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ataradov / usb-sniffer

Low-cost LS/FS/HS USB sniffer with Wireshark interface
BSD 3-Clause "New" or "Revised" License
860 stars 104 forks source link

USB HS not passing all the data from host to device #43

Open sx107 opened 2 months ago

sx107 commented 2 months ago

I am making a USB HS sound card on STM32H750. When I plug it in directly into usb port, everything works, but when I plug it in through the sniffer into the same port, packets are missing. Also, seems like I don't see any isochronous packets in wireshark. What am I doing wrong? The problem occurs even when the sniffer and sound card are plugged into different computers.

ataradov commented 2 months ago

USB sniffer is not entirely transparent, as any intermediate device, it will introduce some signal loss. So, some performance degradation is to be expected. You can improve the situation by using shorter and better quality cables. I would use USB 3.0 cables because they generally have better quality. Many USB2 cables are not even close to meeting the specification requirements. I would especially avoid flexible silicone insulated cables. They are very convenient, but are really bad for signal integrity.

I personally seen improvement with this cable https://www.amazon.com/gp/product/B01GGKYR2O

Also check that the PCB is clean from flux residue, especially on the front-end side. Many no-clean fluxes end up being conductive when not fully activated.

It may also indicate that the design is already marginal and the sniffer brings it over the edge. Check the sniffer with a few commercially available USB HS devices. Does it work in that case?