> I noticed that USB OTG is working its way down into some pretty small
> and inexpensive PIC chips, and I'm wondering just what it means.  USB
> host has always implied a certain amount of complexity, and a certain
> abundance of compute resources, neither of which would be true for a
> PIC18-class thing with 32K of program space.

The smallest ones are 28 pin PIC24 chips ...

> What can you expect a small USB host to be able to talk to?
> USB Flash drives?  Yeah, it looks like there is an App-note for
> that.   Terrabyte disks ?  (Mind boggling!)

Yes - if it is on a USB interface using the standard MSD interface ...

> USB Bluetooth interfaces?  For what kinds of profiles?  THat'd be
> pretty neat, since the cheapest bluetooth interfaces for generic
> things like serial, are much more expensive than the cheap USB BT
> dongles plus the small PICs I'm talking about!

There is no code for a Bluetooth stack, largely because most of the 'cheap' 
BT devices do most of the handling in PC software, and ones which handle the 
BT stack onboard are expensive, but there is a thread on the Microchip forum 
where a guy seems to claim to have done a stack for a specific BT device, 
and have it talking to a PC. See 
http://www.microchip.com/forums/tm.aspx?m=489233 for details.

> USB Wireless network interfaces (802.11abgn)?  Ditto on the cost
> paradoxes.


Same problem as BT interfaces.

> Non-wireless interfaces?

If it uses a standard USB device interface then code can be written for it. 
People do have problems connecting many of the USB-Serial chips as many of 
these use their own driver in windows instead of the CDC driver supplied.

> Mice, keyboards?  Hubs? (or does "OTG" imply a single device is
> connected?)

Hubs are currently not supported in the Microchip code, but people with 
suitable knowledge have written code to use hubs. I believe that Microchip 
are investigating adding hub code to their stack. Otherwise HID, MSD, CDC 
are all supported for single devices.

>
> Has anyone started playing with host-side USB programming with PICs?

I haven't yet, only as a device. 

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