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Instrument Server Hello World

Instrument Server Hello World is an Instrument Server microservice that implements one trivial command:

id_string?

This command returns the *IDN? response of a single, connected R&S Instrument.

Requirements

  • Python ~= 3.7
  • instrument-server ~= 1.3.7
  • An R&S Instrument

Install

Run scripts/install to install a known-good package and version set.

See the lock file for details:

requirements.txt.lock

Project Config File

Every instrument-server project is required to include a YAML config file. By convention, the config file must contain the following sections:

plugins: {...}
devices: {...}
# Translation Commands (Optional)
...

The config file for this project is hello_world.yaml. Each section of the file is explained below.

Plugins

This application does not include any plugins, and so the plugins value is an empty dictionary (no values).

plugins: {}

Devices

A single device named instrument is defined:

instrument:
  type:        socket
  address:     192.168.1.101
  port:        5025
  timeout:     5

Edit address to include the correct instrument IPV4 network IP address or hostname.

R&S instruments typically serve SCPI via a TCP socket on port 5025. This field is typically left unchanged.

Optionally, the timeout time (in seconds) can be adjusted. If omitted, the default value is 2 (seconds).

Optional: VISA

To instead communicate with instrument via VISA, replace the default instrument definition with:

instrument:
  type:         visa
  resource_str: "TCPIP::192.168.1.101::INSTR"
  open_timeout: 0
  timeout:      2000

Edit resource_str to include the correct instrument VISA Resource String.

Optionally, modify open_timeout and/or (read) timeout (in milliseconds).

Commands

An instrument-server project file may include Translation command definition(s). hello_world.yaml defines one Translation command:

id_string?:
  - instrument: "*IDN?"

The key 'id_string?' defines the command syntax. The trailing ? indicates that this is a query. This convention should be familiar to SCPI users.

Translation query commands return the result of the last SCPI query.

In the example above, there is only one SCPI command sent to instrument: *IDN?. The result of this query is returned by id_string?.

Start

Run scripts/start to serve hello_world.yaml on all network interfaces on port 9000.

scripts/start calls the instrument-server Command Line Interface (CLI), which provides additional settings.

From instrument-server --help:

usage: instrument-server [-h] [--address ADDRESS] [--port PORT]
                         [--termination TERMINATION] [--debug-mode]
                         config_filename

Command Line Interface for starting Instrument Server microservices

positional arguments:
  config_filename

optional arguments:
  -h, --help            show this help message and exit
  --address ADDRESS, -a ADDRESS
                        Set listening address. Default: 0.0.0.0
  --port PORT, -p PORT  Set listening port. Default: random
  --termination TERMINATION, -t TERMINATION
                        Set the termination character. Default: "\n"
  --debug-mode, -d      print debug info to stdout

Client Script

The client.py script is provided for testing. It connects to the Instrument Server Hello World microservice, queries id_string?, then prints the result.

client.py can be run from the command line as follows:

scripts/start-in-background
# => Running on 0.0.0.0:9000...

# run client
python client.py
# => id_string?
# => Rohde-Schwarz,ZNBT40-8Port,1332900244900059,3.15

Next Steps: Input Arguments

Translation commands may include position-based input arguments. These inputs are available to the associated SCPI commands via f-string syntax.

Here is a hypothetical example of a Translation command that configures the power level of the generator and analyzer.

set_power power_dBm:
  - generator: "SOUR:POW:POW     {power_dBm}"
  - analyzer:  "DISP:TRAC:Y:RLEV {power_dBm}"

References