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Nexus 7 2012 WiFi Tablet: Issues with OTG Y Cable and 4 USB Hub using Timur's Kernel ROM

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  • #1 16626296
    malaoko
    Level 8  
    Posts: 80
    Rate: 6
    Hello, I recently bought a Nexus 7 WiFi tablet (2012), I downloaded the Timur's Kernel rom because the tablet is used instead of the radio in the car, I bought an Otg Y cable and a regular Hub with 4 usb inputs, the problem is how the power supply to the otg cable and the hub is connected to the tablet finds a hub, but if it has a device connected to a USB flash drive, USB sound card, USB reversing camera or USB Dac, the tablet does not search for any device.
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  • #2 16627184
    gradek83
    Level 43  
    Posts: 9048
    Help: 925
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    Your USB HUB to a separate power socket?
    This is more or less the schematic of the OTG Y cable
    Nexus 7 2012 WiFi Tablet: Issues with OTG Y Cable and 4 USB Hub using Timur's Kernel ROM

    The outgoing cable is for charging, i.e. you connect it to the USB power socket in the 5V lighter from 0.5A to 2A. The USB hub, if it does not have a separate power supply, receives power from the phone and thus from the cigarette lighter power supply, if connected.

    Take the best picture as you put it together.
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  • #3 16627188
    malaoko
    Level 8  
    Posts: 80
    Rate: 6
    I even disassembled this hub, I unsoldered the cable from the +/- I soldered the power supply from the Dc-Dc converter and left only the cables from the Data + / Data - and then nothing, the tablet shows the 400mb / s hub in the USB device (or I do not remember something exactly) but if I get hooked devices, do not connect them.

    And I have a question, I found such a diagram on the net and if I create it, I will add more usb inputs as in the 2nd photo, will it be ok?
    Attachments:
    • Nexus 7 2012 WiFi Tablet: Issues with OTG Y Cable and 4 USB Hub using Timur's Kernel ROM Y_OTG_CABLE ? kopia.png (41.71 KB) You must be logged in to download this attachment.
    • Nexus 7 2012 WiFi Tablet: Issues with OTG Y Cable and 4 USB Hub using Timur's Kernel ROM Y_OTG_CABLE.png (35.28 KB) You must be logged in to download this attachment.
  • #4 16627191
    gradek83
    Level 43  
    Posts: 9048
    Help: 925
    Rate: 2077
    malaoko wrote:
    but if sub-devices do not connect them.

    And without a HUB, as for OTG directly, each device you hook up can see?

    Do you have an ordinary OTG cable? Did you check on such a cable?

    This USB HUB, what you have is USB3 or USB2.0
  • #5 16627192
    malaoko
    Level 8  
    Posts: 80
    Rate: 6
    gradek83 wrote:
    malaoko wrote:
    but if sub-devices do not connect them.

    And without a HUB, as for OTG directly, each device you hook up can see?

    This is how every device sees, I just care about supporting it:
    -pendrive
    -dac usb
    - reversing camera
    -tuner dvbt
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  • #6 16627196
    gradek83
    Level 43  
    Posts: 9048
    Help: 925
    Rate: 2077
    malaoko wrote:
    This is how every device sees, I just care about supporting it:
    -pendrive
    -dac usb
    - reversing camera
    -tuner dvbt

    Probably the USB HUB is to blame, for example, on an ordinary OTG, I connected the USB HUB and the CAMERA and PENDRIVE to it, and this and it works. Of course, under the samsung galaxy s4.

    Nexus 7 2012 WiFi Tablet: Issues with OTG Y Cable and 4 USB Hub using Timur's Kernel ROM

    malaoko wrote:
    You can upload a link or photo to your hub.

    I have a UH473 on the GL850G chip
    Nexus 7 2012 WiFi Tablet: Issues with OTG Y Cable and 4 USB Hub using Timur's Kernel ROM Nexus 7 2012 WiFi Tablet: Issues with OTG Y Cable and 4 USB Hub using Timur's Kernel ROM
  • #7 16627199
    malaoko
    Level 8  
    Posts: 80
    Rate: 6
    gradek83 wrote:
    malaoko wrote:
    This is how every device sees, I just care about supporting it:
    -pendrive
    -dac usb
    - reversing camera
    -tuner dvbt

    Probably the USB HUB is to blame, for example, on an ordinary OTG, I connected the USB HUB and the CAMERA and PENDRIVE to it, and this and it works. Of course, under the samsung galaxy s4.

