[MOD] Self Powered USB OTG on the HP Touchpad! (v2 Full Size) 11-30-12

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mpgrimm2

Senior Member
Nov 5, 2011
1,760
1,181
Greenville, SC
First:
Major Credit to SDX's FTEN for being first with his very original idea and micro Usb version of this hardware mod. If it weren't for him, I would not have dared to do this.
See his original thread:
Self Powered USB Host on the HP Touchpad! and at RootzWiki

SDX Version of this thread
Rootzwiki Version of this thread

DISCLAIMER: I'm not a dev, nor do I play one on t.v. Use the information and links at your own risk. Read and understand what you're doing FIRST is the best bet. I take no credit for the original idea, just ran a bit farther out on the branch before it broke.

Afterwards be sure to check out:
[Tips and Tricks] OTG (USB Host Support) - Requires kernel support
and
My 2 Port 2 Amp OTG Charger & Mod post further down.

This is a difficult modification that requires you to completely disassemble Touchpad (correct tools a plus), cut and dremel out excess material from the back cover (risk of permanent damage) and display frame. You also need to have some soldering equipment plus skill with very small circuit boards/traces (if you want more than a full size power port) and loads of patience (this took several hours over 4-6 separate days).
Still interested? Have a look:

Parts:
- USB-A Female Connector from a USB Extension cable (and it's spare wire)
(or optional microUSB breakout as FTEN used in his original version)
- Small, thin, SPDT switch (single pole double throw) from a Dollar Store toy, ie "DollarTree"
- VPack PRT-08290 (5v Regulator) and it's PDF Reference file
- micro USB (M) connector from a cable or OTG Adapter (if you can't get the Enable switch landed you'll need this cut up into a plug with the ID pin shorted)
( or maybe AppleCable's Powered OTG Cable )

Tools:
- Spudger Tool set (or similar for cracking open the TP)
- Variable Speed Dremel with "Rotary File" bit
- Decent Soldering Iron (ie: Weller WES51) with small conical tip, and small electrical solder (LeadFree compatible recommended)
- Hobby knife Set (ie X-Acto with various blades and handles)
- Hot Glue Gun and sticks

Basic Disassembly/Reassembly: iFixit's HP Touchpad Battery Removal Guide
(You should be confident with the above. Be prepared to break a few of the 7 clips; superglue helps).

The Finished Product:
5HPTPFinishedOTG4.jpg
 
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mpgrimm2

Senior Member
Nov 5, 2011
1,760
1,181
Greenville, SC
Part 0 - Parts, Planning, & Schematics:

My Original sketch of the wiring schematic for the mod
0HPTPUSBOTGmod.jpg


The 3.7v to 5vdc Step-Up Regulator board
0HPTPVPackPRT-08290wiring.jpg


My wife's Simon Toy supplied the OTG Enable Switch (she wasn't thrilled)
0SimonKeychainforSw1.jpg

0SimonKeychainforSw2.jpg


Here's another option for the switch from my local "DollarTree" store
0Switchoption1.jpg

0Switchoption2.jpg



Here's the Full Size USB-A Extension Cable before and after modifiying
0USB-AExt1.jpg

0USB-AExt2.jpg

Lesson Learned: Go ahead and strip the Potting Material off the USB-A (F) connector to expose the 4 solder points and remove the wires (or at least the 2 DATA lines). I think you will have better success if you "land" the Data wires and OTG Enable Switch wire to the TP's USB Controller Board first and then connect the leads to the USB-A Connector and Enable Switch since those solder points are more durable.
** Make sure that the cable wiring is "Copper Colored" not silver, etc. The copper wire will solder more easily without damage to the USB Controller Board later on **
 
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mpgrimm2

Senior Member
Nov 5, 2011
1,760
1,181
Greenville, SC
Part 1 Pictures (Regulator/Connector Placement and Wiring)

Soldering the Battery leads to the Regulator input (take time to get the length & routing correct)
1HPTPSimSlot08.jpg


* See Previous note about soldering Data and OTG Switch wire to USB Controller Board First *
1HPTPSimSlot09.jpg


Here the 5vdc to the USB connector is soldered to the Regulator Output & a DC Rtn from the regulator is soldered to the switch's "common".
1HPTPSimSlot10.jpg


1HPTPSimSlot12.jpg


1HPTPSimSlot13.jpg
 

mpgrimm2

Senior Member
Nov 5, 2011
1,760
1,181
Greenville, SC
Part 3 Pictures (USB Controller Board info)

4HPTPUsbBoard0.jpg


4HPTPUsbBoardBreakout.jpg


4HPTPUsbBoardPinTrace.jpg


Part 3 Pictures (USB Controller Board info)

Note: You can skip this step if you just want a full size USB-A power port and don't care about it having working "data" communication and OTG Enable Switch (I screwed up the enable switch solder pad).

