Skip to content

Experiment: AFG to DSOX Loopback Validation (Plug-and-Play)

This document summarizes the end-to-end validation of the integrated signal chain between the Tektronix AFG3022C (Signal Source) and the Keysight DSOX2002A (Capture). This specific experiment focused on Zero-Config Discovery (AUTO Mode).

Hardware Setup

  • Source: Tektronix AFG3022C connected via LAN.
  • Capture: Keysight DSOX2002A connected via USB.
  • Interconnect: BNC Output 1 (AFG) → BNC Input 1 (DSOX).

Essential Device Configuration

For the automated discovery to succeed on macOS, the following physical settings were required:

Keysight DSOX2002A (USB Discovery)

[!IMPORTANT] Enable Compatibility Mode: By default, the DSOX may not appear as a standard USB-TMC device. 1. Press the [Utility] key on the front panel. 2. Select I/O → USB. 3. Ensure the mode is set to USB-TMC (or "Compatibility Mode" depending on firmware version). 4. Once enabled, the device will appear as USB0::0x0957::0x179B::...::INSTR.

Tektronix AFG3022C (LAN Discovery)

  • Static IP: Assigned 169.254.105.101 for direct peer-to-peer connection.
  • VXI-11: Ensure the VXI-11 server is enabled in the network settings.

The "AUTO" Discovery Process

We validated the HAL's ability to find these instruments without any hardcoded addresses.

How it works (Step-by-Step):

  1. USB Scan: The HAL calls pyvisa.ResourceManager().list_resources() to find the DSOX on the USB bus.
  2. Smart LAN Probe: If an instrument (like the AFG) isn't on USB, the HAL performs a Smart ARP Scan of the local subnet (169.254.x.x).
  3. Identity Verification: The HAL connects to every found address and queries *IDN?.
  4. Type-Aware Routing: Even if the scan finds multiple Keysight or Tektronix devices, it only returns a match that fits the requested category (e.g., ignoring a Scope when a Signal Generator is requested).

Validation Script

The final validation used zero hardcoded addresses:

from instrumation.factory import get_instrument

# 1. The HAL 'hunts' for the Signal Generator and Scope
afg = get_instrument("AUTO", "SG") 
dso = get_instrument("AUTO", "SCOPE")

print(f"AFG Found at: {afg.resource}")
print(f"DSO Found at: {dso.resource}")

# 2. Standard Loopback Procedure
afg.preset()
afg.set_waveform("SQU")
afg.set_frequency(100e3)
afg.set_voltage(1.5)
afg.set_output(True)

dso.auto_scale()
trace = dso.get_waveform(1)

# 4. Data Analysis & Visualization
import numpy as np
import matplotlib.pyplot as plt

y_data = np.array(trace.value)
x_data = np.linspace(0, 1, len(y_data)) 

plt.figure(figsize=(12, 6))
plt.plot(x_data, y_data, color='#007AFF', label='CH1 (AFG Output)')
plt.title("AFG to DSOX Loopback Validation")
plt.xlabel("Normalized Time")
plt.ylabel("Amplitude (Volts)")
plt.grid(True, linestyle='--', alpha=0.7)
plt.savefig("../assets/afg_dso_loopback.png")
plt.show()

# 5. Cleanup
afg.set_output(False)

Results

The experiment successfully verified that AUTO mode is robust for both high-speed USB-TMC and network-based VXI-11 protocols.

Visual Validation

AFG to DSOX Loopback

Conclusion

The instrumation HAL now supports true plug-and-play operation for the entire RF test bench. By combining ARP probing with USB scanning, the system eliminates the need for manual IP configuration in test scripts.