alt Hacker NewsAges ago when I was trying to create a simple USB device, I found that there is very much zero information how to do it - e.g. how to correctly write descriptors and so on. The typical advice was: find similar device to what you want to make, copy its descriptors and adapt to your own device using trial and error.
Sounds like USB is a wonderful standard. Am I wrong?
Replies
15155 • today at 8:42 AM
USB is nice, but electrically some parts of USB 1/2 are kind of complicated (not true differential signaling.)
pjc50 • today at 9:13 AM
Eh, there's very little tutorial content, but as far as big corporate standards go it's fairly reasonable. There is a downside to "too much choice", in that you have to read a lot to find the most relevant pre-defined type of device to what you're doing.
Descriptors also were kind of a mystery for me until I realized that they're just a binary structure with a fixed format that the host reads and interprets.
The device descriptor is easy enough to get right as it doesn't have too many fields and every USB class just defines in the specification which Class and SubClass it uses for its interface descriptor as well as which endpoints that interface needs to have. And that's, for the most part, all you need for the host to recognize your device