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Can you charge & USB Host mode simultaneously?

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jmcguire525

jmcguire525

Android Lover

  • 102 posts

Posted 16 November 2012 - 06:56 PM #111

Timur, from what I have found the DAC will NEVER connect unless it is booted up with everything connected, and for me and the other people wanting this to work for car audio I don't think that is really a problem. The real issue is once you boot up with the DAC connected you should be able to disconnect the DAC and reconnect easily, I say you should b/c once you disconnect the DAC the audio is never routed back to the internal speakers. The N7 still is being told to use USB audio, it seems to just have a handshaking problem with the DAC. I wish I had a dozen different DAC's to try out b/c there may be a few that don't cause this problem.
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Timur

Timur

Android Master

Posted 16 November 2012 - 09:36 PM #112

Can I ask what you have found out?
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RWNube

RWNube

Android Beginner

  • 81 posts

Posted 16 November 2012 - 09:50 PM #113

If I unplug my Fiio E 17 with Patch 2 (haven't tried Patch 3 yet), I can plug it back in and it plays totally fine as long as I start the song over or play something else.
Same exact thing if I unplug the USB charger from the OTG Y cable and plug the charger back in.

Sent from my ADR6425LVW using Tapatalk 2
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jmcguire525

jmcguire525

Android Lover

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Posted 17 November 2012 - 12:13 AM #114

If I unplug my Fiio E 17 with Patch 2 (haven't tried Patch 3 yet), I can plug it back in and it plays totally fine as long as I start the song over or play something else.
Same exact thing if I unplug the USB charger from the OTG Y cable and plug the charger back in.

Sent from my ADR6425LVW using Tapatalk 2


I've had the same experience five times in a row before, but then tried it the next day and it didn't work.
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nexus-fan

nexus-fan

Android

  • 141 posts

Posted 17 November 2012 - 12:41 AM #115

Hi all,
Sorry for my english.

First timur, thank you so much for your efforts.

The problem i found is that when i disconnect the charge cable i must reboot the
nexus, in all other case i can plug\unplug the dac but
in this situation we have a big problem (for Car) because its
not a problem to charge the nexus all the time but
to "stay awake" all the time i dont think so "healthy".

the current solution is to download toggle widget that change stay-awake mode on\off,

btw, i plan to purchase the nexus 4G in the future so the question is if the
CM10 for regular nexus and patches should working on the new device???
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puffmais

puffmais

Member

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Posted 17 November 2012 - 12:53 AM #116

with patch 3 installed i found out yesterday, that i can power down the usb hub with dac is connected and a song is still playing in the background, that when i repower the hub when nexus 7 lockscreen is on, and than pause the song and after few seconds i can play the song and the sound comes trough usb dac!

but if i power down the hub, song is stopped playing and lockscreen get on, than after repowering no sound comes through usb dac until i reboot or disconnect otg cable.
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jmcguire525

jmcguire525

Android Lover

  • 102 posts

Posted 17 November 2012 - 01:10 AM #117

I think I have a solution that will work on the hardware side. The picture should be self explanatory, V&G are your power and ground +&- are your data wires. This should allow the DAC to stay on at all times by being connected to the hot wire in the car and the tablet will be connected so that it only has power when the car is running.

Posted Image
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kevincat3556

kevincat3556

Android Lover

  • 177 posts

Posted 17 November 2012 - 02:00 PM #118

I think I have a solution that will work on the hardware side. The picture should be self explanatory, V&G are your power and ground +&- are your data wires. This should allow the DAC to stay on at all times by being connected to the hot wire in the car and the tablet will be connected so that it only has power when the car is running.

Posted Image


As long as there is a shared ground somewhere, that should work.
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jmcguire525

jmcguire525

Android Lover

  • 102 posts

Posted 17 November 2012 - 06:32 PM #119

I tested it but didn't have any luck, maybe the DAC needs to get power and data at the same time to turn on. When you say there should be a shared ground can you elaborate?
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Timur

Timur

Android Master

Posted 18 November 2012 - 02:31 PM #120

I now better understand what is going on with the USB DAC and the N7. It's actually trivial. My findings:

* usbaudio is NOT enabled by default in JB/CM10, but can be enabled easily.
* usbaudio can be enabled as a static kernel component only. It does not seem to work when enabled as a loadable module. (Probably due to the fact that everything else is also statically bound.)
* usbaudio only checks for a USB DAC being connected during boot. Switching between USB DAC and internal sound card always requires a system reboot. (A N7 with faster flash, booting in under 15 seconds, might be an advantage :-)
* Once a USB DAC device is detected during boot, it's USB cable can be pulled and plugged any number of times, it will always be rediscovered. This is, until the Android device was restarted without the DAC being connected.
* The behavior of usbaudio is NOT in any way changed or degraded by my patches for powered host mode and charging.
* The behavior of usbaudio is NOT in any way changed or degraded by the Android device being awake, in lock screen or in sleep mode.

I would argue, that "allowing the DAC to stay on at all times by being connected to the hot wire in the car" as described further up, will not provide any real benefits. Once you have connected the DAC to your Android device, you can keep the DAC running or shut it down - as you like - it will always play back audio again when turned on, for as long as the Android device has not been restarted in between. So, for example, over night, I would suggest to disconnect both devices from power. I assume the N7 will stay on in sleep mode for many days or weeks and your DAC experience will be available the next time, as soon as you start the ignition.

The N7 is a little too large for my car. Might give my old Nexus S a try for this purpose...

Edit: typos

Edit2: If you want a patched N7 kernel based on CM10 final but without the full system image (see: msg #98), you can find it here: https://github.com/m...-2012-11-15.img

Edited by Timur, 18 November 2012 - 02:58 PM.

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