: "*PSC {}"
    query:
      cmd: "*PSC?"
      pattern: "(\\d+)"
    data_type: int

  # IEEE 488.2 Common Command: *PPC (Parallel Poll Configure)
  parallel_poll_configure:
    cmd: "*PPC {}"
    query:
      cmd: "*PPC?"
      pattern: "(\\d+)"
    data_type: int

  # IEEE 488.2 Common Command: *DCL (Device Clear)
  clear:
    cmd: "*DCL"

  # IEEE 488.2 Common Command: *SPD (Serial Poll Disable)
  serial_poll_disable:
    cmd: "*SPD"

  # IEEE 488.2 Common Command: *SPE (Serial Poll Enable)
  serial_poll_enable:
    cmd: "*SPE"

  # IEEE 488.2 Common Command: *ERR (Last Error)
  last_error:
    query:
      cmd: "*ERR?"
      pattern: "(.+)"
    data_type: string

messages:
  # IEEE 488.2 Common Command: *IDN (Identification)
  identification:
    query: "*IDN?"
    signals:
      manufacturer_name:
        pattern: "([^,]+),"
      model_number:
        pattern: "[^,]+,([^,]+),"
      serial_number:
        pattern: "[^,]+,[^,]+,([^,]+)"

API Reference

See zeloscloud.codecs.visa, zeloscloud.codecs.serial.messages, and zeloscloud.codecs.serial.signals in the API Reference.