Please read the notes in the pictures for this section, they will help avoid my mistakes.

4HPTPUsbBoardSoldered0.jpg


4HPTPUsbBoardSoldered1.jpg


4HPTPUsbBoardSoldered2.jpg


4HPTPUsbBoardSoldered3.jpg
 

mpgrimm2

Senior Member
Nov 5, 2011
1,760
1,181
Greenville, SC
Additional Reference Info

Here'a an OTG Cable reference schematic that I made to help people make their own OTG cables and OTG shorting plugs. It works as a good reference to figure out how a purchased cable is wired up (some are different).
USBOTGCableSchemReference.jpg


And here's a picture of the micro-USB breakout board (4pins only) from Sparkfun.com that Ften used in his original mod mentioned at the top of the OP. If you prefer, you can squeeze this into the sim slot without dremeling the back cover to a "paper thinness" and hook up your data and pwr to it, but you will have to make or purchase a male microUSB to USB-A adapter (an OTG one would work since there isn't an ID pin hooked up). I avoided this option because I don't want someone hooking it up to a USB wall charger by accident and possibly killing the regulator
microUSBBreakout.jpg
 

mpgrimm2

Senior Member
Nov 5, 2011
1,760
1,181
Greenville, SC
2 Port 2Amp USB OTG Charger & Mod

Here's an update...

My CrazyOnDigital 2 port charger doesn't have the data pins shorted (D+ and D-) like the stock HTC unit. This causes any "Android" phone to charge at the lower 500ma Max "Charging USB" rate vs "AC Charging" (explains my slow charging when travelling), but a bonus is that it allows me to pass data b/w the 2 ports like a simple hub.

- If the D+ and D- pins are shorted when an OTG USB cable is plugged in, the phone/device will go into "AC Charging" mode, but not allow OTG devices to work, but if the phone is still connected and the data pins opened back up, you retain "AC Charging" mode and have USB OTG functions.
(I'm thinking that a simple on/off switch installed across the data pins of my charger will give me a dual mode charger).

AC CHARGING / USB CHARGING (Data Pass Through) MOD 12-1-12
- I got tired of having a 2 port 2 Amp charger that only allowed 500ma "USB Charging" with Android & OTG. See pix:

CoDOTGFastChargeMod0.jpg

CoDOTGFastChargeMod1.jpg

CoDOTGFastChargeMod2.jpg

CoDOTGFastChargeMod3.jpg

CoDOTGFastChargeMod5.jpg

CoDOTGFastChargeMod6.jpg

OrigOTGSetup1.jpg
 
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S

-SGA-

Guest
Since breaking my power button and not knowing where to find a replacement part, I am very interested in what you are doing here.

I was considering finding a way to install an SDHC card in the same spot you've done your USB port. Do you imagine that there would be any additional complications?

I'd also like to add a power switch via the battery.

Sent from my SAMSUNG-SGH-T989 using xda premium
 

sstar

Senior Member
Apr 6, 2012
1,344
469
Brighton
Since breaking my power button and not knowing where to find a replacement part, I am very interested in what you are doing here.

I was considering finding a way to install an SDHC card in the same spot you've done your USB port. Do you imagine that there would be any additional complications?

I'd also like to add a power switch via the battery.

Sent from my SAMSUNG-SGH-T989 using xda premium
In case you not aware there is an app called Button Saviour that can mimic all your hardware buttons including power.

Edit which I have just realised is of no help whatsoever if your Tablet is off . Best of luck.
 
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mpgrimm2

Senior Member
Nov 5, 2011
1,760
1,181
Greenville, SC
Since breaking my power button and not knowing where to find a replacement part, I am very interested in what you are doing here.

I was considering finding a way to install an SDHC card in the same spot you've done your USB port. Do you imagine that there would be any additional complications?

I'd also like to add a power switch via the battery.

My suggestion for the power switch would be to get another TP off Ebay to rob for the switch (probably the only way I will get another USB board to finish my OTG mod 100%). I saw the guts of a 16gb (no screen assy) go for $41 the other day.

As for an SDHC card, don't know. You'd probably have to connect it the same way as the OTG connector (pwr & Data). You'd still need the switch or OTG plug to get the TP to check the bus, the 5v step up to pwr it, some sort of micro-Sd "socket (so there's room for the switch) and an app like "StickMount" to mount it for use. Ultimately, it'd still be OTG but without the option to connect anything else. I'd recommend the OTG port instead.

