usbtmc-lite 0.1.2

A minimal, readable USBTMC implementation for learning and simple use cases

usbtmc-lite

Minimal USBTMC (USB Test and Measurement Class) implementation for Python.

Communicate with USBTMC-compliant instruments via USB. Lightweight design with IEEE 488.2 block data transfer support.

Features

• Simple API for instrument communication (write/read/query)
• IEEE 488.2 block data transfer
• Status byte register access
• Keysight firmware mode unlock utility

Installation

pip install usbtmc-lite

Windows

Requires libusb-1.0.dll. Download from libusb releases.

Linux

sudo apt install libusb-1.0-0

You may need to configure udev rules:

# /etc/udev/rules.d/99-usbtmc.rules
SUBSYSTEM=="usb", ATTR{idVendor}=="0957", MODE="0666"

Quick Start

from usbtmc_lite import USBTMC
from usbtmc_lite.utils import find_usbtmc_devices, get_device, get_backend

backend = get_backend("./libusb-1.0.dll")  # Linux/macOS: get_backend()
devices = find_usbtmc_devices(backend=backend)
device = get_device(devices, vendor_id=0x0957, product_id=0x0618)

with USBTMC() as usbtmc:
    usbtmc.open(device)
    print(usbtmc.query("*IDN?"))

Examples

Basic Communication

from usbtmc_lite import USBTMC
from usbtmc_lite.utils import find_usbtmc_devices, get_device, get_backend

backend = get_backend("./libusb-1.0.dll")
devices = find_usbtmc_devices(backend=backend)
device = get_device(devices, vendor_id=0x0957, product_id=0x0618)

with USBTMC() as usbtmc:
    usbtmc.open(device)
    usbtmc.write("*RST")
    print(usbtmc.query("*IDN?"))

Multiple Identical Devices

from usbtmc_lite import USBTMC
from usbtmc_lite.utils import find_usbtmc_devices, get_device, get_backend

backend = get_backend()
devices = find_usbtmc_devices(backend=backend)

# Use serial number to distinguish
device = get_device(devices, 0x0957, 0x0618, serial_number="MY12345678")

with USBTMC() as usbtmc:
    usbtmc.open(device)
    print(usbtmc.query("*IDN?"))

Block Data Transfer

from usbtmc_lite import USBTMC
from usbtmc_lite.utils import find_usbtmc_devices, get_device, get_backend

backend = get_backend()
devices = find_usbtmc_devices(backend=backend)
device = get_device(devices, 0x0957, 0x0618)

with USBTMC() as usbtmc:
    usbtmc.open(device)
    
    # Upload waveform data
    usbtmc.write_block_data(":DATA:UPLOAD", waveform_bytes)
    
    # Download waveform data
    usbtmc.write(":DATA:DOWNLOAD?")
    data = usbtmc.read_block_data(timeout=10000)

Unlock Keysight Firmware Mode

Some Keysight USB modular instruments power on in firmware update mode:

from usbtmc_lite.utils import (
    get_backend,
    find_firmware_mode_devices,
    unlock_keysight_device,
    find_usbtmc_devices,
)
import time

backend = get_backend("./libusb-1.0.dll")

fw_devices = find_firmware_mode_devices(backend=backend)
if fw_devices:
    print(f"Found {len(fw_devices)} device(s) in firmware mode")
    unlock_keysight_device(fw_devices[0])
    time.sleep(3)  # Wait for USB re-enumeration

devices = find_usbtmc_devices(backend=backend)

API Reference

USBTMC

Method	Description
open(device)	Open connection to USB device
close()	Close connection
write(text)	Send text command
write_bytes(data)	Send raw bytes
read(length, timeout)	Read text response
read_bytes(length, timeout)	Read raw bytes
query(text, timeout)	Write and read
write_block_data(command, data)	Write IEEE 488.2 block data
read_block_data(timeout)	Read IEEE 488.2 block data
clear()	Clear device buffers
read_status_byte_register()	Read IEEE 488.2 status byte

Property	Description
opened	True if device is connected
device	Underlying PyUSB device object
terminator_write	Write terminator (default: \n)
terminator_read	Read terminator (default: \n)

Utilities

Function	Description
get_backend(dll_path=None)	Get libusb backend
find_usbtmc_devices(backend, vendor_id, product_id)	Find USBTMC devices
get_device(devices, vendor_id, product_id, serial_number)	Get specific device
find_firmware_mode_devices(backend, vendor_id)	Find devices in firmware update mode
unlock_keysight_device(device)	Switch Keysight device to USBTMC mode

License

Apache License 2.0