USB
Here's what I've discovered about some kinds of USB device:
- Keyboard and mouse: they support a simplified bootstrap
mode that's very simple to deal with. Here's a driver for the common
parts of bootstrap-mode keyboard and mouse:
USBHID : USBDevice () USBHID init: devicename [ super init: (OFW open: devicename). self setConfiguration: 1. self setBootstrapProtocol. ] USBHID setBootstrapProtocol [ self controlSetIndex: 0 value: 0 requestType: (DR_HIDD bitOr: DR_OUT) request: SET_PROTOCOL ] USBHID setIdle: ms [ self controlSetIndex: 0 value: (ms // 4 << 8) requestType: (DR_HIDD bitOr: DR_OUT) request: SET_IDLE ] USBHID selftest [ self init. 1000 timesRepeat: [ self readReport ifNotNilDo: [ :e | e println]. ] ] and here's a subclass that knows how to turn the reports into mouse events:
USBMouse : USBHID () USBMouse init [ self init: '/mouse' ] USBMouse init: device [ super init: device. self setIdle: 0 ] USBMouse readReport [ ^MouseEvent fromUSB: (self intrIn: 1) ] MouseEvent fromUSB: report [ self := self new. left := (report first bitAnd: 1) ~~ 0. right := (report first bitAnd: 2) ~~ 0. dx := report second. dy := report third. "Treat bit 8 as sign." (dx bitAnd: 0x80) ~~ 0 ifTrue: [ dx := dx - 256 ]. (dy bitAnd: 0x80) ~~ 0 ifTrue: [ dy := dy - 256 ]. ] The keyboard is similar: it reports the set of keys (identified by scancode) that are currently pressed, and uses a fixed mapping from scancodes onto key identifiers.
I regret that I haven't come back to look at the full-blown USB Human Input Device protocol yet! - Ethernet: In theory the USB
Communications Device Class specifies the high-level interface for
ethernet-like network adapters, but in practice most
USB-ethernet dongles seem to be built from an ASIX
USB-ethernet chip. For example, the Apple USB-ethernet dongle is
internally an ASIX 88772A.
ASIX chips aren't compatible with the USB CDC standard, they use their own custom protocol instead. The protocol is simple but it's lower-level than CDC: you're sometimes peeking and poking registers instead of exchanging messages. - Display: My previous posts ( first, second) describe the USB-VGA adapter I found. I'm unhappy with this device: taking a notoriously closed graphics chip and blindly bridging its PCI bus onto USB is really kludgy. The components don't even seem to be particularly cheap (Octopart suggests $15 for the USB-PCI bridge chip) so I suppose the intention was to save development money by not having to program the dongle. I'd be happier if they'd spent the same money on an ARM- or FPGA- based dongle and programmed it to do the job gracefully, but that's me being a naive software guy.