Python IVI Readme

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

• DC Power Supplies (dcpwr)
  • Tektronix PS2520G/PS2521G
• Function Generators (fgen)
  • Tektronix AWG2000 series
• RF Signal Generators (rfsiggen)
  • Agilent 8642 A/B
• Oscilloscopes (scope)
  • Agilent InfiniiVision 7000A series

Python IVI can use linux-gpib and Python VXI11 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 VXI11. If it starts with GPIB, it will attempt to use linux-gpib's python interface. Integration with PyVISA is planned, but not currently supported.

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.

This sample Python code will use Python IVI connect to an Agilent MSO7104A over LXI (VXI11), 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")
# 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()

This sample Python code will use Python IVI to connect to a Tektronix AWG2021 through a GPIB to VXI11 bridge or serial (pySerial), 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 E2050A GPIB to VXI11 bridge
awg = ivi.tektronix.tektronixAWG2021("TCPIP0::192.168.1.104::gpib,10::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.gain = 0.0
# sample rate 128 MHz
arb.arbitrary.sample_rate = 128e6
# enable ouput
awg.outputs[0].enabled = True