So what I'm trying to achieve is a charger that can be connected to a USB port from a PC for example, then it will charge a 3,7V 2000mAh Lithium Ion Battery with configurable 250mA-500mA current (set by a resistor on the PCB for MCP73831T).
Then the charger can be connected to a smart phone eg. N900 and it will supply it with 500mA.
The charger itself would have 2 different USB ports, one to charge itself (micro-B) and one that would allow devices to be charged from it (Type A) so basically I could flip the same charging cable around to charge my phone or eBook etc. device that has micro-B on it.
I'm having a few doubts though of making this work:
I've understood that for a device to draw over 100mA from USB it needs to be allowed to do so?
So I couldn't just hook the charger to my PC's USB port with D+ and D- floating and expect it to get 400-500mA of current from it?
And also for charging a device from the charger:
I've also read that some devices won't even charge from a USB that has D- and D+ floating, is this correct and how can this be fixed?
I'd remember a jumper of some kind between the lines.
If you have got any feedback about this I'd love hear it.
All help is respected![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Thanks!
Then the charger can be connected to a smart phone eg. N900 and it will supply it with 500mA.
The charger itself would have 2 different USB ports, one to charge itself (micro-B) and one that would allow devices to be charged from it (Type A) so basically I could flip the same charging cable around to charge my phone or eBook etc. device that has micro-B on it.
I'm having a few doubts though of making this work:
I've understood that for a device to draw over 100mA from USB it needs to be allowed to do so?
So I couldn't just hook the charger to my PC's USB port with D+ and D- floating and expect it to get 400-500mA of current from it?
And also for charging a device from the charger:
I've also read that some devices won't even charge from a USB that has D- and D+ floating, is this correct and how can this be fixed?
I'd remember a jumper of some kind between the lines.
If you have got any feedback about this I'd love hear it.
All help is respected
Thanks!