Hard Drives
NMI was designed for use with flash/pen drives and card readers. However, hard drives will work if they are properly powered. There are a few issues with hard drives.
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Power Issues. If you have a bus powered hard drive (no dedicated power adapter), you may run into power issues. The USB specification states that USB 2.0 host devices need to be able to provider up to 500mA of power. This is enough for a flash drive. Many hard drives require more to power up (My 2TB WD requires 650mA). While a PC can generally support this spike, not all tablets will. NEVER CONNECT AN UNPOWERED HARD DRIVE TO A PHONE.
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Memory Constraints. Hard drives can contain vast qualties of Photos, Music and Videos. In may cases NMI/NPV will scan the entire drive. This has two problems. One, it's slow. Two, it may cause an out of memory crash. For hard drives, it's recommend to use the "Folders" option on the "Photos" screen, the "Folders" screen for videos and the "Folders" option on the "Music" screen.
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Mac (HFS+) formatted drives. NMI does not support HFS+, so the drive will need to be reformatted.
How do you know if you have a power issue?
If you connect your drive and if it either clicks, starts spinning and then stops, or intermittently prompts you to use the device, you have a power issue.
Power Issue Solutions:
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Charge your tablet to 100%.
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Buy a powered USB hub and put it between the drive and the Nexus. The hubs external power should be enough for the external hard drive. NOTE: You may need to vary the connection order. For me, connecting the drive to the hub, then connecting the hub to the OTG/tablet works best. You may have to vary the order to get the drive working.
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The official Nexus 7 2012 dock by Asus. Allows you to power the device and connect an OTG cable! (Model: 90-XB3XOKDS00020)
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For the Nexus 10, MagNector makes a cable that allows you to charge your device and use the OTG. This should keep the battery charged, but may require the tablet be charged to 100% before connecting the drive.
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Buy a USB "Y" cable for hard drives. Some hard drives come with these. Connect the small end to a power source like a laptop or battery pack. Since OTG only support USB 2.0. Most USB 3.0 drives accept USB 2.0 cables (like your charging cables).
NOTE: Your device charger may or may not power a USB hard drive! Some chargers only support specific devices.
Repairing A Damaged Disk in Windows:
NMI takes preventative measures to ensure that even when disconnected abruptly a drive will be in a valid state. Unfortunately, if disconnected while writing the directory entry it can become corrupted. Windows users, can do the follow to repair a corrupt drive:
- Open Windows Explorer from the Start menu or with {Windows Key}-E
- Right click the drive. Select Properties
- Select the Tools tab
- Click Check Now...
This works for all file systems Windows supports (FAT, NTFS, etc). Alternately, you can type "CHKDSK /F {Drive Letter}:" at the command line.
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