So I just recently acquired an HHKB Pro 2. I make custom cables so obviously first thing I did was to make one for this bad boy. I had read that depending on the gauge of the wires HHKB’s can be tricky. My cables are made out of 28 gauge wires and the total length is around 8ft (total wire, more like a 3ft cable once coiled). Everything is then hooked to a USB hub that also has an extension going to the computer (this extension is heavy duty tho so it probably has 22 or 24 gauge wire. Every once in a while I get weird latency spikes with the board and it some time flat out “drive error” and disconnect on me. Is the cable to long? Or is the USB hub creating an issue?
Could be either really, there are a couple things:
- USB extenders are not good and not recommended in general. For USB-C you are actually not supposed to make them. If you could try a shorter one, or and active one, that might help. Anecdotally I’ve had a lot of issues with extenders over the years.
- The issue could also be with your custom cable, 8ft is long, but it’s not that long. Are your data lines done as a twisted pair and do you have proper shielding around it (connected to ground)?
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everything is shielded and grounded. The extension I did not make it’s just a generic amazon extension that goes between the hub under my desk to my PC
Is the hub USB 2 or USB 3?
You may try your cable without the hub just to check.
28AWG seems quite a small gage to me for a USB câble, maybe 26AWG would have been better, but I not an expert so take these words with a grain of salt.
Well on regular keyboard i’ve been using 28 gauge wire of over 10ft without any issue. The problem really seems to be in the power requirement of the HHKB (Topre boards in general I believe) The USB Hub is 3.0
On a side note, it’s important to say that the cable doesnt flat out not work. It works but every now and then (like 15-20min I get a quick disconnect and then it reconnects. The lenght of the cable might still be slightly too long for the gauge of wire used. I’ll try over a powered USB hub since that might help over come the extra wire from the USB hub itself.
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It might well be a power management issue.
Some basic USB hub ICs handle 200mA at most on the output ports if no external power is given.
So after testing with a powered USB hub I can confirm that my issue lies with the hub. If I plug it directly to the computer there is no wierd interaction, even with a longer custom cable.
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Problem solved then 
On my part I don’t usually plug my keyboard or mouse to a hub unless I want to test a keyboard PCB for the first time.
It happened to me to fry two USB ports on my previous computer by plugging a crappy board, now uses a hub for testing purposes and it acts like a fuse if something goes wrong 