![]() When accurate timing matters, USB capture devices also allow you to use a separate computer to capture and display the data, so you’re observing the accurate timing without placing additional burden on the PC acting as the USB host.Īdmittedly, these are pretty niche usage cases. Some of them offer digital input signals which can be captured alongside the USB communication. USB capture devices usually provide precise time stamps on every captured token. Other fine details, like the number of NAK tokens or whether a high speed device replies with ACK or NYET token are also handled automatically by PC hardware and generally not visible to software on your PC. For example, when communicating with a 12 Mbit/sec USB device which is plugged into a USB hub, you can’t observe the split-start and split-complete tokens exchanged between your PC and the hub. ![]() USB capture with your PC’s hardware also can’t show you finer details of the actual USB communication, which are handled automatically in the USB host controller hardware on your PC. They wires simply don’t connect to your PC, unless you use dedicated USB capture hardware. You also can’t observe communication such as between an Apple iPad and a SD card using the camera connection kit. For example, when I wrote the USBHost_t36 library for Teensy 3.6 and 4.1, I leaned heavily on a Total Phase Beagle 480 analyzer to see what communication was actually happening between Teensy and USB device, or USB hubs and then downstream devices. USB capture on your PC is usually good enough for the common uses of reverse engineering USB devices or troubleshooting code running on a USB device microcontroller.īut Wireshark using your PC’s USB port can’t help if the communication is between a USB device and some USB host other that your PC. Posted in Misc Hacks Tagged usb Post navigation Meanwhile, if you’re whipping up your own useful debug tools, don’t hesitate to drop us a line! We’ve seen some other similar hardware before. Once assembled, you can program the chips via USB, with no external hardware programmer required. Gerber files are available and the required components can be bought off the shelf. If you need this tool, spinning up your own is straightforward. In addition to live sniffing, it also allows captured data to be saved for later analysis. Most commonly used for network packet sniffing, Wireshark can also be used with a wide variety of other capture hardware for other debugging tasks, as seen here. The device is built specifically for use with Wireshark. This setup is capable of operating at data rates of up to 40-50 MB/s, more than enough to debug the vast majority of USB peripherals on the market. To sniff high-speed USB communications, the device relies on a Lattice LCMXO2 FPGA and a Cypress CY7C68013A microcontroller, paired with a Microchip USB3343 USB PHY. ![]() Sometimes, it’s the only way to properly understand what’s going on. ![]() If you’ve done any development on USB hardware, you’ve probably wished you could peek at the bits and bytes as they pass through the data lines. ![]()
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