CDC ACM
From Openmoko
USB CDC (Communications Device Class) ACM (Abstract Control Model) is a vendor-independent publicly documented protocol that can be used for emulating serial ports over USB.
CDC ACM is used to access the U-boot bootloader prompt over USB (see: U-boot#Using_usbtty_from_Linux).
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Hardware specifics
Neo1973 and CDC ACM
The Neo1973 u-boot boot loader contains support for obtaining the boot loader prompt over USB CDC ACM.
The Openmoko kernel also contains CDC ACM device support, contained in the g_serial.ko kernel module.
Host PC and CDC ACM
Linux
Linux has a generic CDC ACM host-side implementation in the kernel module cdc_acm.ko
On 2.6.25 this is at "Device Drivers -> USB support (USB_SUPPORT [=y]) -> Support for Host-side USB (USB [=m]) -> USB Modem (CDC ACM) support (USB_ACM)"
Windows
FIXME
MacOS X
See the USB Serial section in the MacOS X article.
Specification
http://www.usb.org/developers/devclass_docs/usbcdc11.pdf (3.6.2.1)
See http://wiki.openmoko.org/wiki/USB_CDC_ACM from more information
