USB Cable Mod for generic USB adapters and Touchstone Dock

[gostate]

If you choose to follow these directions, do so at your own risk. You could fry your Touchstone dock, usb adapter or overheat and start a fire if you're not careful. This is the definition of a dirty hack, but does answer some questions about the charging.

The Palm Touchstone dock seems to look for chargers that support the new USB Fast Charging standard. This standard allows for simple, cheaply produced chargers to charge devices more quickly. (Credit: Wikipedia article on Universal Serial Bus)

As a way of keeping things cheap, these Fast Chargers indicate their ability to provide higher than normal current to the device by shorting the D+ and D- pins on the USB cable together. This way the charger can signal to the device that it can provide the higher current without any special electronics to communicate with the device, which would raise the manufacturing cost. This is the center two pins in a standard USB A cable.

To test this, I verified this behavior with a multimeter. Sure enough, on the Palm chargers, the two middle pins are tied together. On the USB chargers that don't work with the Touchstone, there is no continuity between the two middle pins.

As an experiment, I decided to sacrifice a cheap Micro USB Cable (thanks Monoprice!) to see if one could make a cable that works with regular USB chargers. I cut the insulation off around the cable near the A connector side, clipped the White and Green wires and tied them together (The side connected to the Micro USB, not the charger side). I then plugged my modded cable into the adapter from my old iPhone which did not work before, hooked it up to the Touchstone, set the Pre on top and it lit right up and began charging. Obviously if you were to use this as a permanent solution you should soldier the wires together and make sure everything is properly insulated with tape and heat shrink.

I probably wouldn't have been willing to try a hack like this if it required plugging this hacked up cable into the actual phone, but I was willing to try it with the Touchstone dock in the middle so I could satisfy my own curiosity.

If you try this (and I suggest you don't), remember that your USB cable will never again be good for data transfer again. Also, if you use a USB adapter that is not capable of supplying the full 1 amp of 5V DC (like Palm's does), you could burn up your adapter and/or start a fire.

I've taken some pictures, but I'm assuming since this is my first post I'm not allowed to post them. I'll try and get them up somewhere else tonight in case anyone's curious.

[realistdreamer]

At least you've satisfied some curiosity.

[NickDG]

Great work man!

[casonbang]

I did some research into this and I believe Wikipedia is talking about the USB Battery Charging Specification 1.0 (Which is now up to spec 1.1)

Here's the spec:
http://www.usb.org/developers/devcla...arging_1_1.zip

Some tests of chargers that meet the spec (only tested mini-usb?):
Neo USB charger specifications and compatibility list - Openmoko

I wonder why they aren't making this information easier to find? If Palm's intention was additional revenue from chargers, why not just make the Touchstone wall adapter proprietary altogether?

[gostate]

Originally Posted by casonbang

I wonder why they aren't making this information easier to find? If Palm's intention was additional revenue from chargers, why not just make the Touchstone wall adapter proprietary altogether?

It's hard to say, I'm guessing that it's not a big deal to them one way or another. Follow the standard, if people figure it out, great. If not, make money on chargers.

I do have to give them props for following the standard way of doing it, unlike some other manufacturers have had a habit of doing (Looking at you, Motorola).

[northward]

Originally Posted by gostate

I cut the insulation off around the cable near the A connector side, clipped the White and Green wires and tied them together (The side connected to the Micro USB, not the charger side).

OK, but what do you do with the remaining two ends of the green and white wires, the ones leading to the A connector?

[gostate]

Originally Posted by northward

OK, but what do you do with the remaining two ends of the green and white wires, the ones leading to the A connector?

Leave the insulation on them and/or cover them up as best you can, they aren't connected to anything.

[northward]

Well, then, either the Mulit-Function Charger sold by Seidio doesn't output the 1A it claims to, too much of that 1A goes to the spare battery charger, or I somehow screwed up doing something so simple as wrapping two wires together. Whatever the reason I was unsuccessful in using that Multi-Function charger with the TS.

[wprater]

The iphone chargers that I have all seem to work and are rated at output 5V 1Amp

Are you saying there is an issue with the cables or charger that we should be using with the Touchstone?

[wprater]

This is only for the Touchstone, not charging the Pre in general, correct?

[Carioca_FL]

I may be missing something (and looking at the time, I probably am... ) but if you are looking to use a generic microUSB cable with your existing TS and AC adapter (ie: if you lost the cable that came with the Pre, like me) all you need is a generic cable (monoprice) and file down the microUSB plug until it fits in the microUSB slot in the back of the TS.

I've done it and it works great.

[wwood_98]

Originally Posted by Carioca_FL

I may be missing something (and looking at the time, I probably am... ) but if you are looking to use a generic microUSB cable with your existing TS and AC adapter (ie: if you lost the cable that came with the Pre, like me) all you need is a generic cable (monoprice) and file down the microUSB plug until it fits in the microUSB slot in the back of the TS.

I've done it and it works great.

No, the OP is talking about modifying a generic (Monoprice) cable, then using it with an AC adapter that is capable of supplying 1A current.

[jhoff80]

So out of curiosity, if the OEM Pre cable has the two pins shorted and 'isn't capable of data transfer", how come it's capable of data transfer?

