Audio Out via USB

[Bimmerjo]

Wow Dave, (if I may call you that) nice post!

 

[hazydave]

Well, pretty much all media players that support USB are using it the same way (mount the device as storage media) so I think it makes sense for Droid to support that mode of operation.

Of course. And it does. Lots of players can support playback from USB... the GPS device in my car, for example, can play directly from the DROID, or a USB stick, or SDHC card, or an iPod...

 

[QiG]

After reading this thread, my questions is: My car radio has a USB port (and an ipod hookup through the glovebox), so I was wondering what my options are if I wanted to output through the 3.5mm port. Are there cables that are 3.5mm on one end and USB (A) on the other? Or if I had to, 3.5mm male and ipod female on the other end? Thanks

EDIT: Oops, completely didn't realize that the head unit runs a male 3.5 jack to the glovebox as well so I'm farther ahead in the game than I realized. I think I'm better off running this cord to the area under the dashboard though since it's not very practical to have my glovebox open while driving. I would have expected a female port on the face of the radio if anything. Someone might have a similar question though so I'll leave this up.

 

[flyboy472]

Bump...

Ok so for those of us who don't have bluetooth or fancy car stereos with USB hookups, would there be a way to design a dock that would simultaneously charge the phone and allow an audio hookup through only the micro USB connector?

I'm not familiar with the nitty-gritty of Android. Can apps interact with the USB port? If so, could an app be designed to take sound that would normally be sent to either the headphone jack or the phone speaker and instead send it as data over the micro USB port?

If this can be done, a dock could easily be designed that would convert the data into an anolog sound signal. This dock could have the standard mini stereo connection and a charger connection. This way you could mount the dock in your car, connect it to your stereo and your cigarette outlet. Then all you would have to do is insert the Droid into the dock and instantly connect it to your stereo while simultaneously charging it. This as opposed to the current docks that require you to snap the phone in, then connect your charger (if desired), then connect a mini stereo plug for audio.

 

[hazydave]

Bump...

Ok so for those of us who don't have bluetooth or fancy car stereos with USB hookups, would there be a way to design a dock that would simultaneously charge the phone and allow an audio hookup through only the micro USB connector?

You're really barking up the wrong tree here, trying to do this in the most complicated way possible.

USB isn't simply a fountain of analog audio bits, it's an entire protocol. You need a microcontroller at each end of a USB connection, one "host" (usually a PC or similar device), one "target" (usually your DROID, a USB stick, a printer, etc). So yeah, you could put a cradle with a USB jack that treats your DROID as a USB memory device, and includes its own MP3 player... that's basically what happens if I attach my DROID directly to my GPS device.

This could work, but it's a stupid way to hook a DROID into your car stereo. A much better way, if the prospect of a second cable is just to much to deal with, would be to put a dumb USB jack (eg, just the power) in the cradle, and also a Bluetooth chip with audio support. Then you drop your DROID in the cradle, it speaks Bluetooth to the Bluetooth chip, and that chip outputs an audio signal that can route directly to your stereo in some way.

The reason this is superior is that, while the Bluetooth protocol itself is still run between two small microcontrollers, there are modes that work pretty much as a stream of audio bits. So your DROID is still the MP3 player. This is what happens when my DROID hooks up to my Altec Lansing "SoundBlade" device.

If this can be done, a dock could easily be designed that would convert the data into an anolog sound signal.

Again, not really how USB works. USB is essentially a communications protocol. And while you can run audio over it in various ways, the data's always in packets and must be processed into audio by a computer. And other than using the DROID as a USB drive, you'd need extra software to convert to other protocols.

The closest thing to what you want is what you get when you hook "USB Speakers" to a PC. That would require the DROID run in host mode. Apparently, it can.. but it's not currently set up that way, and it would still need extra USB device drivers to configure it as a USB host and to run the audio protocols, assuming the DROID USB interface is even capable of running the USB audio protocols at speed (probably, but who knows). You would still need a USB chip in the cradle... this doesn't save you anything over using Bluetooth. And the Bluetooth solution works today.