    Above I threw a cable diagram, you can look.
    I bought one and it had a processor inside, when I measured it with a cable continuity meter, if I put it on the DATA + input, there was no continuity on DATA + behind the processor on the usb inputs. It seems to me that this processor just goes crazy. You can upload a link or photo to your hub.
    Attachments:
    • Nexus 7 2012 WiFi Tablet: Issues with OTG Y Cable and 4 USB Hub using Timur's Kernel ROM 1364610622.9391.jpg (102.99 KB) You must be logged in to download this attachment.
  • #8 16627209
    gradek83
    Level 43  
    Posts: 9048
    Help: 925
    Rate: 2077
    This cable is quite long for you, maybe the losses are too high.
  • #9 16627212
    malaoko
    Level 8  
    Posts: 80
    Rate: 6
    gradek83 wrote:
    This cable is quite long for you, maybe the losses are too high.

    There may be losses on data transmission?
    because I gave a short power cable to what I soldered to +/-.
  • #10 16627214
    gradek83
    Level 43  
    Posts: 9048
    Help: 925
    Rate: 2077
    malaoko wrote:
    gradek83 wrote:
    This cable is quite long for you, maybe the losses are too high.

    There may be losses on data transmission?
    because I gave a short power cable to what I soldered to +/-.

    Not data, but power loss.
    Check if you connect the HUB to a PC or Laptop, whether it works normally and whether, for example, after connecting a USB cable and, for example, a Phone to it, will it detect the phone and e.g. charging will be OK?
  • #11 16627220
    malaoko
    Level 8  
    Posts: 80
    Rate: 6
    gradek83 wrote:
    malaoko wrote:
    gradek83 wrote:
    This cable is quite long for you, maybe the losses are too high.

    There may be losses on data transmission?
    because I gave a short power cable to what I soldered to +/-.

    Not data, but power loss.
    Check if you connect the HUB to a PC or Laptop, whether it works normally and whether, for example, after connecting a USB cable and, for example, a Phone to it, will it detect the phone and e.g. charging will be OK?

    I also have a problem with signal interference, I created a topic in car audio but it is related to the tablet too, maybe you will look? https://www.elektroda.pl/rtvforum/topic3365864.html
  • #12 16627597
    gradek83
    Level 43  
    Posts: 9048
    Help: 925
    Rate: 2077
    malaoko wrote:
    I also have a problem with signal interference

    From what the sources say, you plug in the AUDIO anti-interference filter between the DAC and AMP

    Nexus 7 2012 WiFi Tablet: Issues with OTG Y Cable and 4 USB Hub using Timur's Kernel ROM

    unless I am mistaken RCA anti-interference filter
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  • #13 16627693
    malaoko
    Level 8  
    Posts: 80
    Rate: 6
    gradek83 wrote:
    malaoko wrote:
    I also have a problem with signal interference

    From what the sources say, you plug in the AUDIO anti-interference filter between the DAC and AMP

    Nexus 7 2012 WiFi Tablet: Issues with OTG Y Cable and 4 USB Hub using Timur's Kernel ROM

    unless I am mistaken RCA anti-interference filter

    i.e. between give and amplifier? because the audio signal to the Dac goes via usb and the jack comes out to the amplifier
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Topic summary

✨ The discussion revolves around issues faced by a user with a Nexus 7 (2012) WiFi tablet when using an OTG Y cable and a 4-port USB hub powered by Timur's Kernel ROM. The user reports that while the tablet recognizes the hub, it fails to detect connected devices such as USB flash drives, sound cards, and cameras. Responses suggest checking the power supply to the hub, as insufficient power may prevent device recognition. Suggestions include using a powered USB hub, testing devices directly with an OTG cable, and ensuring proper wiring and connections. Signal interference issues are also mentioned, with recommendations for using audio anti-interference filters.
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FAQ

TL;DR: For a Nexus 7 (2012) car install, power the OTG Y cable with 5V at 0.5–2A and remember: "The outgoing cable is for charging." [Elektroda, gradek83, post #16627184] Why it matters: This prevents hub under‑powering so USB storage, DACs, and cameras enumerate reliably—vital for in‑car stability.

Quick Facts

Why won’t my Nexus 7 see devices through a powered USB hub?

Power mods or hub electronics can block D+/D− continuity, so devices never enumerate. One user rewired power via DC‑DC, left only data lines, and Android still only saw the hub, not devices. Avoid hubs that alter data paths and test stock before modding. [Elektroda, malaoko, post #16627188]

Do devices work when connected directly with an OTG cable?