Edit: I updated Part 4 pictures with a fillet around the port and added a link to the OTG Tips & Tricks Thread (Evo3D)
 
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amkaos

Senior Member
Jun 17, 2008
637
17
i saw the orig post you referred to in your OP..
altho i like it very much and admire your work, i will never
be qualified to attempt it..

i just wonder why the cable still has to run outside from your new usb port to the micro usb port.

is it stupid to ask why it could not permanently connect from the inside and use a switch for charging / data transfer ?

again, i will never be able to do this so you could ignore this post..

also, from your evo 3d thread, i see that someone uses a 4 port 12000mah
battery charger for data... is this correct?..

i use a solar powered 4 port hub but would like to see a battery charger modded to charger / data transfer w/ a switch..
the solar hub of mine doesnt last so long

thanx foryour reply..
 
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mpgrimm2

Senior Member
Nov 5, 2011
1,760
1,181
Greenville, SC
i just wonder why the cable still has to run outside from your new usb port to the micro usb port.

is it stupid to ask why it could not permanently connect from the inside and use a switch for charging / data transfer?

Look closer at the USB Board post pictures. If the OTG switch wire is connected to the board internally, then no external setup is needed. I damaged the board just enough that I couldn't finish it until I can locate another board.
Others may not be willing to attempt the board soldering and choose only a full size power port (or microUSB) that needs the external cable that provides power back to the otg device plugged into the original port.


Sent from my "Up all night, Sleep all day" EVO3D!
 
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amkaos

Senior Member
Jun 17, 2008
637
17
Look closer at the USB Board post pictures. If the OTG switch wire is connected to the board internally, then no external setup is needed. I damaged the board just enough that I couldn't finish it until I can locate another board.
Others may not be willing to attempt the board soldering and choose only a full size power port that needs the external cable that provides power back to the otg device plugged into the original port.


Sent from my "Up all night, Sleep all day" EVO3D!

thanx for the explanation.. i get it now..that makes so much sense

do you know what i was speaking of relating to the mod to a battery charger to switch between charge / otg ?

if possible to do , i could attempt that mod
 

mpgrimm2

Senior Member
Nov 5, 2011
1,760
1,181
Greenville, SC
also, from your evo 3d thread, i see that someone uses a 4 port 12000mah
battery charger for data... is this correct?..

i use a solar powered 4 port hub but would like to see a battery charger modded to charger / data transfer w/ a switch..
the solar hub of mine doesnt last so long
I'm not sure what u mean by this. Post some links or quote the post and I will see if I can figure it out.

Sent from my "Up all night, sleep all day" HP CM9 Touchpad
 

amkaos

Senior Member
Jun 17, 2008
637
17
shoot... sorry i thought i did link...

http://forum.xda-developers.com/showthread.php?t=1916638

to me , this is interesting because the OP shows a modded OTG cable to connect the mini port on his solar hub to the micro port of his evo3d..

this eliminates one cable:: from hub mini port to OTG usb..

he does say how it works but i dont know if the mod would be exactly the same for our HPTP..

i have that same self powered hub and it works fine.. just not much run time.. maybe 700mah.. iirc

secondly post #2 in that thread speaks of his 12000mah charger. it seems to me like he modded it to do OTG..

this would be good because of how much run time it would have..

could be great if he put on the charger a switch for charge / data transfer if it would need a switch to use like that..

anyway your current mod is soo ambitious but i saw you modded a wall charger ..

thanx again
 
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mpgrimm2

Senior Member
Nov 5, 2011
1,760
1,181
Greenville, SC
OK I see what he did with the charger. It uses an adapter (host) cable to go from the main hub port to the PC (mini-USB to full size USB-A).

It looks like he spliced the micro-USB OTG cable (pin 4&5 shorted) to a mini-USB cable, and made a custom OTG Host cable. He mentions he disconnected/broke the +5v wire to prevent it charging the phone due to the small battery in it. I wouldn't do that myself, but I'd also ideally want a 3000-4000mah Solar Hub to modify for OTG & keeping the phone/tablet charged.

Have a look at my OTG cable schematics in reference post 9 above, particularly cable 1.

Sent from my "Up all night, sleep all day" HP CM9 Touchpad
 
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amkaos

Senior Member
Jun 17, 2008
637
17
OK I see what he did with the charger. It uses an adapter (host) cable to go from the main hub port to the PC (mini-USB to full size USB-A).

It looks like he spliced the micro-USB OTG cable (pin 4&5 shorted) to a mini-USB cable, and made a custom OTG Host cable. He mentions he disconnected/broke the +5v wire to prevent it charging the phone due to the small battery in it. I wouldn't do that myself, but I'd also ideally want a 3000-4000mah Solar Hub to modify for OTG & keeping the phone/tablet charged.

