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piggyback power off the cell phone?
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piggyback power off the cell phone?

by _E_NL on Mon Jul 15, 2019 7:09 pm

does anyone know if it's possible to power a CPX using the USB jack on a cell phone?

I have a little project that would work best if the CPX could be something of a cell dongle.

_E_NL
 
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Re: piggyback power off the cell phone?

by _E_NL on Tue Jul 23, 2019 2:27 pm

UPDATE
Solved my own question: YES this is possible using an OTG cable: I snagged a 0.65' USB C <=> Micro USB on Amazon for <$5, and it works great.

The only problem now is that it's a bit more cord than I want, making it a little unwieldy, and I don't like putting strain on the notoriously (in general, not the CPX specifically) brittle micro USB.

A flatter 180° link would be ideal, and a really handy way to power projects since most of us already have cell phones... where do I make product suggestions / requests?

_E_NL
 
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Re: piggyback power off the cell phone?

by OliVDB5590 on Thu Jul 25, 2019 9:22 am

Great, thanks, it's uncommon but always welcome to see people who had trouble on forums giving updates once the problem's solved.
So, if I got you right, it'd be ideal to have a short cord, so that you can put it on a table or something comparable without putting too much strain on the inlets?

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Re: piggyback power off the cell phone?

by _E_NL on Thu Jul 25, 2019 1:58 pm

OliVDB5590 wrote:So, if I got you right, it'd be ideal to have a short cord, so that you can put it on a table or something comparable without putting too much strain on the inlets?

more like a HAT for a cell phone; something that could attach to a case. reducing strain would definitely be a priority.

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Re: piggyback power off the cell phone?

by adafruit_support_mike on Sun Jul 28, 2019 2:26 pm

It depends on the cell phone.

USB-OTG can power external devices, but plain USB can’t. They both use the same micro-B connector though, so it’s hard to tell them apart visually.

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Re: piggyback power off the cell phone?

by _E_NL on Mon Aug 05, 2019 1:47 pm

adafruit_support_mike wrote:They both use the same micro-B connector though, so it’s hard to tell them apart visually.


do you know if that's true for USB C as well?

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Re: piggyback power off the cell phone?

by adafruit_support_mike on Tue Aug 06, 2019 9:05 pm

USB-C is even worse.

The official line is that USB-C "enables many technologies while mandating few". It allows for 'alternate modes' that are mutually incompatible and can only be distinguished by the markings printed on the terminators. All USB-C cables have to contain an IC that identifies the cable's function, and obeys the USB Power Delivery Protocol. The protocol allows a client device to negotiate its power requirements with the USB host, but requires a data connection. Without negotiation, the USB host is only required to supply 100mA.

A RasPi's power jack doesn't have a data connection. It just relies on a USB-2 cable's ability to carry at least 500mA, and the fact that most recent cables can carry a couple of Amps.

USB-C cables are required to carry a minimum of 3A, and those that support the high-power option have to carry 5A. The amount of current you can actually get without a data connection is unclear.

And those are only issues related to the spec. There are already companies known to have made cables that aren't compliant, a few of which have been miswired badly enough to damage devices connected with them.

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