Yes. The tablet detected every tested device when plugged in directly via a basic OTG cable. Confirmed devices included a pendrive, a USB DAC, a reversing camera, and a DVB‑T tuner. If your hub fails, validate each device direct‑to‑OTG first to isolate the fault. [Elektroda, malaoko, post #16627192]

How much current should I feed the OTG Y cable in a car?

Supply 5V at approximately 0.5–2A from a cigarette‑lighter USB adapter to the Y‑cable’s charge lead. As one expert put it, "The outgoing cable is for charging." This ensures the hub and tablet have adequate power headroom during device enumeration and steady operation. [Elektroda, gradek83, post #16627184]

Is cable length really my problem?

Likely yes. Long runs drop voltage, starving the hub and peripherals. "Not data, but power loss." Shorten the 5V path or use thicker conductors to keep voltage near 5V under load. This single fix often restores stable detection and charging. [Elektroda, gradek83, post #16627214]

How can I quickly test whether my USB hub is healthy?

Try it on a PC or laptop. Plug the hub into the computer, then connect a phone or storage device. Verify enumeration and, for phones, that charging starts. If it fails on a PC, the hub or wiring is suspect; replace or revert modifications. [Elektroda, gradek83, post #16627214]

Which hub controller has been seen working in practice?

A UH473 hub using the GL850G controller was shown handling a camera and pendrive when paired with a phone. This demonstrates that a straightforward USB 2.0 hub can enumerate multiple devices when powered and wired correctly. [Elektroda, gradek83, post #16627196]

Can I just splice more USB inputs by joining D+ and D− wires?

No. A user attempted custom wiring, powering +/− via DC‑DC and leaving only D+/D−. Android saw the hub but never any attached devices. Use a proper USB hub IC with per‑port switching, not passive splits of data lines. [Elektroda, malaoko, post #16627188]

I see ~400 Mb/s for the hub in Android—what does that mean?

That readout aligns with a USB 2.0 High‑Speed hub being detected. It only indicates the hub link speed, not that connected peripherals are active. If devices still don’t appear, focus on power integrity and hub design. [Elektroda, malaoko, post #16627188]

How do I eliminate alternator whine or ground‑loop noise with a USB DAC?

Insert an audio anti‑interference (RCA ground‑loop isolator) filter between the DAC’s analog output and the amplifier input. This breaks the noise path while preserving signal, restoring clean audio during engine operation. [Elektroda, gradek83, post #16627597]

Exactly where do I place the RCA filter in this setup?

USB carries digital audio into the DAC, then the DAC’s 3.5mm/RCA analog output feeds the amplifier. Place the filter inline between the DAC output and the amp input. This location addresses the analog ground loop. [Elektroda, malaoko, post #16627693]

Should I choose a USB 2.0 or USB 3.0 hub for Nexus 7 (2012)?

Start with a straightforward USB 2.0 hub. The working example used a GL850G‑based unit and handled camera plus storage reliably. USB 2.0 reduces complexity and matches the tablet’s expected host capabilities. [Elektroda, gradek83, post #16627196]

What is an OTG Y cable and why do I need it here?

An OTG Y cable lets the tablet act as USB host while receiving 5V power on a separate leg. In car installs, it keeps the tablet charged and the hub powered, preventing brownouts during device enumeration. [Elektroda, gradek83, post #16627184]

What is Timur’s Kernel ROM in this context?

The OP used a custom kernel/ROM so the Nexus 7 could serve as a car head unit. Their issue centered on OTG Y‑cable and a 4‑port hub not enumerating devices when powered. [Elektroda, malaoko, post #16626296]

Can a phone and storage work together on a small hub?

Yes, as demonstrated with a camera and pendrive on a GL850G‑based hub. That indicates multi‑device enumeration works when the hub and power are correct. Two ports active is typical on compact 4‑port hubs. [Elektroda, gradek83, post #16627196]

Any edge cases after re‑powering a hub from a DC‑DC converter?

Yes. After separating power and leaving only D+/D−, Android detected the hub but never attached devices. This failure suggests the hub’s internal logic or wiring mod broke proper USB negotiation. [Elektroda, malaoko, post #16627188]

How do I troubleshoot Nexus 7 OTG hub issues in three steps?

  1. Test the hub on a PC; confirm device detection and phone charging.
  2. Shorten and thicken the 5V path; avoid long cables.
  3. Re‑try the tablet with direct OTG to validate each device, then reinsert the hub. [Elektroda, gradek83, post #16627214]
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