3 ms·

The Thunderscope story had a comment about USB3 sampling as well. Here, you cite "check signal integrity," as a reason. I'm curious. Is USB3 signal integrity

The Thunderscope story had a comment about USB3 sampling as well. Here, you cite "check signal integrity," as a reason. I'm curious. Is USB3 signal integrity really an active area of research or troubleshooting? I would have figured this has all been well characterized and mostly solved by device manufacturers selling working USB3 components by the boat load for years now.

tverbeure 1y ago
The ICs are a solved problem, but hobbyists like me designing their own USB3 capable PCB is a different story. Whether or not having a high BW scope would be helpful to detect signal integrity issue is not clear to me: measuring these kind of signal is an art in itself.
- topspin 1y ago
  "Whether or not having a high BW scope would be helpful to detect signal integrity issue is not clear to me" Indeed. Even if you have an instrument, and the skill to operate it and produced a meaningful result that reveals some problem, that doesn't spell out a solution. It may help, but high frequency is subtle.
crote 1y ago
High-speed signals are incredibly fragile. The chips themselves are a solved problem, but you still need quite a bit of skill and experience to design a PCB for them. It's quite easy to mess up in subtle ways which look like they should work, but actually ruin your signal to the point of being completely unusable. If you're designing a board, not being able to look at its signals is a major limitation. Is something wrong with the transmitter, receiver, cable, connector, pcb, firmware, driver? Who knows! It doesn't work, and that's all you're going to get. Have fun randomly tweaking stuff in the hope that it is magically going to work.
amelius 1y ago
Yes, I experienced a lot of trouble with USB3 cables, cameras, and storage devices in scientific/industrial environments where lots of data is transferred. There seems to be no way to debug this stuff unless you are a big company that can pay large sums of money.
photon_rancher 1y ago
The PCB is easy to screw up, so are the cables. And scopes that go that high are expensive but customers expect USB3 even on low volume low cost products so there’s definitely advantages. There can even just be manufacturing defects the FR4 weave that mess up SI that you might want to check for as a QA step on the assembly line. For hi volume that gets slow or expensive
labcomputer 1y ago
> I'm curious. Is USB3 signal integrity really an active area of research or troubleshooting? Yes, but: You don’t need a general purpose realtime high bandwidth scope for verifying signal integrity. You can use an equivalent time sampling scope (~10ksps to 100ksps) to measure the eye diagram and ensure that the received eye matches the mask specified by the spec.

tverbeure 1y ago

The ICs are a solved problem, but hobbyists like me designing their own USB3 capable PCB is a different story. Whether or not having a high BW scope would be helpful to detect signal integrity issue is not clear to me: measuring these kind of signal is an art in itself.

topspin 1y ago
"Whether or not having a high BW scope would be helpful to detect signal integrity issue is not clear to me" Indeed. Even if you have an instrument, and the skill to operate it and produced a meaningful result that reveals some problem, that doesn't spell out a solution. It may help, but high frequency is subtle.

crote 1y ago

High-speed signals are incredibly fragile. The chips themselves are a solved problem, but you still need quite a bit of skill and experience to design a PCB for them. It's quite easy to mess up in subtle ways which look like they should work, but actually ruin your signal to the point of being completely unusable. If you're designing a board, not being able to look at its signals is a major limitation. Is something wrong with the transmitter, receiver, cable, connector, pcb, firmware, driver? Who knows! It doesn't work, and that's all you're going to get. Have fun randomly tweaking stuff in the hope that it is magically going to work.

amelius 1y ago

Yes, I experienced a lot of trouble with USB3 cables, cameras, and storage devices in scientific/industrial environments where lots of data is transferred. There seems to be no way to debug this stuff unless you are a big company that can pay large sums of money.

photon_rancher 1y ago

The PCB is easy to screw up, so are the cables. And scopes that go that high are expensive but customers expect USB3 even on low volume low cost products so there’s definitely advantages. There can even just be manufacturing defects the FR4 weave that mess up SI that you might want to check for as a QA step on the assembly line. For hi volume that gets slow or expensive

labcomputer 1y ago

> I'm curious. Is USB3 signal integrity really an active area of research or troubleshooting? Yes, but: You don’t need a general purpose realtime high bandwidth scope for verifying signal integrity. You can use an equivalent time sampling scope (~10ksps to 100ksps) to measure the eye diagram and ensure that the received eye matches the mask specified by the spec.