Next time I suggest you use your web browser and do a bit of research first= .. http://compliance.usb.org/index.asp?UpdateFile=3DBattery%20Charging&Form= at=3DStandard What you needed to look for on the web was "USB-IF charging spec" to find i= t. It took me about 20 minutes to find it because I had to search using th= e right question. There are also numerous posts in their forums under https= ://www.usb.org/phpbb/viewforum.php?f=3D1 . I might be USB clueless but I fo= und out where to look, with a little foot work. I knew about usb.org so I s= earched using there internal search. From there (me being lazy) I used the = search "USB-IF charging spec" after reading a few posts (which used that ph= rase) and found the above link. = Essentially it says you need to do certain things to allow charging from th= e USB port. You should always use what the USB.org says for compliance with= the charging spec.. That means you may not draw more than 5 units (0.5A) f= rom the USB port OR that port will be turned off automatically. The USB cab= le wire can't handle that much current even though it looks like USB 3 will= have 'bigger' specs. I've noticed lots of cheats (the parallel plug trick)= . I personally think that is likely to get there device USB compliance revo= ked eventually. USB is a complicated bus, so I suggest you be sure your ch= arger draws exactly what it needs to (< 0.5A) and never more. The power is current limited through a sense FET device (I know this becaus= e I've been looking at power switches and they all said USB that could hand= le .5A hmmm suspicious huh?) In any case these will shut off power if you e= xceed 0.7A, add in line drop you really can't draw more than 0.5A from the = bus without the power going bad on you. Stephen --- On Tue, 12/1/09, YES NOPE9 wrote: > From: YES NOPE9 > Subject: [EE] Mystery of USB battery charger > To: "Microcontroller discussion list - Public." > Date: Tuesday, December 1, 2009, 3:50 PM > My Blackberry 9530 Storm ( which is > the worst cell phone I have ever=A0 = > owned ) will charge it's battery via the USB port when I > use a=A0 = > Kensington power adapter which has a USB port.=A0 The BB > will also=A0 = > charge with it's supplied USB charger. > = > I built my own USB power adapter which supplies=A0 5V to > the correct=A0 = > pins.=A0 The Blackberry does not charge.=A0 The only > difference I can=A0 = > imagine is that the data + and - lines make some > difference.=A0 My=A0 = > adapter leaves these lines unconnected.=A0 I don't know > what the=A0 = > Kensington does.=A0 I have measured the 5V and it looks > okay when loaded. > = > Any ideas ? > = > Gus > -- = > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > = = -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist