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Touchpad's USB Cable

31K views 41 replies 23 participants last post by  RolandDeschain79 
#1 ·
My micro usb cable is no longer working (but my charger does), so im wondering if i should look for a specific usb to micro usb cable or anything.

Im asking cause the charger provides 2000 mA while the USB specification is around 900 mA.
 
#7 · (Edited by Moderator)
You're mostly incorrect. Yes, any usb to micro USB cable will "work". However, for it to charge correctly (charge faster than it loses charge), you need a USB Micro B cable (or "Micro-B"). Trust me, I ordered some Micro-A cables and they wouldn't fully charge with the TP turned on. Swapped them out for Micro-B's and now it works just like the OEM cable.

Refer to this post.. http://rootzwiki.com...firmed-working/

and from Wikipedia.. "USB cable, 5 ft (150 cm), with a Standard-A plug and Micro-B plug on its two ends."
 
#8 ·
I'm sorry to say you are talking complete nonsense. Micro USB A male connectors will not fit into a Micro USB B female socket so your claim that they, "wouldn't fully charge with the TP turned on" simply cannot happen.

Obviously when I say "any" cable I do mean the one with the right connector!
 
#10 · (Edited by Moderator)
OK, so I made a mistake.. the cables I bought weren't Micro-A (they had the right connector) but they absolutely would not fully charge the TP. This wasn't just a faulty cable because I bought 5 of them (different lengths) and none would fully charge. I could only get the TP to charge correctly by buying cables that were specifically called Micro-B. I got them from Monoprice BTW and it looks they've merged their product listings since I made that purchase. They actually let me keep the ones that didn't work on the TP and they work perfectly for my phone.
 
#18 · (Edited by Moderator)
It depends how it's wired. The way iDevices detect a mains charger is slightly different to the Touchpad. See the circuit diagram below.

With a standard cable you will get:
51k/(51k+75k) * 5v = 2.02v on Data +
51k/(51k+43k) * 5v = 2.71v on Data -

From the HP implementation above you can see that the TP is expecting the same value on both Data + and Data - namely:
300k/(250k+300k) *5v = 2.72v

If you use a cable with the data pins shorted together you effectively put the 43k and 75k resistors in parallel between +5v and data and also both 51k resistors in parallel between data and gnd. This will give you:

43k x 75k / (43k + 75k) = 27.3k effective resistance +5v to data
51k x 51k / (51k + 51k) = 25.5k effective resistance data to gnd.

Finally we can calculate the voltage on both data lines with this arrangement

25.5k/(27.3k + 25.5k) * 5v = 2.41v

You can see this is a bit lower than the TP is expecting but it might work for 2 reasons:
1. Resistors are notoriously vague in their value and can vary by +-5% quite easily.
2. The TP is likely to allow a reasonable range on the expected 2.72v

If you want an easy* way to get an iDevice charger to work with the TP, short the data pins at the TP end and cut data + on the charger end. This will make the Data - voltage (2.71v) appear on both Data pins which is what the TP wants from its own charger)

*easy is a relative term, good luck managing to short the pins on something as small as a micro USB plug


As ever, YMMV. I am not responsible for any damage you may cause.

PS. I'd like to say thanks to Wikitronic for his amazing circuit diagram tool at http://webtronics.googlecode.com Without the diagrams this thread would be much harder to follow.
 

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#24 ·
I'm not so sure I agree with everyone here regarding any Micro-B USB cable works with TP. My TP must be very finicky - the genuine HP ones and the ones from Monoprice work OK but the ones that came with a couple of cellphones do not - either for charging or for data USB connections. What could be related to this is that at one time, I thought I damaged the USB connector on the TP and sent it in for repair but when I got it back, I had some store bought that would not work and HP sent me a couple of their genuine ones and those work fine.

BTW, as far as I'm concerned, I don't think they ever repaired the problem and to this day connecting to USB is hit or miss. I only charge with a touchstone now and when I need to do large file transfers or WebOS hacks (like installing LunaCE recently) I need to take the TP out of its case and lay it flat and connect to the PC that way, otherwise I don't even hear a chime. I think the microUSB design and where it was placed (with no strain releif locks, etc) was one of the worst things HP did and was probably a contributing factor to why it failed after 2 months of its release.
 
#25 · (Edited by Moderator)
The bottom line is not all usb cables are created equal. Some cables are made as data only and will not charge a device. I've never heard of a usb cable made as a charge only cable. I've used several different cables besides the official HP TouchPad one and they all worked. Sorry to hear you have a usb port problem. Don't know how long it has been since you sent it in for repair, but it might be worth a try to get them to do it again since they have worked on it once.
 
#31 · (Edited by Moderator)
RolandDeschain79 and I had a conversation about some of these USB connector issues and since I have been inside the Touchpad and disassembled it completely I thought I'd share.
mpgrimm2 said:
I have not had any issues with the TP USB connector or it's cable 'yet'. I can say that the solder pads that hold the connector to it's circuit board are so very small that resoldering it for a better connection/stability is likely a non-starter for the majority of people without specialized "micro-min" soldering equipment (myself included). This leaves only 2 options (imo) that require the Touchpad to be opened up (using the iFixit Guide linked in my USB OTG Mod thread):
1) If the USB board is simply loose, reseat it's connector into the motherboard and re-tighten the 3 or 4 screws that hold it down.
2) Replace the USB controller board if one can be found on ebay, etc (about $30) and hope the part works.
There are 7 plastic clips that hold the TP screen to the back casing, as patient as I was, I broke 3 of them when opening it, but was able to superglue them back to the rear casing so they'd work again. I have yet to see new ones for sale.

