Python IVI Readme

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

Introduction

Python IVI is a Python-based interpretation of the Interchangeable Virtual Instrument standard from the IVI foundation.

Included drivers

• Oscilloscopes (scope):
  • Agilent InfiniiVision 2000A X-series
  • Agilent InfiniiVision 3000A X-series
  • Agilent InfiniiVision 4000A X-series
  • Agilent InfiniiVision 6000A series
  • Agilent InfiniiVision 7000A/B series
  • Agilent Infiniium 90000A/90000X series
  • LeCroy WaveRunner Xi-A series
• Digital Multimeters (dmm):
  • Agilent 34401A
  • Agilent 34410A
• Function Generators (fgen):
  • Agilent InfiniiVision 2000A X-series (Wavegen option)
  • Agilent InfiniiVision 3000A X-series (Wavegen option)
  • Agilent InfiniiVision 4000A X-series (Wavegen option)
  • Tektronix AWG2000 series
• DC Power Supplies (dcpwr):
  • Agilent E3600A series
  • Agilent 603xA series
  • Chroma 62000P series
  • Rigol DP800 series
  • Rigol DP1000 series
  • Tektronix PS2520G/PS2521G
• RF Power Meters (pwrmeter):
  • Agilent 436A
  • Agilent 437B
• Spectrum Analyzers (specan):
  • Agilent 859xA/B series
  • Agilent 859xE/EM/C/L series
• RF Signal Generators (rfsiggen):
  • Agilent 8340/1 A/B
  • Agilent 8642 A/B
  • Agilent ESG E4400B series
• Other
  • Agilent 8156A optical attenuator
  • Agilent 86140B series optical spectrum analyzer
  • Agilent 85644/5A tracking source
  • Colby Instruments PDL10A Programmable Delay Line
  • DiCon Fiberoptics GP700 Programmable Fiberoptic Instrument
  • JDS Uniphase TB9 Series Optical Grating Filter
  • Tektronix AM5030 programmable current probe amplifier
  • Tektronix OA5000 series optical attenuator

Instrument communication

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.

A note on standards compliance

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.

Requirements

• Python 2 or Python 3
• NumPy
• One or more communication extensions

Installation

Extract and run

# python setup.py install

Instrument Communication Extensions

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

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

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

PyVISA

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")

Linux GPIB

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/

pySerial

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/

Built-in Help

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
...

Usage examples

This sample Python code will use Python IVI to connect to an Agilent MSO7104A over LXI (VXI-11), configure the timebase, trigger, and channel 1, capture a waveform, and read it out of the instrument.

# import Python IVI
import ivi
# connect to MSO7104A via LXI
mso = ivi.agilent.agilentMSO7104A("TCPIP0::192.168.1.104::INSTR")
# connect to MSO7104A via USBTMC
#mso = ivi.agilent.agilentMSO7104A("USB0::2391::5973::MY********::INSTR")
# configure timebase
mso.acquisition.time_per_record = 1e-3
# configure triggering
mso.trigger.type = 'edge'
mso.trigger.source = 'channel1'
mso.trigger.coupling = 'dc'
mso.trigger.edge.slope = 'positive'
mso.trigger.level = 0
# configure channel
mso.channels['channel1'].enabled = True
mso.channels['channel1'].offset = 0
mso.channels['channel1'].range = 4
mso.channels['channel1'].coupling = 'dc'
# initiate measurement
mso.measurement.initiate()
# read out channel 1 waveform data
waveform = mso.channels[0].measurement.fetch_waveform()
# measure peak-to-peak voltage
vpp = mso.channels[0].measurement.fetch_waveform_measurement("voltage_peak_to_peak")
# measure phase
phase = mso.channels['channel1'].measurement.fetch_waveform_measurement("phase", "channel2")
# save screenshot to file
png = mso.display.fetch_screenshot()
with open('screenshot.png', 'wb') as f:
    f.write(png)
# save setup to file
setup = mso.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()
mso.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)