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Author Topic: USB battery charge class  (Read 464 times)
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anotherandrew
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« on: August 07, 2016, 02:12:52 02:12 »

I understand that newer devices (STM32L series) have hardware support for requirements for battery charge class.

Has anyone made similar with older (STM32F series) devices? It need to be done in software since no hardware support for such things.

Battery Charge Class is not a normal USB class (such as HID or CDC or such) as it is only about bais the D+/D- pins accordingly

Thanks in advancement.
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Gallymimu
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« Reply #1 on: August 07, 2016, 04:13:30 04:13 »

It's really a misnomer to call it a CLASS as it isn't related to the USB protocol at all.  Most of the charging specs out there are extensions or violations of the USB spec.

A DCP dedicated charging port is a short between the data pins (not something you can do with a microprocessor without extra or dedicated hardware.

The other protocols are 1.2V on both (think this was Toshiba) and then there were several apple protocols.

It was something like: 2.2/2.7 for up to 1.5A 2.7/2.2 for up to 2A and then 2.7/2.7 for 2.4A  (again I might be mangling this but you get the idea).

Those voltages would have to be set with a DAC or voltage divider.

You can DIY with with FETS, SSRs, and voltage dividers, but there are some tricks to detection with respect to timing and monitoring current draw.

TI for instance makes some pretty cheap little chips to do DCP and the extensions for you
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frnando
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« Reply #2 on: August 08, 2016, 02:09:21 02:09 »

Maybe you're talking about the "Quick Charge 2.0" (& 3.0) protocol, that uses USB protocol to quick charge new smartphones.
It negotiates with host (via USB) to raise USB power voltage to 9V, 12V and 20V.
Using the same current limit and a higher voltage it transfers four times more power.
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anotherandrew
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« Reply #3 on: August 08, 2016, 04:12:53 04:12 »

@gallymimu yes, thank you. I see the various scenarios in the BCP profile spec doc like you describe. I am think that I can emulate this with external part and sw, did not see particular reason why it need dedicated hw. You seem to agree as well. I will look at dedicate hw too from TI like you mention.

@frnando I did not see quick charge protocol, will research now. this requires special hub or port to supply higher than 5V but might be nice to have as extra option
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Gallymimu
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« Reply #4 on: August 09, 2016, 06:24:04 18:24 »

Maybe you're talking about the "Quick Charge 2.0" (& 3.0) protocol, that uses USB protocol to quick charge new smartphones.
It negotiates with host (via USB) to raise USB power voltage to 9V, 12V and 20V.
Using the same current limit and a higher voltage it transfers four times more power.


Quick charge isn't part of the USB spec.  It's a bastard protocol pushed by qualcom.  It uses the same kind of scheme (odd voltages on the data lines) to indicate charging levels.  It isn't "communicated" over USB per se.  See here for a interface description http://www.mouser.com/ds/2/328/chiphy_family_datasheet-269468.pdf. I'd not pursue development here as it's going to go away.  Quick Charge was really a stop gap to the USB power delivery spec that we are seeing partially implemented in some USB C devices.  The power delivery spec is an official spec and defines power delivery for up to 100W.  That said quick charge might be following the PD spec but I'm not certain (haven't researched it and haven't found interface specs for quick charge publicly available).

Posted on: August 09, 2016, 06:22:05 18:22 - Automerged

@anotherandrew, yes I am in agreement with you totally manageable with your own design, but possibly not worth it depending if you are developing a product or just doing it for your own edification.
« Last Edit: August 09, 2016, 06:33:35 18:33 by Gallymimu » Logged
CocaCola
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« Reply #5 on: August 09, 2016, 07:27:12 19:27 »

Quick charge isn't part of the USB spec.  It's a bastard protocol pushed by qualcom.

I have hated the fact that many hardware manufactured 'decided' that USB was an all purpose charging and power port, and ever since the early days have attempted to milk excess power over and above the USB spec from the ports causing problems for the consumer since most PC manufactures built to spec...
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Gallymimu
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« Reply #6 on: August 10, 2016, 06:05:26 06:05 »

I have hated the fact that many hardware manufactured 'decided' that USB was an all purpose charging and power port, and ever since the early days have attempted to milk excess power over and above the USB spec from the ports causing problems for the consumer since most PC manufactures built to spec...

Agreed, it's turned into a real mess.  What pisses me off is that Qualcom pulled this quickcharge crap AFTER the USB power deliver spec was ratified!!  It's just made things worse and more incompatible.
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