I have several microUSB cables from Samsung, HTC, & LG phones, the Touchpad cable and three 12 inch cables from Amazon that all work as charge/data cables with the Touchpad and vice versa with the phones. I assume they all have the required 4 wires in them (+5v, Data +, Data -, and Gnd). Note, OTG cables add/connect gnd to the ID pin at microUSB end.
I haven't encountered any other cable types in a long time, ie "Charge Only" (+5v, Data pair shorted, and Gnd) except when hardwired to the wall plug, or "Data Only" (Data +, Data -, and Gnd).

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

[MOD] Self Powered USB OTG on the HP Touchpad! (v2 Full Size) 11-30-12
 
#32 ·
Small update.
Started having charging issues on my Touchpad where I could wiggle the cable and get it to charge. Turns out that the OEM TP cable was going bad, switched it out with the cable from my Logitech Harmony remote and all is good again.

Sent from my "Up all night, sleep all day" HP CM9 Touchpad
 
#38 ·
Like every1 else, I'm out of warranty at this point. HP's repair system in Texas is pretty dismal as you can't followup on a repair order over the phone and there's no paperwork.

Fortunately, I never had to ever use acmeuninstall or WebOS doctor. Nothing's ever been corrupted so knock on wood. The day when the usb port goes completely kaput and I don't get the 'chime' will be a sad day but I still think my TP will last a while..
Well, that sad day came around a month ago and there is now no USB symbol and/or chime coming through on my TP. So I decided to buy a used TP/touchstone off of Fleabay, and eventually restore with a Nandroid backup I maintain on my PC.

I will eventually either sell my TP or give it away as a gift. Question is on the android side, what's the best way to wipe everything, accounts included? My plan would be to do a factory reset, followed by installing JCSullin's CM10 experimental 4/18 ROM? On the WebOS side, I would just do a full secure erase which would pretty much take care of wiping out personal stuff from the SD card. Does that kind of erase remove preware? Remember, I can't ACME uninstall, doctor or do anything that requires the USB connection. Also, since the port is non-functional, how much should the price be marked down? It's still a good used 32G HP Touchpad.
 
#39 ·
Small update.
Started having charging issues on my Touchpad where I could wiggle the cable and get it to charge. Turns out that the OEM TP cable was going bad, switched it out with the cable from my Logitech Harmony remote and all is good again.

Sent from my "Up all night, sleep all day" HP CM9 Touchpad
Well, that sad day came around a month ago and there is now no USB symbol and/or chime coming through on my TP. So I decided to buy a used TP/touchstone off of Fleabay, and eventually restore with a Nandroid backup I maintain on my PC.

I will eventually either sell my TP or give it away as a gift. Question is on the android side, what's the best way to wipe everything, accounts included? My plan would be to do a factory reset, followed by installing JCSullin's CM10 experimental 4/18 ROM? On the WebOS side, I would just do a full secure erase which would pretty much take care of wiping out personal stuff from the SD card. Does that kind of erase remove preware? Remember, I can't ACME uninstall, doctor or do anything that requires the USB connection. Also, since the port is non-functional, how much should the price be marked down? It's still a good used 32G HP Touchpad.
Did you read the above posts and try a different USB cable? It's likely just a faulty cable.
 
#40 ·
Did you read the above posts and try a different USB cable? It's likely just a faulty cable.
No - this TP definitely has a faulty damaged connector. I kind of knew that early on when I bought it at the firesale and it dropped several times from my lounge chair with the cord plugged in. I must have tried at least 10 different cables which I could get it to work with a chime but 'unrecognized device' on the PC many times, and I must have forced these cables in the connector so hard at times that after 2 years, it's finally history and there's no chime at all. It won't charge either via the connector which is why I would sell it with a Touchstone.
 
#41 · (Edited by Moderator)
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#42 · (Edited by Moderator)
No - this TP definitely has a faulty damaged connector. I kind of knew that early on when I bought it at the firesale and it dropped several times from my lounge chair with the cord plugged in. I must have tried at least 10 different cables which I could get it to work with a chime but 'unrecognized device' on the PC many times, and I must have forced these cables in the connector so hard at times that after 2 years, it's finally history and there's no chime at all. It won't charge either via the connector which is why I would sell it with a Touchstone.
Ouchies, didn't realize that your TP had gone for a few tumbles. I've had trouble with connector and cables. I've moved around several TB of data while testing Fallout mods on the TP and damaged my connector in a similar way. It's still very loose and I kept fearing that it would break and i'd have to open up the tablet to fix it. Mpgrimm2 has a great guide for dissembling the TP; if you're handy with a soldering gun you might be able to fix a loose connection.

If you don't move around a lot of data the tablet should be functional enough with the Touchstone and WiFi File Transfer app. You should be able to sell it easily enough. If you can't do the fix some else might and get a bargain on a great tablet with Touchstone :grin:
 
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