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I have a small custom 5V 2mA device which is powered over USB. To be specific, it will be powered over USB by connecting it to an Android smartphone or an iPhone. There is no data transfer. I currently use an OTG Type A connector (i.e., shorting the ID and GND pins on the phone), but a non-OTG connector (i.e., floating the ID pin) also successfully delivers power from my particular phone.

Are there any phones out there which would give me power for an OTG connection, but give no power for a non-OTG connection? My understanding of the USB specification is that this is allowed (and maybe even preferred to preserve the phone battery), but I'm simply hoping it does not happen.

The above question was intended for phones with micro-USB Type A ports (since I'm really not sure what a Type C OTG cable would be). So, to also cover the latest technology, are there any current phones with Type C ports where the resistance on the CC1/CC2 pins changes my power?

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  • \$\begingroup\$ There is no micro-A receptacle defined in USB specifications, there are only micro-A-B receptacle. Could you clarify please? \$\endgroup\$ – Ale..chenski Jan 12 at 1:32
  • \$\begingroup\$ Mentioning USB A connector and iPhone together is an oxymoron \$\endgroup\$ – DoxyLover Jan 12 at 2:14
  • \$\begingroup\$ "resistance on the CC1/CC2 pins changes my power?" Which "my power" do you mean? Power delivered by phone? Or power taking by attached device? \$\endgroup\$ – Ale..chenski Jan 12 at 19:44
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"but a non-OTG connector (i.e., floating the ID pin) also successfully delivers power from my particular phone."

This is odd. An OTG port shouldn't output any power on VBUS unless a "slave" device with ID=GND is plugged in. This is how it is done on majority of Android smartphones. However, in very rare cases when a full-blown OTG is implemented (all these crazy "session control protocols", fishing for role change, etc.), it is possible that VBUS becomes active with a small source of power. If your device is taking just 2 mA, it might be enough for it. But this behavior is very rare on smartphones, most of them will use ID pin status to turn into host mode and activate VBUS output. With ID=floating the port doesn't output any voltage. This should answer your first question,

Are there any phones out there which would give me power for an OTG connection, but give no power for a non-OTG connection?

Regarding the Type-C, it is too broad to answer.

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