Python Laboratory Hardware Abstraction Layer, Py-Lab-HAL

Py-Lab-HAL is a multi-platform Python library for Lab Test Equipment Control and Automation. It has been run and tested under Windows, Linux, and Mac.

We support some common and uncommon lab test equipment:

• DC Power Supply
• Battery Emulator
• DMM
• Electronic Load
• Function Generator
• Light Panel
• Power Meter
• Generic USB Relay
• Remote Power Switch
• Oscilloscope
• SMU
• Spectroradiometer
• Stepper Motor
• Temperature Chamber
• Robot Arm

Py-Lab-HAL also supports multiple equipment interfaces:

• Serial
• VXI-11
• USB
• Socket
• HiSLIP (Coming Soon...)

Requirements

1. OS: Windows, Mac, or Linux
2. Python 3.9+
3. NI-VISA if running on Windows
   1. Download Here

Installation

We currently only offer installing from GitHub. PyPi install coming soon!

git clone https://github.com/google/py-lab-hal.git
cd py-lab-hal
pip install .

For linux users, you will have to run an extra step:

echo "SUBSYSTEM==\"usb\", MODE=\"0666\", GROUP=\"usbusers\"" | sudo tee -a /etc/udev/rules.d/99-usbusers.rules

to configure your USB device access or you won't be able to see instruments over an USB connection. You might have to restart the computer after entering the command.

Getting Started

Let's get our basic imports out of the way:

from py_lab_hal import builder
from py_lab_hal.cominterface import cominterface

The builder helps us build the instrument while cominterface defines the communication interface in which the host/test computer will use to talk to the test equipment.

Creating the Builder

Creating the builder is a simple one-liner:

build = builder.PyLabHALBuilder()

Configuring the cominterface

Since Py-Lab-HAL is supporting various interfaces, there are quite a lot of parameters to set up across each interface. For details, check out the source.

To see what is connected to your system and their resource data, you can use our built-in utility in a terminal:

python3 -m py_lab_hal.scan

This will scan and list out all the visa_resources available to your system.

Configuring USB and VXI-11

An USB or VXI-11 connection is straight-forward, just fill in the visa_resource you need :

build.connection_config = cominterface.ConnectConfig(
    visa_resource='USB0::10893::769::MY59006118::0::INSTR',
)

Configuring Socket

For Socket connections, you will need to know the socket_host and socket_port of your instrument. This will be filled into an addition config, NetworkConfig, which you can define separately, or in-line as we have done here:

build.connection_config = cominterface.ConnectConfig(
    network=cominterface.NetworkConfig(
        host='192.168.11.11',
        port=5025,
    ),
)

Configuring Serial

Setting up serial connection is the most involved as it contains the most parameters. As in socket, you will need to fill out an addition config, SerialConfig. If you are using all default values, then you can just pass in SerialConfig as is, if not, you will need to set it up. The parameters and their defaults are as follows:

• Baud Rate
  • Default = 9600

cominterface.SerialConfig(baud_rate = 9600)

• Data Bits
  • Default = 8

cominterface.SerialConfig(data_bits = 8)

• Stop Bits
  • Default = 1 or cominterface.StopBits.ONE
  • Select from:

cominterface.StopBits.ONE
cominterface.StopBits.ONE_POINT_FIVE
cominterface.StopBits.TWO

#Usage
cominterface.SerialConfig(stop_bits = cominterface.StopBits.ONE)

• Parity
  • Default = 'N' or cominterface.Parity.NONE
  • Select from:

cominterface.Parity.EVEN
cominterface.Parity.NONE
cominterface.Parity.SPACE
cominterface.Parity.MARK
cominterface.Parity.ODD

#Usage
cominterface.SerialConfig(parity = cominterface.Parity.NONE)

• Flow Control
  • Default = 0 or 'cominterface.ControlFlow.NONE'
  • Select from:

cominterface.ControlFlow.DTR_DSR
cominterface.ControlFlow.RST_CTS
cominterface.ControlFlow.NONE
cominterface.ControlFlow.XON_XOFF

#Usage
cominterface.SerialConfig(flow_control = cominterface.ControlFlow.RST_CTS)

A small example of overriding some of the default values when setting up SerialConfig:

build.connection_config = cominterface.ConnectConfig(
    visa_resource='ASRL/dev/ttyUSB0::INSTR',
    serial_config=cominterface.SerialConfig(
        baud_rate=115200,
        flow_control=cominterface.ControlFlow.RST_CTS,
    ),
)

Build the Instrument Object

Now that the builder has been instantiated and cominterface setup, it is time to build and instantiate the actual instrument!

But first we need to make sure our initalization call to the instrument is set up correctly:

Instrument Config

The instrument configuration and their defaults are listed below:

build.instrument_config.reset = True
build.instrument_config.clear = True
build.instrument_config.idn = True
build.instrument_config.auto_init = True

reset, clear, and idn are standard VISA SCPI commands, while auto_init is a Py-Lab-HAL command. The first 3 commands and their SCPI equivalents are as follows:

• reset = *RST
• clear = *CLR
• idn = *IDN?

auto_init determines whether to open a connection to the instrument after builder instantiates the object. If you select false, you will have to issue a separate call to open a connection to the instrument.

Note: reset, clear, and idn only applies to VISA SCPI instruments. For non-VISA instruments, all 3 of these flags must be set to False or you will get an error with the instrument. A few examples of a non-VISA instrument would be: robot arm, panel light, temp chamber, and generic USB relay.

Build Instrument

To finish building the instrument, we will invoke the build_instrument function:

build.build_instrument(builder.FOLDER_NAME.MODULE_NAME)

Where:

• FOLDER_NAME = The type of equipment, e.g., DMM, DC Power Supply, etc.
• MODULE_NAME = The module or model name of the instrument, e.g., Keysight, Tektronix, Lecroy, etc. The MODULE_NAME follows the convention of
• MAKER_MODEL, for example: KEYSIGHT_N6705C in all caps.

Usage:

dcpsu = build.build_instrument(builder.DCPowerSupply.KEYSIGHT_N6705C)
dmm = build.build_instrument(builder.DMM.AGILENT_34465A)

For details on putting it all together, see the example below and our demo folder for more examples.

Example

import time
from py_lab_hal import builder
from py_lab_hal.cominterface import cominterface

build = builder.PyLabHALBuilder()

build.connection_config = cominterface.ConnectConfig(
  visa_resource='USB0::10893::769::MY59006118::0::INSTR',
)
dmm = build.build_instrument(builder.DMM.AGILENT_34465A)

build.connection_config = cominterface.ConnectConfig(
  visa_resource='ASRL/dev/ttyUSB0::INSTR',
  serial_config=cominterface.SerialConfig()
)
dcpsu = build.build_instrument(builder.DCPowerSupply.GWIN_PST3202)

try:
  dcpsu.set_output(1, 5, 1)
  dcpsu.enable_output(1, True)
  print('output 5 V')
  time.sleep(1)
  for i in range(5):
    print(dmm.read())

  dcpsu.set_output(1, 6, 1)
  dcpsu.enable_output(1, True)
  print('output 6 V')
  time.sleep(1)
  for i in range(5):
    print(dmm.read())

finally:
  dmm.close()
  dcpsu.close()

Disclaimer

This is not an official Google product.