How To Hack A USB Charge Cable

Darren · Last edited by Darren on Fri Apr 22, 2011 9:13 am; edited 1 time in total

This issue has been discussed in our forums a number of times and affects devices from quite a number of manufacturers. When connected to the PC they mount as a disk drive and when connected to the supplied USB car charger they will charge and function as normal.

But, when connected to a third party 12v USB charger they act as if connected to a PC and refuse to charge or to offer the normal GPS related display and functionality.

This occurs because the manufacturer has chosen, for reasons best known only to them as USB is supposed to be a standard, to short USB pins 4 and 5. The device looks to see if pin 4 is grounded and if not, it switches to USB disk mode.

It's naughty because there is no good reason for doing this. A correctly wired device should be able to mount as a disk and charge when connected to a PC without this subterfuge and all it achieves is to prevent you from using third party chargers.

A Hackaday reader investigate as this problem affected his Magellan and, having found the cause, set out to hack a standard USB cable and ground the unused pin 4 to pin 5 on the microUSB plug. Now he can use the cable with any USB charger.

He has posted the Hack with an explanation on Flickr and whilst it may not be for everybody, anyone who has a spare USB-MiniUSB cable, a steady hand and a soldering iron may want to give it a go.

This issue affects Magellan, Mio and Navman devices and I'm sure Garmin has this issue with some models.
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Darren Griffin

smartroad · Occasional Visitor Joined: Jun 17, 2005 Posts: 28

Just as a thought, before having a go at manufacturers, is this done in case the device draws more then the 500mA a standard usb port is specced the provide? Like I said, said just a thought.

smiley1081 · Occasional Visitor Joined: Mar 08, 2006 Posts: 51

I have exactly the opposite problem.

If I connect my Nuvifone A10 to a computer using its cable, it is recognised by the computer as a USB device, if I use a third party cable it can be charged but not used as a USB device.

Could it be that this is caused by the same connection between pin 4 and pin 5?

BigPerk · Posted: Fri Apr 22, 2011 10:23 am Post subject:

Well, I seem to have had a lucky escape! I didn't know about this when I bought a 3rd-party charger to use with my Navigon Rolling Eyes

. Thank goodness that at least they don't have a Dirty-Tricks department Very Happy

.
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David
(Navigon 70 Live, Nuvi 360)

Darren · Posted: Fri Apr 22, 2011 11:16 am Post subject:

Andy_P · Posted: Fri Apr 22, 2011 11:42 am Post subject:

wrinklyninja · Occasional Visitor Joined: Sep 21, 2006 Posts: 51

I had exactly the same problem with my Palm Treo Pro. The fix of shorting out the data pins worked a treat. The only comment I would make is make sure that your 3rd party charger delivers the same output as the OEM eg 800ma etc

treeboa · Occasional Visitor Joined: Oct 25, 2007 Posts: 2

same problem with this device using the supplied usb cable and a third party charger, in this case a 2000ma one, bloody annoying really as the charge cable is not a standard easy/cheap replace cable, you can by pass it with a few button presses but still it smacks of `dealer part only`

dvd8n · Occasional Visitor Joined: Mar 08, 2009 Posts: 4

This isn't dirty tricks, this is the new USB compatible charger standard.

The idea is that if a device is connected to a computer then the USB's data lines are not shorted. The device knows that it is connected to a computer and, while it charges, it knows to draw a max of .5 amps. And it can talk to the computer.

However, if a device is connected to a charger then the data lines are shorted. The device knows that it is connected to a charger and, while it charges, it knows that it is a standards compliant charger, it can draw a lot of current as it is connected to a charger, and it charges to a max of 2 amps, charging much faster.

Now this is all fine until someone tries to charge a new device with an old charger. The device, as the lines are not shorted, thinks that it is connected to a computer, tries to talk to it and gets confused, and often discharges itself faster in its communication attempts rather than charging.

Now you can short the data lines on a USB cable. Or you can even crack open the charger and short the lines there. And this is fine - it will work. But there are two warnings. The charger must be capable of supplying 2 amps. And you must never use the modified cable on a computer as it will draw more than the .5 amps that a USB port is rated at and potentially blow the power supply.

Or you could stop being so tight and buy a charger to the new standard. You will find that you need it more and more over the coming years as more devices become compliant. Wink

BigPerk · Posted: Sat Apr 23, 2011 5:49 pm Post subject:

So do you know what the new USB standard is (ie ISO, ..., Number) dvd8n? It would be a good idea to be able to check for compliance when purchasing off, eg, Amazon.
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David
(Navigon 70 Live, Nuvi 360)

dvd8n · Occasional Visitor Joined: Mar 08, 2009 Posts: 4

wrinklyninja · Occasional Visitor Joined: Sep 21, 2006 Posts: 51

I agree with the sentiment that it would be nice to know what you are buying. I bought 3 different car chargers for my Palm Treo Pro (all of which claimed full compatibility) and none of them worked. It's OK to say don't be tight and buy an OEM part but the Palm charger is over £20 and is crap. I know because I had one.

tcs17_tim · Posted: Sat Apr 23, 2011 8:00 pm Post subject:

Could this be why my pocket pc charges from the USB port on my pc but will not charge from the USB port on my tecknet battery charger.

AliOnHols · Pocket GPS Verifier Joined: Oct 15, 2008 Posts: 1941

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dvd8n · Occasional Visitor Joined: Mar 08, 2009 Posts: 4

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