ARCnet RS485-to-USB converter?

I'm trying to figure out a way to observer/sniff/analyze ARCnet communications.
Specifically, ARCnet at 156k baud, via RS-485.

I understand that the ARCnet co-processor chip is tasked with many of the layer 2-4 levels of communications, what I don't understand is:

  • Why can you not use a generic RS485-to-USB converter and use software (a driver, perhaps?) to mimic the layer 2-4 aspects
    • Pretending to be an imposter ARCnet-compliant device, mostly for the purposes a comms scanner, similar to Modbus or BACnet (YABE) explorer tools
    • Make a proper RS485-to-USB converter with an ARCnet co-processor on it.

Whenever I search for such things along the lines of ARCnet to USB converter, I get a bunch of rubbish. It's a bit odd. The closest thing I can find is a Contemporary Controls interface ($400) or decades old conversations about ARCnet to ethernet, primarily coax networks for old computer systems.

I assume if you put oscilloscope probes on an ARC156k network, it would have transmitted bits, just like any other protocol. Would it be possible (not necessarily easy!) to read those bits via RS485/USB dongle and 'sniff' an ARCnet BACnet network?

I guess I'm trying to figure out if the lack of what I'm looking for is a due to technical difficulties or simply lack of demand for a niche product.
 
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