Making Connections

Mobile DiiVA uses Micro-USB Connector

Posted by Terry Moore
Terry Moore
 
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on Thursday, 08 December 2011 in DiiVA

This is not really USB, but it's using a USB connector. From Interconnection World:

Low pin-count mobile interface extension added to DiiVA specification for unified AV, data, charging power connectivity

According to the article:

The micro-DiiVA receptacle is compatible with micro-USB plugs so devices employing DiiVA can be multi-purposed for both USB and DiiVA functionality.

This raises a number of interesting possibilities, and also a number of interesting questions.

So what's DiiVA? It's the name of a consortium (the "Digital Interactive Interface for Video & Audio" consortium); and it's also the name of their spec for interchanging video, audio, and data for consumer electronics. The home page is www.diiva.org; the member companies include Changhong, Haier, Hisense, Konka, LG, Panda, Samsung, Skyworth, Sony, SVA, TCL and Synerchip.

The spec as described sounds interesting, basically similar to HDMI. The DiiVA FAQ says, "Think of DiiVA as HDMI, USB and Ethernet in one, single low-cost cable." According to the consortium's overview of the spec, it supports uncompressed video (up to 13.5 Gbps), and a multi-purpose Hybrid Channel that carries audio, commands, and bulk data in sub-channels (up to 4 Gbps).

Protocols such as USB and Ethernet can be sent through the bulk data sub-channel, enabling true data sharing between devices.

This is immediately interesting to me, because MCCI has a USB software stack that works on Windows and embedded systems, and doesn't depend on the EHCI or XHCI architecture. Apparently chapter 11 of their specification details how to do USB over their "USB Application Layer".

I was a little puzzled at first as to how the cabling might work, but careful reading of the specification suggests the following interpretation:

  • The mobile DiiVA cable has more pins than a standard USB 2.0 cable (2 twisted pairs plus power, compared to 1 twisted pair plus power for USB 2.0).
  • The mobile DiiVA receptacle looks similar to the super-speed micro A receptacle -- additional pins for the DiiVA-specific functions side-by-side with the pins needed for standard USB 2.0 data transport.
  • Of course, a mobile DiiVA cable will plug into a mobile DiiVA receptacle.
  • A standard micro-USB cable will plug into a mobile DiiVA receptacle, and operate in USB mode. The "extra" pins will not be connected.
  • A mobile DiiVA cable won't physically fit into a USB 2.0 A receptacle, because it's wider (or higher or physically incompatible in some other way).

I can even imagine that they might "mirror image" the USB 3.0 arrangement, so that the super-speed extra pins are on the left-hand side of the connector (as it were), while the DiiVA extra pins are on the right-hand side. With clever circuitry, the DiiVA PHY controller could adjust signalling based on the kind of connector that's plugged in.

On the other hand, there are a lot of interesting problems that arise when running USB over another technology. In particular:

  • Customer confusion: USB connectors are widely deployed. USB 3.0 AV class and DisplayLink USB-to-video adapters will use the same connectors that DiiVA is using. But it's not clear that they'll interoperate. This won't be a great thing.
  • Engineer consfusion: not as important, but it's still an issue. Already we have MirrorLink (which moves audio and video over standard USB, using NCM to simulate Ethernet), AV class (which moves audio and video over standard USB, using a class of its own), and potentially MBIM (which moves audio and video from the cloud using IP protocols over USB). TVs further support storing and playing video using USB thumb drives and USB hard disks with USB Mass Storage Class. Some products use PTP or MTP to transport video. All of these ostensibly use USB. Doubtless Google has some new spec in the wings for use with Android. It's getting hard to keep all these specs straight.
  • USB bus scheduling and timing: USB periodic traffic is scheduled using concepts that are very closely tied to the speed of the bus: 480 Mbps for high speed USB 2.0, 5 Gbps for superspeed USB 3.0. These speeds are "hard wired" into the designs of common products like USB headsets and USB speakers. The speeds of DiiVA's physical layers are different than the speed of traditional USB. I know from experience with Wireless USB and other "almost USB" technoogies that seemingly simple changes in this area can render existing drivers useless. (Demos, by the way, are easy, and prove nothing. The question is whether things will work well in the field.)
  • Cable confusion: The micro USB connector is, well, small. It's not easy to connect cables by feel, and it's really quite hard to tell whether you have the connector oriented correctly. Another connector that's almost, but not completely, the same will be hard to use and will result in connector failures in the field, because customers will try to force things to fit. I always dread hooking things up to my stereo or TV simply because it's so hard to get to the connectors. Not only that, it's dark and dusty at the back of a typical consumer electronic audio-video setup.
  • Utility: where is the micro-DiiVA connector going to be used? Presumably on cell phones and Galaxy Tablets and the like. But if superspeed USB is needed for interop with PCs, and micro-DiiVA is needed for interop with TVs, and these are different connectors, it seems unlikely that there will be room for both superspeed USB and micro-DiiVA. And superspeed USB is going to be ubiquitous. It will be in all next generation application processors for mobile applications. It's not clear to me that a device maker who needs superspeed USB would be able to afford the space or cost for micro-DiiVA support. And if there are no devices, it's not clear that micro-DiiVA will get enough volume production to be successful.

That said, there are a lot of famous companies involved. In addition to the core companies mentioned earlier, contributors include Panasonic, Sharp, Toshiba, Foxconn, Hosiden, JAE, Nikon, Tektronix. Further, there's strong Chinese interest. According to DiiVA's website:

"The DiiVA Mobile Extensions will be an important addition to the Chinese CE ecosystem," said Secretary General of the China Video Industry Association (CVIA), Ms. Weimin Bai. "By using DiiVA technology Chinese manufacturers will be poised to play a large role in the global trend towards convergence of mobile devices with the home entertainment network."

LG, Samsung, and TCL have already certified multiple TVs with the standard DiiVA (not the micro-DiiVA) interface.

One wonders who will have the first DiiVA to USB converter (or vice versa). With superspeed USB, AV class (for audio/video), and NCM (for Ethernet transport), you would have a very interesting connection from PCs to a DiiVA CE cluster.

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Tags: DiiVA, USB

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