Get the Right On-The-Go (OTG) Micro-USB Cables for MiniPCs and Nexus 7 Tablets

This article was adapted from the OakLeaf Systems Blog’s Get the Right On-The-Go (OTG) Micro-USB Cable and Bluetooth Peripherals for Nexus 7 Tablets of 1/12/2013.

Contents:

 
Update 1/12/2013: Added a Verifying Compatibility of USB and Bluetooth Peripherals for the UG007 Android 4.1 MiniPC Device section.
Update 12/22/2012: I’ve tested the two low-cost USB-2 (Type A) to Micro-USB (Type B) converter cables discussed in this post and verified that they are OTG-compliant.

Introduction

imageI (@rogerjenn) purchased a 32-GB Nexus 7 tablet when Google made them generally available in late June 2012. My interest in the product stemmed from the desire to gain familiarity with the Android operating system without the need to enter into an extended cellphone contract (my wife and I are Verizon feature-phone customers with LG VX8360s on a low-cost plan) or pay a premium for an unlocked Android cellphone.

image_thumbUpdate 12/20/2012: Brooke Crothers asserted “Google is planning a Nexus 7 that could eventually go as low as $99, an Asia-based report claims” in a deck for his Google planning cheaper Nexus 7, report claims article of 12/19/2012 for CNet News, and noted:

Google and Asus are currently shipping about one million Nexus 7 devices per month, according to recent statements from Asus executives.

imageCurrently, I’m using the Nexus 7 to determine Android tablet compatibility of Office 365 SharePoint Apps with Visual Studio LightSwitch front ends autohosted in Windows Azure, as described in my LightSwitch HTML Client Preview 2: OakLeaf Contoso Survey Application Demo on Office 365 SharePoint Site post.

I was able to fast-charge the Nexus 7 with a D-Link DUB-H7 High Speed USB 2.0 7-Port Hub (powered, US$24.99) and gain access to the Nexus’s internal file system with the short male Type A USB 2.0 to male Micro-USB Type B charging cable:

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Windows 7’s Windows Explorer connected to a Nexus 7 with a USB adapter cable

I later learned from the Reverend Kyle’s [VIDEO] Google Nexus 7 Tablet & OTG Cable for USB Host Connection article of 7/25/2012 on the XDA Developers Forum that the Nexus 7’s Micro-USB connector supported a limited repertoire of host-mode features, including support for USB keyboards and mice:

image

imageI have taken the time to connect an OTG (On The Go) cable into my Nexus 7 tablet to demonstrate for you how to take advantage of the USB Host capabilities of the device. You can plug in USB input devices such as a keyboard or a mouse, or both, with the use of a USB hub. You can also plug in a USB drive for extended data storage, as long as you download a free app from the Play Store called StickMount. Now, StickMount requires that your device is rooted, so if you have not done that yet, please follow my “Idiots Guide to Unlocking & Rooting your Nexus 7″, located here: http://www.youtube.com/watch?v=sK9avekmA1c

Results may vary in terms of what USB devices work and what don’t.

Note: I use HoneySoft’s Nexus Media Importer app (US$2.99) from the Google Play store to enable connecting USB drives and streaming video. This app eliminates the need to root your Nexus 7 and run StickMount.


A Misstep with a Micro-USB to Standard (Type A) USB Adapter

I wanted to try a conventional external keyboard and trackball with the device, so I purchased a male Micro-USB type B to female type A USB 2.0 adapter from my favorite local cable supplier, SFCable.com:

imageSFCable.com item number AD-USBAMCB-FM, $1.95 (plus shipping) – Not OTG-compliant

This was then (and still is) the only such adapter offered by SFCable.com. I wanted to use the adapter to connect an unpowered (passive) four-port USB hub for multiple human input-devices (HIDs):

imageSFCable.com four-port USB hub item number NET-ET-420BG, $8.95 (plus shipping)

When I received the adapter, plugged it into the Nexus 7 hub, the red power LED didn’t glow and the Nexus 7 didn’t recognize the connected keyboard and trackball. Directly connecting the keyboard or trackball didn’t work, either.

Note: Several Nexus 7 users/developers recommend plugging all the USB devices you plan to use in to the hub before plugging the hub in to the Nexus 7. I haven’t found this to be necessary.

Searching for Nexus 7 users with similar experiences led me to uberNoobZA’s The USB OTG [cables] that Do and DO NOT work with Nexus 7 Thread XDADevelopers post of 8/3/2012:

I realize there is another thread about an OTG cable that does work with the Nexus 7, but after 3 or 4 posts, it has digressed into discussing what to plug into the OTG and what to use instead of OTG.

As I struggled to find any confirmation of a device I could buy in the UK that DID work with the Nexus 7, I thought I’d make this thread. At the same time, I also bought a USB OTG adapter that does NOT work with the Nexus 7, so thought I’d let you know of that one too. I would like to request that people use this thread to show USB OTG’s that they have confirmed as working with the Nexus 7 and also those that do not work.

