Jules Richardson wrote: Unfortunately that's not true :-(. USB is a horrible standard, and it's not orthogonal - hosts are hosts, and targets (my word, I can't remember what the official word is) are targets. So, if your device wants to be able to use USB memory sticks, it needs to implement the USB host interface. That means it won't be able to talk to a computer (also a host interface.) If you want to do both, you'll need two interfaces (and strictly speaking two sockets - the flat socket (Type A IIRC) should only be implemented on a host, a target should only have the square Type B socket. It ought to be impossible to get a flat-4 male to flat-4 male USB cable, apart from anything else.) (By 'Flat 4' I mean the 'normal' USB socket people see on their computers. By 'Square', I mean the square one with two bevelled corners that you don't see as often (an awful lot of USB devices having captive cables.) You can probably find a driver chip that will implement both host and target though, or you may need two driver chips. The Philips PDIUSBD12 (again, IIRC that's the correct name) which is the only one I've ever used will only do target mode, IIRC. Firewire is a much nicer standard for this sort of thing, but of course defeats the object because noone makes Firewire memory sticks :-). Anyway, I'd definitely stick to CompactFlash, but make sure you implement a Type-II (IIRC, again!) interface, the physical size of which is slightly chunkier; that allows you to use the Microdrive harddisks as well as Flash cards. (To sort of answer one of your other questions, I regularly use 4GB CompactFlash hard disks in my digital camera - the only downside of them is they are sloooooooow, at least the cheapo ones I use. It used to be the cheapest way to get a 4GB compact flash hard disk was buy an iPod Mini, crack the thing open and steal the hard disk out of it - they use a CFlash disk internally!) Cheers, Tim -- Tim Walls at home in Leeds EMail & MSN: tim.walls at snowgoons.com