How to Store 2 Bytes of Data in Your USB Mouse (Yes, Really)

Sometimes the best weekend projects start with the dumbest questions. Mine was: "Can I use my mouse as a storage device?" Not like plugging in a flash drive — I mean actually writing arbitrary data into the mouse's onboard memory and reading it back later. Turns out, you can. Sort of. Let me walk you through how HID feature reports work, why your mouse has writable memory you never knew about, and how I managed to stash a whopping 2 bytes of data in a peripheral. The Problem: HID Devices Have Hidden Depth Most developers interact with USB mice through high-level abstractions. The OS handles everything — cursor movement, button clicks, scroll events. But underneath, your mouse speaks a protocol called HID (Human Interface Device) , and that protocol supports more than just input reports. HID defines three types of reports: Input Reports — device → host (mouse movements, clicks) Output Reports — host → device (think keyboard LEDs) Feature Reports — bidirectional, used for device configur