USB Cable Mod for generic USB adapters and Touchstone Dock

[Supra]

Hi all, I was searching around the web and found this thread...

What i'm trying to do is, take my exitsting car charger and, cut the connector end off, solder on a micro-usb connector and see if I can use it to charge my Pre in the car?

What are your thoughts on doing this?? Thanks.

BTW~ where to buy the micro usb connectors anyway?

[deligator]

I am looking to do this from my PC. Is there a driver that will allow those two pins to be shorted so that you would only have to make a mod to the USB controller Hub that you are using?

[hmayesh]

I too wanted to charge my pre using my laptop USB witha touchstone. After reading these posting, I decided to short the comunication wires of the usb. I still wanted to use my monoprice micro usb cable for data transfers. So instead of modifying that cable, I got an unused 6 inch extension cable from my desk. Cut open the connector cover at the end where I would connect the micro usb cable. Then I cut the two middle wires. Next I pinched the two stubs together to short the 2 and 3 pins together. I plugged up my touchstone, and now my phone charges at the 1% per minute I'm used to seeing.

So either my dell laptop is giving me more than .5 Amp (which I doubt) or the touchstone just needs to see those two pins shorted.

I hope this helps

[wekya]

I've been in several threads, and am still not clear. Are all micro USB cables created equal? I seem to be getting different performance when using my 2$ cheapo cable than my Palm cable for charging from wall wart, and computer. I haven't investgated data speeds yet. I'm gonna have to mule a touchstone here to Taiwan and it ain't gonna be easy, so maybe I need to get extra cables too? I was just gonna buy more of these cheapo cables and seed them in all my regular haunts for charging the woefully underpowered battery. Tonight I noticed the cheapo cable was really not charging, out it on the Palm cable (both from the same Palm wall wart) and it charged quickly.

Help!

[Staedtler]

To summarize, I think the only facts we've deduced are thus:

- The Palm wall charger provides 5 V at 1000 mA. It shorts pins 2 and 3 of the USB connection together, which tells the phone it's a "fast charger" (ie. it provides 1 A of current). Shorting those pins prevents any data from going through the cable, but that's irrelevant to the wall charger.
- The Touchstone requires 5 V at 1000 mA to function correctly, and pins 2 and 3 must be shorted.
- If you manually short pins 2 and 3 on a Touchstone while providing less than 1000 mA, the Touchstone will do crazy things, the least of which is "not work."
- The USB power standard for computers is 5 V at 500 mA. This will slowly charge the phone, but will not drive a Touchstone.

Now here's some speculation of my own: some newer computers provide more current on the USB ports than the standard 500 mA. This would be because we're seeing more and more USB-powered devices on the market (including rechargeable devices like phones and MP3 players, but also portable storage, optical drives, network adapters, etc.). But obviously your computer is not shorting USB pins 2 and 3 -- it needs those pins to transmit data. So instead, we can modify the cable to short pins 2 and 3 and get the same effect. This seems to be what hmayesh described above.

In addition, I've encountered several devices that come with what appears to be a USB "splitter" cable. This cable has two male USB-A connectors (that plug into the computer), and one female A connector. I've seen them included with both a 2.5" hard disk enclosure and a GSM cellular Internet stick. The cable is allegedly to provide extra power if the device doesn't work correctly on its own. It seems to me, then, that this "splitter" combines the current from two separate USB ports, providing 1000 mA or more to the device.

I'm going to have to test this out myself when I get home, by shorting pins 2 and 3 on a micro-USB cable then plugging it into the splitter. If these splitter cables are available for purchase on their own, it could be the answer to powering a Touchstone and/or rapidly charging from any computer.

[Staedtler]

Originally Posted by wekya

I've been in several threads, and am still not clear. Are all micro USB cables created equal? I seem to be getting different performance when using my 2$ cheapo cable than my Palm cable for charging from wall wart, and computer.

I believe it's just the quality of the cable. USB signals are very sensitive to the length of the cable (many devices max out at 6 feet), which would be due to the conductivity/resistance of the cable. Cheaper cables just won't conduct as well as expensive brand-name ones. Anyone, please correct me if I'm wrong.

[Staedtler]

And this is my last post for now, I swear:

Does anyone know whether the Palm can report how much current is coming in on the USB port, or otherwise how fast it's charging? I'm aware of dialing ##DEBUG# in the phone, where you can see the current battery voltage, but I'm too lazy to watch the rate of increase and somehow calculate power input from that.