Have a look at my OTG cable schematics in reference post 9 above, particularly cable 1.

Sent from my "Up all night, sleep all day" HP CM9 Touchpad

hi
so his phone supports data / charging at the same time?
but to mod an OTG cable for hptp and the mini usb port Hub, we just need to replace the usb end?
and leave pins 4 and 5 as they are?

How else would you make it instead..

I looked everywhere for a better self powered hub whether replaceable battery or not and would have liked to find something better.

thanx.. maybe I can try to make one
 
Last edited:

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  • 11
    First:
    Major Credit to SDX's FTEN for being first with his very original idea and micro Usb version of this hardware mod. If it weren't for him, I would not have dared to do this.
    See his original thread:
    Self Powered USB Host on the HP Touchpad! and at RootzWiki

    SDX Version of this thread
    Rootzwiki Version of this thread

    DISCLAIMER: I'm not a dev, nor do I play one on t.v. Use the information and links at your own risk. Read and understand what you're doing FIRST is the best bet. I take no credit for the original idea, just ran a bit farther out on the branch before it broke.

    Afterwards be sure to check out:
    [Tips and Tricks] OTG (USB Host Support) - Requires kernel support
    and
    My 2 Port 2 Amp OTG Charger & Mod post further down.

    This is a difficult modification that requires you to completely disassemble Touchpad (correct tools a plus), cut and dremel out excess material from the back cover (risk of permanent damage) and display frame. You also need to have some soldering equipment plus skill with very small circuit boards/traces (if you want more than a full size power port) and loads of patience (this took several hours over 4-6 separate days).
    Still interested? Have a look:

    Parts:
    - USB-A Female Connector from a USB Extension cable (and it's spare wire)
    (or optional microUSB breakout as FTEN used in his original version)
    - Small, thin, SPDT switch (single pole double throw) from a Dollar Store toy, ie "DollarTree"
    - VPack PRT-08290 (5v Regulator) and it's PDF Reference file
    - micro USB (M) connector from a cable or OTG Adapter (if you can't get the Enable switch landed you'll need this cut up into a plug with the ID pin shorted)
    ( or maybe AppleCable's Powered OTG Cable )

    Tools:
    - Spudger Tool set (or similar for cracking open the TP)
    - Variable Speed Dremel with "Rotary File" bit
    - Decent Soldering Iron (ie: Weller WES51) with small conical tip, and small electrical solder (LeadFree compatible recommended)
    - Hobby knife Set (ie X-Acto with various blades and handles)
    - Hot Glue Gun and sticks

    Basic Disassembly/Reassembly: iFixit's HP Touchpad Battery Removal Guide
    (You should be confident with the above. Be prepared to break a few of the 7 clips; superglue helps).

    The Finished Product:
    5HPTPFinishedOTG4.jpg
    4
    Part 4 Pictures (finished)

    5HPTPFinishedOTG2.jpg


    5HPTPFinishedOTG3.jpg


    5HPTPFinishedOTG1.jpg


    5HPTPFinishedOTG4.jpg


    5HPTPFinishedOTG6.jpg


    5HPTPFinishedOTG7.jpg


    Updated: 12-3-12
    5HPTPFinishedOTG8.jpg
    3
    Part 1 Pictures (MB Power Leads and Routing):

    1HPTPmbpwr1.jpg


    1HPTPmbpwr2.jpg


    1HPTPmbpwrRouting.jpg
    3
    Part 1 pictures (Sim Slot Modification & Test Fitting):

    1HPTPSimSlot01.jpg


    1HPTPSimSlot02.jpg


    1HPTPSimSlot03.jpg


    1HPTPSimSlot04.jpg


    1HPTPSimSlot05.jpg


    1HPTPSimSlot06.jpg


    1HPTPSimSlot07.jpg


    When it's all mounted up (Later) the connector will stick out the back like this:
    5HPTPFinishedOTG0.jpg
    3
    Part 1 Pictures (Regulator/Connector Placement and Wiring)

    Soldering the Battery leads to the Regulator input (take time to get the length & routing correct)
    1HPTPSimSlot08.jpg


    * See Previous note about soldering Data and OTG Switch wire to USB Controller Board First *
    1HPTPSimSlot09.jpg


    Here the 5vdc to the USB connector is soldered to the Regulator Output & a DC Rtn from the regulator is soldered to the switch's "common".
    1HPTPSimSlot10.jpg


    1HPTPSimSlot12.jpg


    1HPTPSimSlot13.jpg