What actually happens when you plug in a USB device? (2007)
technovelty.org
technovelty.org
It's pretty amazing that the protocol works in the first place. It's a multi-driver, differential bus with 3 valid states (not including bus arbitration). It does all sorts of dirty things, like in order to identify a device as a USB1.0 or USB1.1 device, a resistor is either applied to D- or D+. In order to determine if the host/device should switch to USB2.0 mode, the host computer will drive both lines to low (SE0) and the device will send high current "chirps" back to the host. Essentially having multiple hosts driving the line at the same time.
Also, when I found that "SetupApi" was The Way you got to USB devices on Windows, I wanted to strangle somebody.
You say this like it's a Windows-specific thing. In Linux, a lot of the USB support is exposed through /sys—pretty much the same idea.
Then all this other stuff happens.
Enumeration is an interesting process -- newly reset devices accept transfers to address zero, until the host assigns a non-zero addres. Then the next device (if their are additional devices detected on a hub, or if the just-enumerated device is a hub with devices below it) can be enumerated (initially responding at 0 after reset), walking the entire tree of hubs and devices (and revisiting it as necessary when hubs report connections and disconnections).
Yeah, it was done after I was asked to run a short course on writing drivers, so the focus was on understanding that sort of layer.
But you want to know how old this is? I actually used the word "palmtop" :)
This sort of form-factor came directly out of things calld "palmtop pc's" like http://en.wikipedia.org/wiki/HP_95LX
A device with a similar form factor but running a mobile OS would have been called a "MID" (mobile internet device) or possibly a tablet - https://en.wikipedia.org/wiki/Nokia_770_Internet_Tablet for example.