Hi,
On Wed, Jul 02, 2008 at 07:45:25AM -0400, Gregg C Levine wrote:
A USB cable configured to connect two systems together, such as a laptop to receive files from a desktop is simply two USB-A cables wired to an appropriate logic array. This would (Or "should be". Either way) probably be the latest generation in USB Gadget hardware.
Yes. But the logic "array" is quite complex, and implements several layers of protocol. Please look at chapters 5, 8 and 9 in the USB specification for a description of the protocol.
Ideally a Linux system can use this to talk to an appropriately configured system, provided the target was built using the debug features turned on for the USB stack layer.
Not enough. These are the hardware requirements:
* The target USB controller must be EHCI * The target USB controller must implement the optional Debug Port * The target board must have a USB connector for the physical port that supports Debug Port. It is always only one particular port. * The "cable" must implement the Debug Device functional specification. See links on http://coreboot.org/EHCI_Debug_Port
While I have here hardware for trying out this idea, namely my Linux development station, I have not as yet chosen a target.
You will also need the debug device. I suggest ordering the NET20DC product from semiconductorstore.com.
//Peter