From a quick price-check on ebay,
- Passive (bus-powered) USB Hubs - ~ $2-$5
- Powered (externally) USB Hubs - ~ $15-$20
My use-case is to expand the no. of USB ports on a ARM-based SBC, and to embed the hub in the same enclosure, so I was wondering, if it is possible to just add a regulated (7805 based) wall-wart power adapter, to supply extra current to the devices.
- Is there some per-port and up-stream protection circuit required ?
- Does it make a difference if the host-port is USB1.0 / USB1.1 / USB2.0 (from the point of view of converting the hub to a powered one) ?
- Are there some gotcha's with this approach, which I might be missing ?
BTW, if someone is aware of an existing "embeddable" USB hub circuit schematic, which isn't more expensive (BOM-wise) than the ebay consumer devices, would appreciate a pointer.