This dock could have the standard mini stereo connection and a charger connection.

Did you notice... there's already a standard mini stereo connector on the DROID. You have to consider the economic potential of this... few people would pay an extra $30-$40 just to go from a two-connector dock to a once connector dock.

The nice thing about Bluetooth is that it's a zero connector dock, unless you need a charge. And it'll save you power... Bluetooth over a short distance runs in mode 3, which is 0dBm power (1mW). A regular headphone amplifier on a DROID or other MP3 player might suck down over 200mW, and anything you can hear well in a room, that's probably a few watts of power or more.

This is a temporary problem, anyway, since many if not most new cars have Bluetooth built-in on the stereo system.

If you have a cassette deck in your car, you can also solve this easily using a Bluetooth cassette adapter... yup, the modern cousin of the 1/8" phono jack cassette adapter. Lookie here:
The Abe BT 80C Bluetooth Stereo Cassette -- Engadget
Bluetooth Cassette Tape Adapter | GeekAlerts

Make sure the one you get supports the A2DP protocol.

 

[Penguissimo]

Real USB doesn't stream analog audio... which seems to be what you're after. The RAZR did a hack, to reuse the USB jack for analog cellular headsets.. but that's of no value for high quality audio, anyway.

The iPhone dock does support an analog audio output, which made some sense back in the early 1990s when that iPod dock was first invented. But this isn't the early 1990s. The DROID does a fine job delivering audio via Bluetooth. And this is far superior.

Ok, first, the iPod... those iPod docks only work with iPods. Buy another kind of player, and you're SOL... they don't work with your dock. They also force the form-factor of the iPod.. they can't make one that's larger or much smaller without killing the dock function.

Now Bluetooth... it's an industry standard. I have a nice Altec Lansing SoundBlade sitting over on my desk, which works just dandy from the DROID. The DROID itself uses far less power hooking to that device than it would to an analog dock (because it's just 1mW Bluetooth). Bluetooth also does the remote control standard, so I can FF/REV via buttons on the Soundblade. And I don't even need to take the DROID out of my pocket. Wired docks are SO 20th Century. And if I get a different phone in a few years, it'll work with all the BT accessories I have today, not need toss it all out if I don't buy a Motorola product.

No, that's a bit fail. I don't want to be locked into a single vendor (like Apple) or even a single PC. There's usually no need to sync a DROID... if you make changes to stuff on the DROID, it just automatically syncs to your web-based things. Ok, it is still new (keep in mind, there was a decade or so of iPod before the iPhone came out). Right now, most of the stuff syncs "to the cloud". But in the long run, there's no reason you couldn't have any and all PCs you want also sync to the cloud, so your local apps would just automagically stay in touch with the DROID (or any other Android device).

As for connections... the DROID hooks up via USB, just as it should. And via an industry standard connector (and one engineered for 10's of thousands of plug/unplug cycles)... why would I want something proprietary. And when it's connected, it's a USB storage device. So it works on any platform that can talk to USB storage devices.. I could even hook it to my Sanyo camcorder and download files. Why would I want the proprietary nonsense you get with the iPod/iPhone?

Wired died a long time ago... Apple's just still reacting, poorly. Even if you want PC sync and all, why do you even need to hook it up. You have Wifi on the DROID. Now, sure, Google is all about the net, so media sync via internet may be too slow, but every other kind of sync (contacts, calendar, etc.) is fundamentally superior, because you never NEED to sync.. it just happens.

