Not OP, but for USB "full speed" devices (12 Mbps), you can use a saleae logic analyzer clone ($12) with the opensource pulseview which can decode USB frames and streams rather well.
Even with faster devices, you can usually force them down to 12 Mbps with a USB 1.1 hub for analysis and bugfixing of the driver/firmware, and then have the exact same code work fast without the hub.
On desktop, wireshark also has the ability to monitor USB data transfers for a software-only approach.
Even with faster devices, you can usually force them down to 12 Mbps with a USB 1.1 hub for analysis and bugfixing of the driver/firmware, and then have the exact same code work fast without the hub.
On desktop, wireshark also has the ability to monitor USB data transfers for a software-only approach.