I want to learn writing device drivers for USB devices (on linux kernel or microcontrollers, if that matters). Hence, I am looking for sample USB development kit.
e.g. when I wanted to learn I2C, I could find hundreds of I2C based sensors, LCDs, switches, etc. Now I am looking for similar simple beginner level USB devices that can be used to learn USB driver programming. It could be a small thumb-drive shaped circuit board with LEDs and buttons, that I can blink or receive button press events over the usb.
Can someone please point me to such device or kits, if they exist. I searched a lot but always ended up with wrong search results, probably I need more fine-tuned search keywords. I do not want to begin with a USB mouse or USB keyboard to learn USB driver programming. I would love it to be simple to begin with.
EDIT I am just adding the examples here which I found, it may help someone in future. However, I am looking for kits intended for USB development that are developer friendly (with documentation). The devices below are not.
Consider this example : https://www.linuxjournal.com/article/7353 (a USB based LED lamp). I am looking for such kind of devices.
Another example : here is another article which makes of similar device : http://matthias.vallentin.net/blog/2007/04/writing-a-linux-kernel-driver-for-an-unknown-usb-device/