For those OTGs that are working, please indicate what tests you have done as well as where you purchased it (links please). Please try to refrain from discussing / recommending devices to plug into the USB OTG unless it’s to say you have confirmed it as working with the USG OTG and Nexus 7.

DOES work with Nexus 7:

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Micro USB Host Mode On The Go OTG Cable for Nexus 7, Xoom, Galaxy S2, Nokia N810 / N900, Toshiba TG01, Archos G9 by FORPOWER from Amazon.co.uk, £1.69 (plus shipping)

I can confirm that the following work on the Nexus 7 with this Adapter:

  • USB Keyboard plugged into Adapter
  • USB mouse plugged into Adapter
  • USB mouse and USB keyboard plugged into (self powered) USB HUB, and HUB plugged into adapter
  • USB Memory Stick (pendrive as some call them) as long as the Nexus 7 and Google Nexus are ROOTED and have a utility called StickMount installed (from Google Play Store)
  • USB Dongle for Wireless Keyboard (with built in trackball), plugged into Adapter. Nexus 7 picks up both mouse and keyboard

Does NOT work With Nexus 7:
http://www.amazon.co.uk/gp/product/B…ls_o03_s00_i00

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Ex-Pro® On-The-Go OTG USB HOST Cable for Archos Tablet 7 – Micro USB to Standard USB by Ex-Pro, £2.75 (plus shipping)

The above adapter appears similar, but not identical, to the SF Cable item.

All-in-all, I wasted about 2 hours and the cost of the adapter (plus shipping) due to not knowing SF Cable’s adapter wasn’t OTG-compliant. Hopefully, this post will save others similar lost time and expense.


Success with the U.S. Version of the FORPOWER OTG Cable

Following appears to be the equivalent to the FORPOWER cable for shipment from the U.S.:

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EverydaySource Compatible with Google Nexus 7 Tablet Micro USB OTG to USB 2.0 Adapter by EverydaySource, US$1.03 (plus shipping)

The above cable, as well as the similar SANOXY Micro USB Host Mode OTG Cable Flash Drive SD T-Flash Card Adapter FOR Samsung GT-i9100 i9100 Galaxy S II 2 GT-N7000 Galaxy Note by SANOXY ($0.65 plus shipping) work well for me.

Tip: If your connected peripherals don’t work with one of the above adapter cables, you probably need to enable USB Debugging (Settings | Developer Options |  Debugging | USB Debugging) to enable your Nexus 7’s OTG Host mode. You can tell if Host mode is enabled by an illuminated power LED on your USB hub.


Failure with an IVSO® Nexus 7 Tablet Micro USB Host OTG Cable Adapter

By accident, I ordered an IVSO® Nexus 7 Tablet Micro USB Host OTG Cable – Micro USB B/Male to USB2.0 A/Female OTG Host Cable for Nexus 7 (Black) adapter from Amazon.com instead of the above EverydaySource adapter. This device failed as a host controller. From my Nexus 7 USB Host Cable Doesn’t Work with My Nexus 7 review on Amazon.com:

I purchased this short male (supposedly OTG) Micro USB to female USB A connector to simplify connecting as a host to a four-port hub, which connects to my development PC, a keyboard, trackball, and USB disk drive.

However, it doesn’t enable my Nexus 7′s host features – the expected Nexus 7\Internal Storage node doesn’t appear in Windows 7′s Explorer nor does the serial number appear when starting Mark Skippen’s Nexus Toolbox app.

In other words, this cable with a $29.99 list price (!) doesn’t work as advertised and I plan to return it for $5.99 credit.

Other reviewers reported that it worked with a powered hub. However, I need portability, so a powered hub isn’t an option. Powered hubs add to the cost, also.


Divergence from Published Standards for OTG Connectors

Wikipedia’s Universal Serial Bus topic provides the following details about USB OTG connectors and receptacles:

USB On-The-Go Connectors

imageA USB On-The-Go device is required to have one, and only one USB connector: a Micro-AB receptacle. This receptacle is capable of accepting both Micro-A and Micro-B plugs, attached to any of the legal cables and adapters as defined in Micro-USB1.01.

The OTG device with the A-plug inserted is called the A-device and is responsible for powering the USB interface when required and by default assumes the role of host. The OTG device with the B-plug inserted is called the B-device and by default assumes the role of peripheral. An OTG device with no plug inserted defaults to acting as a B-device. If an application on the B-device requires the role of host, then the Host Negotiation Protocol (HNP) is used to temporarily transfer the host role to the B-device.

OTG devices attached either to a peripheral-only B-device or a standard/embedded host will have their role fixed by the cable since in these scenarios it is only possible to attach the cable one way around.

Host interface receptacles

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The Nexus 7 and most other small devices with USB 2.0 that I’ve seen have Micro-B connectors, which theoretically restricts them to a peripheral-only type B device role.

Cable plugs (USB 1.x/2.0)

Cables exist with pairs of plugs:

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Non-standard: Existing for specific proprietary purposes, and not interoperable with USB-IF compliant equipment.

In addition to the above cable assemblies comprising two plugs, an “adapter” cable with a Micro-A plug and a Standard-A receptacle is compliant with USB specifications.[25] Other combinations of connectors are not compliant. … [Emphasis added.]

