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For more information and updates: http://alexforencich.com/wiki/en/python-ivi/start
GitHub repository: https://github.com/python-ivi/python-ivi
Google group: https://groups.google.com/d/forum/python-ivi
Python IVI is a Python-based interpretation of the Interchangeable Virtual Instrument standard from the IVI foundation.
Python IVI can use Python VXI-11, Python USBTMC, PyVISA, pySerial and linux-gpib to connect to instruments. The implementation of the initialize method takes a VISA resource string and attempts to connect to an instrument. If the resource string starts with TCPIP, then Python IVI will attempt to use Python VXI-11. If it starts with USB, it attempts to use Python USBTMC. If it starts with GPIB, it will attempt to use linux-gpib's python interface. If it starts with ASRL, it attemps to use pySerial. Python IVI will fall back on PyVISA if it is detected. It is also possible to configure IVI to prefer PyVISA over the other supported interfaces.
As the IVI standard only specifies the API for C, COM, and .NET, a Python implementation is inherently not compliant and hence this is not an implementation of the standard, but an interpretation that tries to remain as faithful as possibe while presenting a uniform, easy-to-use, sensible, python-style interface.
The Python IVI library is a Pythonized version of the .NET and COM IVI API specifications, with the CamelCase for everything but the class names replaced with lowercase_with_underscores. The library most closely follows the .NET standard, with the calls that would require the .NET helper classes follwing the corresponding COM specifications. There are some major deviations from the specification in order to be consistent with the spirit of the other IVI specifications. The fgen class is the most obvious example of this, using properties instead of the getters and setters as required by the IVI specification.
Extract and run
# python setup.py install
Python IVI does not contain any IO drivers itself. In order to communicate with an instrument, you must install one or more of the following drivers:
Python VXI11 provides a pure python TCP/IP driver for LAN based instruments that support the VXI11 protocol. This includes most LXI instruments and also devices like the Agilent E2050 GPIB to LAN converter.
Home page: http://www.alexforencich.com/wiki/en/python-vxi11/start
GitHub repository: https://github.com/python-ivi/python-vxi11
Python USBTMC provides a pure python USBTMC driver for instruments that support the USB Test and Measurement Class. Python USBTMC uses PyUSB to connect to the instrument in a platform-independent manner.
Home page: http://alexforencich.com/wiki/en/python-usbtmc/start
GitHub repository: https://github.com/python-ivi/python-usbtmc
A Python package for support of the Virtual Instrument Software Architecture (VISA), in order to control measurement devices and test equipment via GPIB, RS232, or USB.
Home page: http://pyvisa.readthedocs.org/
Python IVI will use PyVISA as a fallback for all connections, if it is detected. If a connection with PyVISA is preferred, then there are two ways of changing this. First, the prefer_pyvisa option can be set when initalizing an instrument:
mso = ivi.agilent.agilentMSO7104A("TCPIP0::192.168.1.104::INSTR", prefer_pyvisa = True)
or equivalently:
mso = ivi.agilent.agilentMSO7104A()
mso.initialize("TCPIP0::192.168.1.104::INSTR", prefer_pyvisa = True)
Second, the prefer_pyvisa option can be set globally:
ivi.set_prefer_pyvisa(True)
mso = ivi.agilent.agilentMSO7104A("TCPIP0::192.168.1.104::INSTR")
Python IVI provides an interface wrapper for the Linux GPIB driver. If the Linux GPIB driver and its included Python interface available, Python IVI can use it to communicate with instruments via any GPIB interface supported by Linux GPIB.
Home page: http://linux-gpib.sourceforge.net/
Python IVI provides an interface wrapper for the pySerial library. If pySerial is installed, Python IVI can use it to communicate with instruments via the serial port.
Home page: http://pyserial.sourceforge.net/
Python IVI has a built-in help feature. This can be used in three ways:
Call the help method with no parameters:
import ivi instr = ivi.Driver() instr.help()
This will print a list of all of the available methods and properties, like this:
close initialized initialize identity.get_supported_instrument_models identity.get_group_capabilities identity.specification_major_version ...
The higher level groups can also be passed to the help method:
import ivi instr = ivi.Driver() instr.help(instr.identity)
This will output everything inside of the sub group:
get_supported_instrument_models get_group_capabilities specification_major_version ...
Finally, individual methods and properties can be passed as strings:
import ivi
instr = ivi.Driver()
instr.help("identity.supported_instrument_models")
This will result in the complete documentation:
Returns a comma-separated list of names of instrument models with which the IVI specific driver is compatible. The string has no white space ...
This sample Python code will use Python IVI to connect to an oscilloscope (either an Agilent MSO7104A or a Tektronix MDO4104) over LXI (VXI-11) or USBTMC, configure the timebase, trigger, and channel 1, capture a waveform, and read it out of the instrument.