Edit: Wait never mind, you're saying it's that way in the charger but rather than hack up a charger you're just modifying the cable.

I also wonder if the Palm OEM car charger has those two pins shorted out or not.

[NickDG]

Originally Posted by jhoff80

So out of curiosity, if the OEM Pre cable has the two pins shorted and 'isn't capable of data transfer", how come it's capable of data transfer?

Edit: Wait never mind, you're saying it's that way in the charger but rather than hack up a charger you're just modifying the cable.

I also wonder if the Palm OEM car charger has those two pins shorted out or not.

It must.

[gostate]

Originally Posted by jhoff80

Edit: Wait never mind, you're saying it's that way in the charger but rather than hack up a charger you're just modifying the cable.

Yes, that's exactly right. The more correct thing to do here would be to open up a charger and connect the two middle contacts in it, but the cable seemed easier/safer.

[NickDG]

I just performed this hack. Before when I would plug in the Pre to charge, it would take a few seconds then start charging. Now it starts charging instantly. I am shaving down the cable now to try it with the Touchstone.

With the monoprice wall charger.

[NickDG]

The Touchstone didn't work but got further than without the mod. Before the cable mod it wouldn't register charging at all, now it does the on/off charging dance.

So the extra juice is there, but not enough for the Touchstone it seems.

[dbett]

I wonder if this is why the Boxwave's Pre cables have a special "charging" Micro-USB plug, in addition to the normal "sync" plug.

See the retractable version of their cable here:

miniSync - Pre Retractable Cable / Palm Pre Retractable Cable / Pre USB Cable / Palm Pre USB Cable

[draven76]

Great, now it seems that we've explicitly identified the standard type of chargers that should work with the touchstones (i.e. fast chargers). As an alternate to the marked-up palm chargers/cables, does anyone know anywhere where we could buy microUSB fast chargers?

[Nurgling]

Interesting read here with some peoples comments concerning hacking the mini usb pin outs. and using differing resistors to achieve varying amperage.

h t t p : / / pinouts.ru / CellularPhones-A-N / razrv3_charger_pinout . shtml

cut/paste much of the text here:

RAZR V3 will not charge by simply supplying 5V through USB (it's possible to use common USB cable for charging if you are using Motorola special PC driver software).
Motorola uses the pin between Pin #3 and #4 (Pin X) to sense what device is attached to the mini-USB port. Shorting Pin #3 to #2 and #X causes the phone to go into handsfree/carkit mode and the LCD backlight will ignore timeout settings and stay on.
Shorting pin X to pin 2 and to pin 4 via R=200KOhm causes the phone to go into charge mode.

MOTORIZR Z6tv - In Order to make your PC charge your phone through a usb cable w/o installing any special drivers or software: Short pins 2 and 3, then put a 200K Ohm resistor between pins X and 4.

- The phone supplies ~2.14Vdc to pin X before anything is plugged into it. It needs to be dropped 1V to approx 1.16Vdc. Putting a 200K Ohm resistor between Pins X and 4 will bring that voltage down to around 1.16Vdc.

- The wall charger has pins 2 and 3 shorted together. Not sure if it's a safe practice shorting the USB DATA lines together on your PC, so do at your own risk. However, it does work on my terminal with out any ill effects.

Comment by Darrin
A standard Motorola USB charger puts ~1.4vdc onto the x pin of the mini USB plug. A 200k resistor between pin 2 and 4 produces ~1.9vdc on the x pin. This works for Motorola Q (which works from ~1.2vdc to ~1.9vdc), but not for Razr V3m. I had to lower the resistor to 165k. This produces ~1.5vdc and allows the charger to become authorized.

Comment by Andre
After many trial and error, the working pinout for my RAZR V3C was to short 2 and 3 THEN Short X and Gnd with a 200KOhm resistor. Work good on my unbranded USB car charger and with a PC without any driver installed.

Here is a schematic :

1 _____________ +5V ____________
2 _______,
PHONE SIDE 3_______/ USB / Power Supply side
X_______/\/200Kohm /\__,__ GND ___
4___________________/

Comment by Eric

Andre's schematic also works for the motorola IC502. I used a 220kohm resistor(that's what I had laying around). Thanks Andre.

Comment by kaputnik

Andre's schematic also works for the V3x. According to the spec sheet for the Enhanced Mini USB interface circuit, shorting pin 2 to pin 3 (the data lines) and putting a resistor of 200kOhm on the ID pin x to pin GND will put the phone into "Dumb Mid-Rate Charger (500mA)" mode with 1.225 volts on pin x. Putting a 440kOhm resistor on pin x to pin GND will put the phone into "Dumb Fast Charger (1.25A)" mode with 1.68 volts on pin x.

Comment by Alex

I just broke my RAZR V3i original car charger and it have the following: 1 +5V, 2 shortened to 3, X goes to GND via 440kOhm.

Comment by Tom Maneiro

I have tested with a 260K resistor (i only had these in this range) with a standard Motorola wall-wart charger (the MiniUSB plug on it was broken), and it works with V3c, V3m, U6, U6c... but not with my K1m (it only says "Unable to charge").