Former iPod user, recent Droid convert here...I like (and agree with) your points, but I did want to clear something up—the iPod was released in 2001 (not the early 1990s), with the iPhone following up in 2007. And the first iPods used Firewire to connect; the dock connector that we all know and "love" wasn't introduced until 2003. Let's not give Apple too much credit for inventing the modern media player environment

Of course, maybe by the time these things have been out for a couple decades, Apple will have figured out how to make the dock connector less damage-prone and more interoperable. While the wide availability of Dock connector accessories is a slight perk (although woe be unto you who purchases a protective case!), you never know without quite a bit of research which accessory will work with which iPod, and Apple themselves don't exactly trip in their rush to clear things up.

Heck, just take cables. This cable works for charging and syncing, but this cable will only sync. And this third cable (that came with a car accessory) will also stream audio, unlike the first two? But what about this extension cable I can buy? It'll do "everything except audio recording". But then why won't it charge when I plug it into this fancy speaker dock? Oh, because Apple changed the charging standard without telling anyone so they could save a few cents per unit, in the process obsoleting virtually every charging accessory (from the $5 wall charger through the $700 speaker docks) that had been released up until that point. Your choices of remedy? Either buy a clunky $30 adapter or shut up.

Sorry, I got off on a bit of a tangent there...I'm just still excited by the things the Droid doesn't prevent me from doing anymore

 

[flyboy472]

HazyDave: Thanks for the info...I'm ignorant when it comes to tech specs on USB. Surprisingly my car isn't that old, 2005 model, but it lacks bluetooth and USB. It actually didn't even have an audio input, so 2 years ago I purchased an adapter that plugs into the satellite input on the back and has a mini stereo plug on the other end. So I do currently have a method to connect my Droid to the car stereo. Was just hopeful that technology would allow a convenient single connection for both charging and audio. Unfortunately it looks like bluetooth is the most promising solution.

 

[tehpriest]

Why not just get a head unit with BT? The Droid has stereo out via BT so you can then simply stream with no wires Also miost head units with BT will cut in on the music for road reports etc. Job done :motdroidhoriz:

 

[reign]

Ok... for the record, the ipod does NOT send audio through usb. While the connection to the pc may be usb, the audio signal is sent through different 3 different conductors of that same cable. When the ipod is connected to an aftermarket radio that will actually control the ipod, it is doing so through usb mass storage. However, there actually only 4 conductors used in connecting the ipod to the pc via usb. The actual ipod cable has many other conductors for audio and video.

The micro usb connector used to charge the DROID does have more conductors, but not enough to do audio without actually using the 3.5mm at the top of the phone. It would appear that the best way to get an audio signal to an aftermarket stereo, or any other device for that matter, would be through bluetooth.

A friend of mine has one of the newer Kenwood in-dash nav/tv's and synced his DROID to it. VOILA!!!... not only did he have hands free calling AND get the audio from his DROID through his head unit, but he could actually access some (not all) of his apps from his head unit without ever having to touch his phone. The main app of interest to me was Pandora. And YES... full control over Pandora via the kenwood head unit.

My reasoning for wanting a one cable audio/charging connector is that I no longer want a head unit clogging up my dash board. I was running a pc in car for all multimedia and nav purposes. My mobo died and since then have been using my DROID coupled with an Audiocontrol Three.1. Still trying to fine tune the sound b4 I finish all the fab work. But one of my hang ups have been ease of connection. I may try to wire something through the micro usb, or just eventually give up and go with a blue tooth audio adapter.

Anyway, just thought I would add a little insight as to how these things work because with everyone believing that any of these devices actually send audio signal through usb... it is just hindering the progress of anyone figuring out any solution whatsoever.

 

[takeshi]

It would appear that the best way to get an audio signal to an aftermarket stereo, or any other device for that matter, would be through bluetooth.

As usual, depends on what you mean by "best". If you mean "least cables", then yes. It may not be best for those with factory stereos that don't support A2DP and have no intention of adding A2DP support.

 

[Royalcs]

i mean there is a way you could send audio via usb. you just need a usb soundcard and the drivers. like here for the nexus one: Nexus One USB host driver
and since the droid can act as a host with this special cable/dongle maybe we can use some kernel module to support usb soundcards and even mass storage devices

 

[hazydave]

Ok... for the record, the ipod does NOT send audio through usb.

