srsinst.dg645

Python instrument driver for the SRS DG645 Digital Delay Generator.

The DG645 is an 8-channel digital delay and pulse generator capable of generating precise time delays from 0 to 2000 seconds with 5 ps resolution. This driver provides a Pythonic interface to all remote-control commands over VXI-11, TCP/IP (raw socket), VISA, and RS-232 interfaces.

Installation

pip install srsinst.dg645

For development (editable install):

git clone https://github.com/thinkSRS/srsinst.dg645.git
cd srsinst.dg645
pip install -e .

Quick Start

from srsinst.dg645 import DG645, Keys

# Connect via VXI-11
dg = DG645('vxi11', '192.168.0.10')

# Connect via TCP/IP (raw socket, port 5025)
dg = DG645('tcpip', '192.168.0.10', 5025)

# Connect via RS-232
dg = DG645('serial', 'COM3', 9600)

# Connect via GPIB (requires pyvisa)
dg = DG645('visa', 'GPI0::15::INSTR')

# Set trigger source to internal at 1 kHz
dg.trigger.trigger_source = 'internal'
dg.trigger.trigger_rate = 1000.0

# Configure channel A: 100 ns after T0
dg.delays.delay['A']['T0'] = 100e-9

# Configure channel B: 500 ns after channel A
dg.delays.delay['B']['A'] = 500e-9

# Read back delay (returns reference channel index, delay time in seconds)
ref, t = dg.delays.delay['B']
print(f'Channel B: ref={ref}, delay={t*1e9:.1f} ns')

# Set output AB amplitude to 3.5 V, positive polarity
dg.outputs.amplitude['AB'] = 3.5
dg.outputs.polarity['AB'] = True

# Fire a single trigger
dg.trigger_now()

# Check instrument status
print(dg.get_status())

dg.disconnect()

Component Reference

Delay Channel Index Map

Delay channels can be addressed by name (string) or integer index:

# Equivalent ways to set channel A delay:
dg.delays.delay['A']['T0'] = 100e-9
dg.delays.delay[2][0] = 100e-9          # using integer indices

Output BNC Index Map

Output BNCs can be addressed by name (string) or integer index:

# Equivalent ways to set AB amplitude:
dg.outputs.amplitude['AB'] = 3.5
dg.outputs.amplitude[1] = 3.5           # using integer index

Available Interfaces

The RS-232 baud rate is set on the instrument front panel; the driver accepts any rate from [4800, 9600, 19200, 38400, 57600, 115200].

Integration Tests

The test suite requires a live DG645 connected to the PC.

Via VXI-11 or TCP/IP:

pytest -v -s tests/ --ip 192.168.0.10

Via RS-232:

pytest -v -s tests/ --port COM3

Via GPIB (or any VISA resource):

pytest -v -s tests/ --resource GPIB0::15::INSTR

Use -s to allow the connection-retry prompt when the initial connection fails.

License

MIT License — Copyright (c) 2026 Stanford Research Systems