William Chops" Westfield" wrote:
> Doesn't USB sort-of want to know quite a lot of details about such
> "byte streams" ?
> Total bandwidth, latency vs efficiency, etc, etc...

You have to chose the USB transport method.  In this case I was thinking of
bulk.  That's what I have implemented.  There is no guaranteed bandwidth
when there is high demand on the bus, but unless you have something like a
streaming audio device plugged into the bus you'll get lots of bandwidth.

> Serial certainly had its pains, but it seems like it will be a long
> time before we see the USB equivalent of a Basic Stamp, capable of
> sending info serially to N devices connected to any of its N I/O
> pins...

I'm not sure what you mean by "sending info serially".  Does the Basic Stamp
really have a lot of UARTs on it?

If you're talking about using USB as a byte stream between a host
application and the firmware, then that's already here.  My ReadyBoard-02
(http://www.embedinc.com/products/ready02) comes with exactly that.  There
is a host application that sends and receives bytes just like it would in
the old serial days, and a command processor on the PIC that sends and
receives it's end of the bidirection byte stream.  All the magic including
host user space library, kernel driver, and low level firmware are included.
The example application even has a command for writing to port B.  You
install the software, plug the USB cable into your PC and the ReadyBoard
right out of the box, run TEST_U1EX and the SETB command allows you to cause
port B to be driven to any value.

Adding incremental commands and responses to the host app and the firmware
is easy, and no different than it would be if a serial connection was used.
One big difference is that you don't have to specify a COM port.  The
library only talks to compatible devices no matter what else is plugged into
the USB.  It's a lot more "just works" than serial ever was.


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