Just as I told y'all last March.

The iPod connector has many signals on it. Among these (depending on model) are USB, analog audio out, power, remote control, video, and Firewire (on older models). People may think of the iPod connector as "just USB", but it's not.

As well, a very small number of cellphones, such as the Motorola RAZR, multiplexed analog audio I/O on the USB connector. Basically, the phone detected USB, and if it didn't see the USB connection (probably by sensing the USB power), it would switch the headset signals in place of the USB signals.

USB is and always was a digital-only signal. And on most phones, you only have the USB Target interface -- the phone cannot initiate a USB transaction, only respond to one. So you can even have the phone push digital audio out to something else on its own, over USB. Some devices, like my Pioneer GPS, have USB host interfaces that can read data from a phone (or other USB device, such as a memory dongle or hard drive) and play it.. but that's the other device doing most of the work.

For digital playback on another device, with a modern smart phone, Bluetooth is your best bet.

While the connection to the pc may be usb, the audio signal is sent through different 3 different conductors of that same cable. When the ipod is connected to an aftermarket radio that will actually control the ipod, it is doing so through usb mass storage.

Actually, there are more signals there than you think.. the iPod connector has 30 signals, as well as a shield ground around the whole thing. There is a +5V power input, a +3.3V power output (allows the iPod to power small add-ons), and a bunch of ground signals. USB adds the two USB signals, plus a separate ground return for USB. Audio comes out on two pins, but there's only one audio return (ground), which is also shared with video. There are also audio input pins, which are line-level (-12dBV I would assume)... this is how add-in microphone devices get the audio into an iPod. For video, there are actually separate chroma and luma pins, like on an S-Video cable.

Remote units don't use USB just to control the iPod.. there's a 2-way UART, running at 19,200 baud.. more or less like the LANC connector on some camcorders... simple microcontrollers can talk to the iPod this way and give it commands, without the need to be a USB host, which is far more complex.

There's also an add-on sensing input... adding a resistor on this pin (pin 21, in fact), tells the iPod something about the device that's been attached.... different values indicate different devices.

The micro usb connector used to charge the DROID does have more conductors, but not enough to do audio without actually using the 3.5mm at the top of the phone.

The MicroB connector used on the Droid is essentially a thinner, rugged version of the Mini-B connector, which has 5 pins. These are used for power, ground, and the two USB clock/data pins. The fifth is technically to enable USB "on-the-go" devices, though this isn't supported on the Droid, despite the fact that it actually can support "on-the-go".

When USB was invented, there was a strict split between Target devices (keyboard, mouse, memory dongle, hard drive) and Host devices (your PC). This is different than, say, Firewire, in which every device is technically a peer... host USB devices are much more complex than target devices.

What they didn't consider was a device, like a PDA or Smartphone, that might want to do both... I might want it to be a target when connected to a PC, or a host when connected to some other device.... I have a camcorder, for example, that hooks to my PC like a storage device, but when hooked to a USB storage device, can do its own offloading of data to that device. This 5th pin is used for that.

The Mini-B connector enabled this, and was fine for the early days. But more recently, they've changed the specs. Today, an on-the-go device is only supposed to have the Micro-AB connector... that's the one that's about as thin as the Micro-B, but not as wide, and more square. When you have an on-the-go device (OTG), the cable you plug in tells the device, via this extra pin, that it's supposed to be a host... if it can be. That's why they change the connector spec... all devices with Micro-AB connectors are supposed to be on-the-go.

Of course, no cellphone will use this connector, even if it does add on-the-go, since the Micro-B is not the standard for phones, and it's also far more rugged than other USB connectors.

It would appear that the best way to get an audio signal to an aftermarket stereo, or any other device for that matter, would be through bluetooth.

Just as I wrote here back in March.

