Can Tablet PC (android) drive an USB DAC?

[Aiace]

As the subject....
I've made my own DAC and now I need tu use computer to feed it. Looking around I've found out these very cheap Table PCs with ANDROID on board. The question is: have anybody used one of them to drive a DAC based on the Texas (Burr Brown) PCM270x ?


Bye Aiace

[Mikael Abdellah]

not at the moment from what i can gather
Using Android to Drive a USB DAC - Droid Forum - Verizon Droid & the Motorola Droid Forum

[KlipschKid]

Hi,

It's been a few months since the OP asked....and now I wonder what has changed as Android has grown ?

I'm interested to know what the latency of Android is ? How does it compare with Linux, MS and iOS (but no usb on iPad) ? Anyone run any checks ? I typically get around 200u secs using dplact.exe on Win XP.

I'm thinking of getting a slate and plugging in a Teradak Teralink X2 for usb to i2s. Would Android work better than Win7 starter ?

There are quite a few tablets out there due to be released with Android 3.0 Honeycomb and they have usb 2.0 sockets. Here's a link to some of the major players :

Tablets of 2011: What to Look For - TechSpot

Any advice would be greatly appreciated as I know nothing about Android ! I'm sure there are some diyers who are Android fans....

Thanks in advance !

[KlipschKid]

Hi,

All I've managed to find out is that it is possible to hack Android OS with Linux code to host a DAC, but it would not, in theory, be any better than simply using a decent Linux build on decent hardware.

So now I'm more interested in the possibility of hacking something like Asus Express Gate (Linux Splashtop) to support a USB DAC and a good software player.

The research continues....

[KlipschKid]

Here's an Android platform to work from - the Asus Eee Pad Transformer TF-101 - and they just made the Linux kernel available for download even before the thing hits stores.

ASUSTeK Computer Inc. - Eee - ASUS Eee Pad Transformer TF101

Should be quite easy to add in code to support a usb device like Ti PCM270X ?
I say quite easy but then I have no clue how to do this, so I guess I'll have to teach myself.

A page with some help :

http://www.mjmwired.net/kernel/Docum...figuration.txt

[phofman]

Originally Posted by KlipschKid

Should be quite easy to add in code to support a usb device like Ti PCM270X ?

Well, it does not look so easy to me The android kernel differs quite a lot from the mainstream linux. If it was we would be seeing patches around on the web.

[KlipschKid]

Hi,

AFAIK Android 3.0 Honeycomb hasn't been released by Google yet - Asus have done it before them. So I think Asus have posted it on the product page of the TF-101 to encourage the Linux community to get coding.

I'm hoping the Eee Pad Transformer's hardware is good enough to allow very low latencies - something I wouldn't have thought likely in a smartphone - which is why this release might get more interest.

So when I say easy, I mean for people with a very good knowledge of Linux. For me, it's gonna be a long road but I'm up for trying.

[phofman]

Originally Posted by KlipschKid

Hi,

AFAIK Android 3.0 Honeycomb hasn't been released by Google yet - Asus have done it before them. So I think Asus have posted it on the product page of the TF-101 to encourage the Linux community to get coding.

I'm hoping the Eee Pad Transformer's hardware is good enough to allow very low latencies - something I wouldn't have thought likely in a smartphone - which is why this release might get more interest.

So when I say easy, I mean for people with a very good knowledge of Linux. For me, it's gonna be a long road but I'm up for trying.

It is only the android kernel. No android libraries that make up android 3.0 are available.

I am afraid android and linux distributions are quite different beasts, AFAIK they have only the modified linux kernel in common. Did you mean to run recording sessions that you are striving for low latency? It would be a very nice mobile DAW indeed. But I am afraid there are no appropriate recording applications available yet.

[KlipschKid]

Hi,

Hmmm....I must admit my ignorance. I know they haven't let all their cats out of the bag by releasing the whole OS, but I read that Android uses a Linux kernel plus a Dalvik virtual machine to run Java-based apps, so I thought that Asus must have released the Linux kernel part of the OS so that ppl could start creating apps etc for it ? I downloaded it but I have no idea what to look for being a Linux noob.

The hardware is so tasty that I reckon I'm not the only one who'll want this and it'll only be a matter of time before $5 gets me a download that'll allow a usb dac chip like a PCM2707 to export an I2S from it. Even better if I could then hack this to drive a Tenor 7022L chip for 96/24 I2S output. Someone has already hacked the Xoom....

From my experience with Windows, low latency, esp low DPC latency, is what makes USB audio worthwhile.

My desktop has a low DPC latency of around 20us and that is lower than one sample for a PCM 2707 afaik, so I dunno if Android will actually be any better. But I'm always looking to try anything that might be...

Besides anything else, that Eee Pad + external HDD will keep me entertained with movies/music on long haul flights. It'd be great if it could also drive the PCM2707 in the Gamma2 dac so I could enjoy this and my HD650 on flights too.

[phofman]

Originally Posted by KlipschKid

so I thought that Asus must have released the Linux kernel part of the OS so that ppl could start creating apps etc for it ?

Android apps are written on the top of the Dalvik VM. The kernel you have downloaded is below the VM. It is certainly good to have the drivers source code available. Asus had to release the drivers source code anyway, since the kernel is licensed under GPL and Asus is distributing the product with their home-made GPL'd drivers. On the other hand, the dalvik apache license does not have this requirement. AFAIK google has not released the user space android 3.0 source code yet and I would expect it is not available to Asus either.

Originally Posted by KlipschKid

I downloaded it but I have no idea what to look for being a Linux noob.

Even a seasoned linux developer would fight hard with adding alsa usb audio support to android kernel.

Originally Posted by KlipschKid

The hardware is so tasty that I reckon I'm not the only one who'll want this and it'll only be a matter of time before $5 gets me a download that'll allow a usb dac chip like a PCM2707 to export an I2S from it. Even better if I could then hack this to drive a Tenor 7022L chip for 96/24 I2S output.

I think eventually someone (or google itself) will port the existing usb audio 1.0/2.0 drivers. I think android uses the small embedded alsalib (salsa) and the userspace (i.e. the dalvik VM) should not require any major changes.

Originally Posted by KlipschKid

From my experience with Windows, low latency, esp low DPC latency, is what makes USB audio worthwhile.

My desktop has a low DPC latency of around 20us and that is lower than one sample for a PCM 2707 afaik, so I dunno if Android will actually be any better. But I'm always looking to try anything that might be...

See my tests of usb resilience in linux Linux Audio the way to go!? . I do not think you need low system latency for reliable usb playback on properly coded and easily configurable system. You cannot do any of the changes I did with winxp, perhaps that is the reason you are having usb audio dropouts on unoptimized windows PCs.