# import Python IVI
import ivi
# connect to scope
scope = ivi.agilent.agilentMSO7104A("TCPIP0::192.168.1.104::INSTR")
#scope = ivi.tektronix.tektronixMDO4104("TCPIP0::192.168.1.108::INSTR")
#scope = ivi.agilent.agilentMSO7104A("USB0::2391::5973::MY********::INSTR")
#scope = ivi.tektronix.tektronixMDO4104("USB0::1689::1036::C******::INSTR")
# configure timebase
scope.acquisition.time_per_record = 1e-3
# configure triggering
scope.trigger.type = 'edge'
scope.trigger.source = scope.channels[0]
scope.trigger.coupling = 'dc'
scope.trigger.edge.slope = 'positive'
scope.trigger.level = 0
# configure channels
for ch in scope.channels[0:1]:
ch.enabled = True
ch.offset = 0
ch.range = 4
ch.coupling = 'dc'
# initiate measurement
scope.measurement.initiate()
# read out channel 1 waveform data
waveform = scope.channels[0].measurement.fetch_waveform()
# measure peak-to-peak voltage
vpp = scope.channels[0].measurement.fetch_waveform_measurement("voltage_peak_to_peak")
# measure phase
phase = scope.channels[0].measurement.fetch_waveform_measurement("phase", scope.channels[1])
# save screenshot to file
png = scope.display.fetch_screenshot()
with open('screenshot.png', 'wb') as f:
f.write(png)
# save setup to file
setup = scope.system.fetch_setup()
with open('setup.dat', 'wb') as f:
f.write(setup)
# restore setup from file
with open('setup.dat', 'rb') as f:
setup = f.read()
scope.system.load_setup(setup)
This sample Python code will use Python IVI to connect to a Tektronix AWG2021, generate a sinewave with numpy, and transfer it to channel 1.
# import Python IVI
import ivi
# import numpy
from numpy import *
# connect to AWG2021 via GPIB
#awg = ivi.tektronix.tektronixAWG2021("GPIB0::25::INSTR")
# connect to AWG2021 via E2050A GPIB to VXI11 bridge
awg = ivi.tektronix.tektronixAWG2021("TCPIP0::192.168.1.105::gpib,25::INSTR")
# connect to AWG2021 via serial
#awg = ivi.tektronix.tektronixAWG2021("ASRL::/dev/ttyUSB0,9600::INSTR")
# create a waveform
n = 128
f = 1
a = 1
wfm = a*sin(2*pi/n*f*arange(0,n))
# transfer to AWG2021
awg.outputs[0].arbitrary.create_waveform(wfm)
# 2 volts peak to peak
awg.outputs[0].arbitrary.gain = 2.0
# zero offset
awg.outputs[0].arbitrary.offset = 0.0
# sample rate 128 MHz
arb.arbitrary.sample_rate = 128e6
# enable ouput
awg.outputs[0].enabled = True
This sample Python code will use Python IVI to connect to an Agilent E3649A and configure an output.
# import Python IVI
import ivi
# connect to E3649A via GPIB
#psu = ivi.agilent.agilentE3649A("GPIB0::5::INSTR")
# connect to E3649A via E2050A GPIB to VXI11 bridge
psu = ivi.agilent.agilentE3649A("TCPIP0::192.168.1.105::gpib,5::INSTR")
# connect to E3649A via serial
#psu = ivi.agilent.agilentE3649A("ASRL::/dev/ttyUSB0,9600::INSTR")
# configure output
psu.outputs[0].configure_range('voltage', 12)
psu.outputs[0].voltage_level = 12.0
psu.outputs[0].current_limit = 1.0
psu.outputs[0].ovp_limit = 14.0
psu.outputs[0].ovp_enabled = True
psu.outputs[0].enabled = True
It is also possible to control multiple instruments. This example configures an Agilent ESG E4433B vector signal generator to output an IQ modulated multitone waveform which is then received on an Agilent 8593E spectrum analyzer.
# import Python IVI
import ivi
# import numpy
import numpy as np
# connect to E4433B via E2050A
esg = ivi.agilent.agilentE4433B("TCPIP::192.168.1.110::gpib,19::INSTR")
# connect to 8593E via E2050A
sa = ivi.agilent.agilent8593E("TCPIP::192.168.1.110::gpib,18::INSTR")
# create multitone IQ waveform
n = 2000
f1 = 1
a1 = 0.5
f2 = 3
a2 = 0.5
t = np.arange(0,n)
yi = a1*np.sin(2*np.pi/n*f1*t)+a2*np.sin(2*np.pi/n*f2*t)
yq = np.zeros(n)
# configure ESG
esg.rf.frequency = 4e9
esg.rf.level = -10
esg.digital_modulation.arb.write_waveform('wfm', yi, yq)
esg.digital_modulation.arb.selected_waveform = 'wfm'
esg.digital_modulation.arb.clock_frequency = 10e6
esg.iq.source = 'arb_generator'
esg.iq.enabled = True
esg.rf.output_enabled = True
# configure SA
sa.frequency.configure_center_span(4e9, 100e3)
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