How I gave my old test box a second life with a browser GUI

I did something similar last year with mine, except I stopped at a Python script instead of a full web page. My goal was just using it as a cheap signal source for testing an amplifier I was repairing, so I never needed the scope side at all. The driver thing matches what I saw on Linux too. I had to add a udev rule before anything except the vendor software could open the device, and it took me an embarrassing evening of reading forum threads to figure that out.

Your suggestion about starting with one channel and building out is exactly how it went for me, just by accident. I got the waveform generator working first because that was all I needed, and when I later wanted to add a simple voltmeter readout it was easy because the structure was already there.

The one thing I'd add is that I keep the vendor software on a seprate old laptop that never touches the hardware. I use it for the calibration routines and firmware updates, then do everything else with my own setup. Some of the calibration data lives in the device and I did not want to risk writing garbage into it, so I let the official tool handle anything that writes to persistent storage.

Ran into a fun quirk when I tried the browser route on my own bench gear last winter. The bulk transfers would stall out after a few seconds untill I dropped the packet size way down. Turns out asking for more than 16 KB per transfer was tripping somethig in the USB stack, and once I capped it everything ran clean for hours. No idea if that hits every chipset but it's the first thing I'd check if the stream stutters. Also worth keeping a serial console open on the side while you debug, watching the raw bytes scroll by caught a framing bug for me that the web page was happily hiding.

I keep every synthesized bitstream in a dated folder next to the exact source that produced it, wich came out of losing a known good build to a careless edit early on. Rolling back to the old file and diffing the two versions of the source found the culprit in a couple of minutes, which beat re-reading everything line by line. Curious whether you keep your constraint file under version control as well, because mine had drifted from the actual board wiring and I chased a phantom connection bug for a whole afternoon before I thought to check it.