The above “adapter” cable is what’s required by the specs, but all devices I’ve seen with Micro receptacles are Micro-B, not Micro-A types.

image

Note: Microsoft Surface tablets don’t share these issues because they provide a standard Type A receptacle.


USB Y-Cables for Charging Nexus 7 Devices While Using USB Peripherals

An XDA Developers Nexus 7 OTG + charging is here article of 10/13/2012 by mvmacd reports:

It says it’s only been tested with CM10, but might also work with other ROMs. I finally got my Y cable, and I can confirm it works. [Using this cable from ebay, $6]:

image

Micro USB Host OTG Cable w/USB power S2 i9100 S3 i9300 i9220 i9250 Ships From US (US$9.99 with free shipping)

[Patch details:] http://mehrvarz.github.com/otg-power-nexus7.html

This means you can plug in your flash drive or hard drive and use it while on AC power!

I’m excited about this and I hope devs here can implement this into the Nexus 7 ROMs.

Check this patch to see how to implement into your kernel.

imageNote: Using this Y-cable requires unlocking your Nexus 7’s boot loader and replacing it with one of the two patches. I used Mark Skippen’s (@mskipxda) Asus Google Nexus 7 Toolkit v4.0.0 to unlock the boot loader and perform other operations on my Nexus 7.

I haven’t tested the ability of the above Y-cable to power peripherals, which requires testing it with Timur Mehrvarz’ Nexus 7 boot image that has external power and charging status enabled. I have verified that this cable is OTG-complaint.


Verifying Compatibility of USB and Bluetooth Peripherals for the UG007 Android 4.1 MiniPC Device

I’ve ordered a CozySwan UG007 Android 4.1 MiniPC device from Amazon (sold by VALI and fulfilled by Amazon) for US$69.50 (Prime 3-day freight included) based on James Threw’s The RK3066 Android 4.1 mini PC is the MK802′s younger, smarter, cheaper brother, we go hands on Engaget review of 1/12/2013, which begins as follows:

imageWhen the MK802 Android mini PC landed in our laps, it caused more than a ripple of interest. Since then, a swathe of “pendroids” have found their way to market, and the initial waves have died down. While we were at CES, however, we bumped into the man behind the MK802, and he happened to have a new, updated iteration of the Android mini PC. Best of all, he was kind enough to give us one to spend some time with. The specifications speak for themselves, and this time around we’re looking at a dual-core 1.6GHz Cortex A9, 1GB of RAM, 4GB of built-in flash (and a microSD slot), WiFi in b/g/n flavors, DLNA support and Bluetooth, all running on Android 4.1 Jelly Bean. There’s also a micro-USB, full-size USB, female HDMI port and 3.5mm audio out.

imageFor anyone who has used one of these types of devices, the two standout features mentioned above should be the audio jack, and the addition of Bluetooth. Why? Because this expands the potential functionality of the device manyfold. Beforehand, the lack of Bluetooth made adding peripherals — such as a mouse of keyboard — either difficult, or impractical. However, with Bluetooth, setting up this device to be somewhat useful just got a lot easier. Likewise, with the dedicated audio out, now you can work with sound when the display you are connecting it to (a monitor for example) doesn’t have speakers. Read on after the break to hear more of our impressions. …

image

According to Amazon, the specs for the CozySwan unit (edited for clarity) are as follows:

  • imageOperating System: Google Android 4.1.1 Jelly Bean with Bluetooth
  • CPU: RK3066 1.6GHZ Dual ARM Cortex-A9 processor
  • GPU: Mali 400MP4 quad-core; supports 1080P video (1920 by 1080 pixels)
  • RAM: 1GB DDR3
  • Internal Memory: 8 GB Nand Flash
  • External Memory: Supports Micro-SD card, up to 32GB
  • Networking: WiFi 802.11b/g/n with internal antenna
  • Ports: 1 USB 2.0 host and 1 Micro USB host (see photo at right), 1 HDMI male, 1 Micro-SD card slot
  • Power: 90-230V, 50/60Hz, 30 W input to wall wart; output: 5V/2A
  • Video Decoding:MPEG 2 and 4.H.264; VC-1; Divx; Xvid; RM8/9/10; VP6
  • Video Formats: MKV, TS, TP, M2TS, RM/RMVB, BD-ISO, AVI, MPG, VOB, DAT, ASF, TRP, FLV
  • Audio Decoding: DTS, AC3, LPCM, FLAC, HE-AAC
  • Images: JPEG, PNG, BMP, GIF

Note: There are many similar first-generation devices, such as the MK802, which use the RK3066 CPU, run Android 4.0 and don’t support v4.1 or Bluetooth. Make sure you purchase a second-generation device.

Using a TV set as a monitor reminds me of the early days of the Commodore 64 and the first Apple PCs. Of course today’s HDTVs deliver the resolution for text and graphics that was missing in NTSC/PAL receivers.

Update 7/6/2013: See my First Look at the UG007 and Other Android 4.1+ MiniPC Devices updated 6/20/2013 for more information about Android MiniPCs.