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I want to connect a power-hungry external drive to my Raspberry Pi 3. Normally this would mean separate external power supplies for the Pi and the external drive, or else plugging both the drive and the Pi into a powered USB hub. The first option has the disadvantage of using up two power sockets with separate wall warts; the second has the disadvantage that it requires an extra piece of equipment that takes up space and adds to the clutter on my table.

I am therefore considering an externally powered drive that features an integrated USB hub. For example, the Samsung Backup Plus Hub, which gets its power from a wall wart, has an "upstream" micro USB connector on the back and two powered USB connectors on the front. Is it possible to connect this device (or a similar one) to my Pi such that it provides both power and data? If so, do I need to run two separate cables from the drive to the Pi (one from the "upstream" micro USB port on the back and one from the standard USB port on the front)?

  • Advice: If you really want to power your Pi 3 completely you need a usb type C version 3 port. This port can provide 5v @5 amp. It is supposed to also have 20v available, but manufacturers may not enable this. Notice can is highlighted because not every manufacturer follow the specs and allow the full 5A to be available. The trick is out of the dozens->hundreds of type C choices you need to find one that fully honors the specs. Once found you that, then need a type C to the USB port on the Pi. Or get a type C, and cut one end off and DIY it to the Pi 3 power plug. – cybernard Jan 15 '18 at 18:27
  • Did you try this in the end? I bought this drive and then realized this option would make for a good use for those extra USB ports. So far I haven't tried it yet, as the drive came with a US plug and I need an adapter for European outlets but I guess it should work. – Giszmo Oct 23 '18 at 21:23
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You're facing two issues:

  1. The RPi 3 running off of a proper 2.4A power supply can provide up to 1.2A to the combined USB ports. If your power-hungry drive requires more, you're going to have issues powering it directly off the RPi USB ports.
  2. The RPi 3 itself requires more amperage than a USB-standard port provides. Products vary widely, but even USB 3 provides only 0.9A on standard ports, or 1.5A on charge ports. In your case, make sure the hub provides sufficient combined power for both the drive and RPi concurrently. Non-standard hubs may provide more, but not necessarily to multiple ports concurrently.

Unfortunately, this usually leaves you with the answer of "it depends" or "maybe". I don't see anything on the Samsung product page that makes me think it provides adequate power, although I certainly haven't reviewed the unit. I have some USB hubs with charge ports that power a RPi 3 with no problem, and no low-power bolt indicator. Others fail miserably. Your choice of conductors will also matter. Try to use robust USB cables (20AWG or better).

  • I'm not sure how your first point is relevant, since I said that I'm not powering the drive from the Pi. Your second point is relevant, but answers less than half of my question (the part about power, but not the parts about data and whether separate cables are necessary). – Psychonaut Jan 15 '18 at 14:56
  • The first point is relevant to your 1st paragraph. If you feel that data connectivity outweighs power concerns, please proceed and disregard my response. – bobstro Jan 15 '18 at 16:21

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