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Why it's not possible to use USB OTG? [answered]

asked 2013-12-12 00:39:59 +0200

dez gravatar image

updated 2013-12-29 14:06:39 +0200

LaruX gravatar image

I want to plug external hard drive to my Jolla phone. Is it possible?

EDIT: In one answer it was said that OTG is not possible, but reasons were not told. So, what are reasons?

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The question has been closed for the following reason "the question is answered, an answer was accepted" by gabriel
close date 2014-06-01 14:39:18.032961



The SOC itself is able to handle USB OTG mode. The rest of the device is not . Its not providing any power to the upstreamport (as far as i know.) This probably is a hw issue which cant be fixxed but worked around, using a powered usb hub. We had the same problem with the galaxyS1 back in the days.

elyos ( 2014-01-28 03:20:55 +0200 )edit

OTG USB is a feature that needs to be in the next Jolla phone:)

richardski ( 2014-03-26 18:01:44 +0200 )edit

This would have been great to have because I need it to upload tracks to my multicopter/drone. Now I have to look for a new Android device because my old Galaxy Tab P1000 tablet doesn't support it either.

Wizah ( 2014-05-29 21:57:35 +0200 )edit

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answered 2013-12-17 10:03:51 +0200

yunta gravatar image

updated 2014-08-27 11:29:00 +0200

tbr gravatar image

USB OTG is impossible. (ID pin not connected, no way to power the Vusb line)

But, USB host may be possible:

  • given you have external 5V source, and special cable to use it. Voltage booster in TOH would work only for low power devices and would still hit battery hard.
  • circuitry on D+/D- seems to be OK for host mode
  • kernel USB subsystem requires careful selective disabling of the USB-OTG state machine and exposing a device / host mode switch through sysfs. (@phdeswer and @tbr looked into it, but needs more thinking/work due to complex state machine and possible HW-dependencies)
  • you'll need kernel modules for your USB devices obviously, and appropriate system support (like: USB keyboard may not work sanely without maliit support)
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So basically this would need just a powered USB hub... (as ext hw)

kimmoli ( 2013-12-24 23:08:06 +0200 )edit

Would be cool to have all this covered by some other half ;-).

Nux ( 2013-12-26 01:34:45 +0200 )edit

Why USB-OTG is not possible? We have a lot of people here who would like to see explanation what is the problem? Connector? Circuitry? Code?

LaruX ( 2013-12-26 14:20:22 +0200 )edit

why there would be the need for all USB devices if the Jolla has power out to the TOH? An USB keyboard for example should be fine without an external power. That would drain the battery quicker, anyway I'd not use Jolla that way, but Jolla should be able to support that small current drain. ( 2014-01-30 15:48:42 +0200 )edit

would Rj45 - micro usb connection work if OTG was functioning?

Jones14 ( 2014-04-04 19:35:24 +0200 )edit

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Asked: 2013-12-12 00:39:59 +0200

Seen: 5,024 times

Last updated: Aug 27 '14