![]() ![]() Important here is to set at least 100 MHz sampling, so if your analyzer does not support it, it might not work for you despite USB being 48 MHz. There is nothing special here, but just in case, this is how my configuration looks like: DSView options And main window I guess adding some resistor could decrease required length, but cables alone works too, so why bother? DSViewĪs we now know how and why should we connect our devices, we can go on to next part, which is DSView. So we need cable that is bad enough to stop working as USB 2.0, but good enough to maintain full-speed USB transmission □ That is how I did it. This ancient standard used 3V3 logic for communications. So why this ugly three part cable is better? The trick is to force USB controller to downgrade to USB version 1. From what I was able to observe with oscilloscope you would need to set threshold at around 0.25V, while DSView allows you to set it to either 0.2V, or 0.3V. USB 2.0 is low voltage protocol, so it barely touches 0.5V. ![]() With USB 2.0 I was not able to decode any traffic with DSView. But problem is with DSView program, or capabilities of hardware. Otherwise you are going to have degraded performance due to transmission problems. In theory the shorter the cable, the better. You think that this would work? Reality is that this is what you need 4 wires and 2 USB-A connectors at both ends. This might sound like a simple task, but I am going to show that it is not necessarily is. Then a bit of exporting and you get pcap file for wireshark. ![]() Fortunately I have DSLogic logic analyzer, that could easily record such a slow protocol as USB. So definitely I needed another way around this problem. As is usual with this kind of devices there is no SDK available and compiling custom kernel module for such system, while has huge educational value, is most likely going to end up with failure. The traffic that I wanted to sniff was between router and modem that connects to it via USB. Direct reason for such a long break was being stuck at attempts in using usbmon to capture USB traffic. Lately I came back to reverse engineering project that I started few years ago. ![]()
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