A friend of mine has one of the newer Kenwood in-dash nav/tv's and synced his DROID to it. VOILA!!!... not only did he have hands free calling AND get the audio from his DROID through his head unit, but he could actually access some (not all) of his apps from his head unit without ever having to touch his phone. The main app of interest to me was Pandora. And YES... full control over Pandora via the kenwood head unit.

Yup. Bluetooth is the right answer here, mainly because there are a whole bunch of standard protocols supported by it. USB devices may perform a few tricks... your USB device could present itself as storage, or maybe a sound card, but that's about all... and it would be hard pressed to do both.

Bluetooth has a large number of protocols. Not every device supports every protocol, but most GPS/Handsfree device and smartphones have some area of agreement. There's the "Handsfree" protocol, which actually combines the "remote control" and "Headset" protocols... you can push buttons on a foreign device that get sent, in standard ways, to your phone, and you can talk to it and hear back from it. There's also a hi-fi audio protocol... my GPS doesn't have this, but my Altec Lansing "Sound Blade" does, and sounds just dandy playing music back from the Droid. There's also the "Object Exchance" protocol, which lets data move back and forth -- so my phone sent my whole address book to my GPS using this. There's also a plain serial protocol, which replaces RS-232... my old PDA used this to talk to GPS dongles, for example. There's also a cordless phone protocol... most cellphone makers don't implement this, but if they did, you could hook into your home cordless phone system over Bluetooth and make calls from your cell over your landline. Curiously, I have a cordless phone that works the opposite way... I can make and answer calls from/to my Droid via that cordless phone.

My reasoning for wanting a one cable audio/charging connector is that I no longer want a head unit clogging up my dash board. I was running a pc in car for all multimedia and nav purposes. My mobo died and since then have been using my DROID coupled with an Audiocontrol Three.1. Still trying to fine tune the sound b4 I finish all the fab work. But one of my hang ups have been ease of connection. I may try to wire something through the micro usb, or just eventually give up and go with a blue tooth audio adapter.

You ought to use Bluetooth for the audio connection, and fix one of those Droid desktop cradles (or something like it) in the car to hold and power the Droid. Then you're virtually "zero" cable. And if a PC's in charge, Bluetooth is a done-deal, assuming you have a free USB port and $15 or so for the USB dongle. Linux and Windows support most Bluetooth protocols.

 

[JimmyD]

Awesome post Hazydave! dancedroid

.....The MicroB connector used on the Droid is essentially a thinner, rugged version of the Mini-B connector, which has 5 pins. These are used for power, ground, and the two USB clock/data pins.....

I do have a question specifically related to the pin configurations of typical Droid USB cable (male TypeA to male Micro-B).

Could you please tell me what number pin (as labeled in the pic below) corresponds to the function of power / ground / data / data / on-the-go for the Micro-B example?

Also, could you please do the same for the Type A example? (...and with Type A, is it simply power / ground / data / data without on-the-go capabilities, since there's only 4 pins versus 5?)

THANKS!

 

[Stachre]

Sorry for resurrecting an old thread, but I came across both this question and an answer to it during research tonight.

I do have a question specifically related to the pin configurations of typical Droid USB cable (male TypeA to male Micro-B).

Could you please tell me what number pin (as labeled in the pic below) corresponds to the function of power / ground / data / data / on-the-go for the Micro-B example?

The following article details hacking an iPod dock connector for use with the Droid (audio still routed out the headphone jack, unfortunately), and it includes a diagram of the Droid's micro USB pinouts (device side; invert for cable):

iPod dock adapter for Motorola Droid/Milestone

Scroll down to (or find) "Micro USB pinout". According to the diagram, the pinouts would match up to the numbered pins in your Micro-B (cable) connector illustration as follows:

1. Vcc
2. Data-
3. Data+
4. (not marked)
5. GND

At first, I was going to assume that the unmarked pin was the ID (OTG); however, I came across some info on the Nexus One indicating its being connected to the ground, so it's a bit nebulous at this point.