SCPI Virtual Instrument Server

This project simulates network-connected scientific instruments supporting the SCPI standard. It runs a webserver with a port open per instrument. Every connected user (distinguished by IP) gets their own copy of the instrument and can interact with it independently of the others.

Usage

from server import Server, Experiment
from instrument import VirtualInstrument, CommandTree, get_float_value, get_bool_value, hookable

class Voltmeter(VirtualInstrument):
    commands = CommandTree(VirtualInstrument.commands)
    
    @commands.add(':VOLTAGE?')
    def get_voltage(self):
        return '{:.2f}'.format(self.voltage)
    
    def __init__(self):
        super().__init__("Voltmeter")
        
    def reset(self):
        self.voltage = 0
        super().reset()

class CurrentSource(VirtualInstrument):

    commands = CommandTree(VirtualInstrument.commands)
    
    @commands.add(':current?')
    def get_current(self):
        return '{:.2f}'.format(self.current)
    
    @commands.add(':current')
    @hookable('current')
    def set_current(self, parsed_value):
        self.current = get_float_value(parsed_value, default=0, min_max=(-10, 10), units='A')

    def __init__(self):
        super().__init__("Current source")

    def reset(self):
        self.current = 0

class OhmExperiment(Experiment):
    ports = (PORT_V := 9001,
             PORT_I := 9002)

    def __init__(self, client_ip, resistance):
        super().__init__(client_ip)
        self.resistance = resistance
        self.instruments = {
            self.PORT_V: Voltmeter(),
            self.PORT_I: CurrentSource()
            }
        self.instruments[self.PORT_I].add_hook(self.sync)
                
    def sync(self, *args):
        self.instruments[self.PORT_V].voltage = \
            self.instruments[self.PORT_I].current * self.resistance

if __name__ == "__main__":

    server = Server(OhmExperiment, local=True, resistance=1e3)
    try:
        server.run()
    except Exception:
        server.shutdown_event.set()
        raise

We can now connect to the server and run code like

import pyvisa
rm = pyvisa.ResourceManager()
voltmeter = rm.open_resource('TCPIP::127.0.0.1::9001::SOCKET', read_termination='\n')
current_source = rm.open_resource('TCPIP::127.0.0.1::9002::SOCKET', read_termination='\n')
current_source.write(":CURR 3")
resistance = voltmeter.query(":VOLT?")/3