USB OTG without external power supply

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lipalok

lipalok

Senior Member
Jul 17, 2013
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Nitra
Hello! Most devices like Nexus 4 or our S4 Mini have problems with USB OTG functionality - they can't provide power to connected device. When I was browsing through some system folders, I've found a directory /d/regulator/8921_usb_otg/8921_usb_otg. In this directory, I can see voltage values, but I'm not able to edit them. Can someone help me how to edit max_uV and min_uV files? Folder called "enable" can be changed to 1, but other folders no.
 

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96DANGER96

96DANGER96

Senior Member
Jul 2, 2011
645
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lipalok said:
Hello! Most devices like Nexus 4 or our S4 Mini have problems with USB OTG functionality - they can't provide power to connected device. When I was browsing through some system folders, I found a directory /d/regulator/8921_usb_otg/8921_usb_otg. In this directory, I can see voltage values, but I'm not able to edit them. Can someone help me how to edit max_uV and min_uV files? Folder called "enable" can be changed to 1, but other folders no.
Click to expand...
Click to collapse

Use ES file explorer, tap the world icon on the top left, Tools, Root Explorer OFF To on, give root permissions, after tap on root explorer again (On the Word now, not on the "ON" button and tap Mount System R/W On the menu that will appear.

Sorry for my english
 
gladson1976

gladson1976

Senior Member
Feb 15, 2008
508
165
Chennai
96DANGER96 said:
Use ES file explorer, tap the world icon on the top left, Tools, Root Explorer OFF To on, give root permissions, after tap on root explorer again (On the Word now, not on the "ON" button and tap Mount System R/W On the menu that will appear.

Sorry for my english
Click to expand...
Click to collapse

From the screenshots he has posted, the folder is already in R/W mode
@lipalok

All the files in that folder have readonly atttibutes set r--r--r--. Try copying the files to some folder in the sdcard, change them, then move them back to the folder and set the same permissions as before.
 
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nuhcan

Senior Member
Jan 26, 2010
50
5
istanbul
lipalok said:
Hello! Most devices like Nexus 4 or our S4 Mini have problems with USB OTG functionality - they can't provide power to connected device. When I was browsing through some system folders, I found a directory /d/regulator/8921_usb_otg/8921_usb_otg. In this directory, I can see voltage values, but I'm not able to edit them. Can someone help me how to edit max_uV and min_uV files? Folder called "enable" can be changed to 1, but other folders no.
Click to expand...
Click to collapse

I'll check my GS2 that has these values and write here...
 
lipalok

lipalok

Senior Member
Jul 17, 2013
88
13
Nitra
gladson1976 said:
From the screenshots he has posted, the folder is already in R/W mode
@lipalok

All the files in that folder have readonly atttibutes set r--r--r--. Try copying the files to some folder in the sdcard, change them, then move them back to the folder and set the same permissions as before.
Click to expand...
Click to collapse

It didn't work :( I'm not able to copy them. Try it on your phone, please.
 
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96DANGER96

96DANGER96

Senior Member
Jul 2, 2011
645
157

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M

marcin1147

Senior Member
Dec 29, 2011
378
2,100
Hi guys!
The "file" you are trying to edit is not a file, but sysfs node.

To set or read a value you do this:
adb shell
su
cd /d/regulator/8921_usb_otg
echo 1 > enable
etc...

try to set max_uV to USB voltage which is 5V, it's in uV so:
echo 5000000 > max_uV
 
lipalok

lipalok

Senior Member
Jul 17, 2013
88
13
Nitra
marcin1147 said:
Hi guys!
The "file" you are trying to edit is not a file, but sysfs node.

To set or read a value you do this:
adb shell
su
cd /d/regulator/8921_usb_otg
echo 1 > enable
etc...

try to set max_uV to USB voltage which is 5V, it's in uV so:
echo 5000000 > max_uV
Click to expand...
Click to collapse

Will try!
@marcin1147
UPDATE: Error, please have a look on screenshot.
 
Last edited:
M

marcin1147

Senior Member
Dec 29, 2011
378
2,100
enable is under /d/regulator/8921_usb_otg not /d/regulator/8921_usb_otg/8921_usb_otg :)
btw. better do this with USB detached, you don't want to fry your PC, don't you? ;)
 
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  • 2
    lipalok
    lipalok
    About USB port

    Right now, I've found an info about USB port that our phone uses.
    It uses TSU6721 USB port, which is made by Texas Instruments® and which officially SUPPORTS OTG.
    Here are some words from their website:
    TSU6721 is a high performance USB port multimedia switch featuring automatic switching and accessory detection. The device connects a common USB port to pass audio, USB data, charging, On The Go (OTG) and factory mode signals. The audio path has negative signal capability includes left (mono/stereo), right (stereo) as well as microphone signals. Furthermore, TSU6721 is compatible with the MCPC specification.
    Anything else you want to know is on their website. Simply google for TSU6721.
    So, we only need a right kernel hack which will enable USB-OTG. Developer @marcin1147 has said that it's possible if some developer will force the kernel to send a voltage from battery to USB port:silly:
    View
    1
    lipalok
    lipalok
    Hello! Most devices like Nexus 4 or our S4 Mini have problems with USB OTG functionality - they can't provide power to connected device. When I was browsing through some system folders, I've found a directory /d/regulator/8921_usb_otg/8921_usb_otg. In this directory, I can see voltage values, but I'm not able to edit them. Can someone help me how to edit max_uV and min_uV files? Folder called "enable" can be changed to 1, but other folders no.
    View
    1
    b0g
    b0g
    no
    View
    1
    junkyde
    junkyde
    I did a little research, but could not find anyone who successfully patched a kernel of a device to provide power through usb port for otg support.

    I only found examples where people managed to integrate usb-otg with external power source.

    So I don't know if it's even possible, because if it was, a skilled developer would have done so...
    View
    1
    lipalok
    lipalok
    junkyde said:
    I did a little research, but could not find anyone who successfully patched a kernel of a device to provide power through usb port for otg support.

    I only found examples where people managed to integrate usb-otg with external power source.


    So I don't know if it's even possible, because if it was, a skilled developer would have done so...
    Click to expand...
    Click to collapse

    @F4k already knows about it, I've written him a message, hope he will be able to do something.
    @junkyde, please have a look here:
    http://xdaforums.com/showthread.php?t=2691624

    It's from S3 Mini thread, which I've personally owned.
    View

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