Battery Charging

Harald Welte laforge at
Fri Apr 13 06:56:28 CEST 2007

On Mon, Apr 09, 2007 at 09:50:15PM -0400, Richard A. Smith wrote:
> I think I finally have our batteries charging.
> Turns out it was an upstream problem with our powered hub.  None of us 
> understood that a powered hub (or at least the powered hub we were 
> using) had to have an upstream root hub to enable the power on the ports.

well, to my understanding of usb power distribution (whcih might be
incomplete, too), this still doesn't explain your behaviour completely.

Usually, drawing up to 100mA is permitted as soon as any kind of
electrical connection is present between neo and upstream hub.  

all hubs _should_ implement overcurrent protection, i.e. switch off
ports if there is a too high current drow from a downstream device.

some hubs implement power switching where the host can switch on/off
power on either all (or any port individually, or certain groups) by
issuing configuration requests.  Even in that case, it was my
understanding, that they always provide 5V/100mA on each of their
downstream ports.

> I've had the units plugged in for about 8 hours and they actually turned 
> on with a battery in them.  Thats the first time we have them booted 
> without the battery connections being hooked up to a lab supply.  Thats 
> going to make it so much easier to work on.


> I see that wen the kernel booted it printed a method about enabling fast 
> charge so hopefully tomorrow I will have fully charged units.

yes :)

- Harald Welte <laforge at>         
Software for the world's first truly open Free Software mobile phone

More information about the neo1973-hardware mailing list