Hi,
Can it be that you did not follow USB recommendation in regards of characteristic line impedance, termination and so on.
You need careful design to ensure signal integrity.
Klaus
For a serious assess of design problems, I would expect a readable layout print along with a schematic.
I agree that connecting two USB jacks in parallel doesn't promise correct operation. Neither wiring USB on a two layer board without regarding trace impedances.
I'm inclined to agree with Klaus, when dealing with faster USB interfaces there are two critical factors, the line impedance (which comes down to trace width and separation) and differences in the + and - data line lengths. Being differential, if you can keep the traces parallel and following the same route, they should have good immunity from interference.
Brian.
You can have impedance matched USB traces on 2-layer board if necessary.
I would like to understand the implemented circuit topology, also the involved USB speed. Using full speed (12 MBps) or high speed (480 MBps) makes a big difference. For high speed, there's no way to bypass matched trace impedances and strict point-to-point wiring.
You should not ignore the ground integrity, that's one point
that's common between the outside world, the USB and all
the digital logic. I don't see a robust ground plane, rather a
spindly-looking ground trace connecting various points. If
the ground is weak then the shield may become a signal,
unable to resist common mode coupling or even maintain
a Z=50 impedance (add significant inductance, for edges
to bounce off of).
An automatic signal switch for the D+ and D- lines may be possible. We are still missing most application details.However like i mentioned i don't want to bother the user with a switch if possible. Is there is a neat way to do this?
Apparently invisible in the layout screenshots. Need readable layout print, as already mentioned.I run a ground plane on one side of the pcb, vcc on the other side.
An automatic signal switch for the D+ and D- lines may be possible. We are still missing most application details.
Apparently invisible in the layout screenshots. Need readable layout print, as already mentioned.
Maybe true, maybe not.I'll redesign the pcb though so not much point on reviewing this one.
Hi,
Maybe true, maybe not.
We just see the information you give...and it makes me assume that you are not used to design differential traces with known line impedance.
Your traces are close to the PCB edge, thus you might get unsymmetrical impedances.
I recommend to post your actual design .... it won't hurt ... but it enables us to verify it.
Klaus
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