Why do you need a valid driver to charge a device via USB?

Question

_{Disclaimer: While this question is about my smartphone and hence may be considered off-topic, I'm hoping the more general issue (which could apply to other USB devices) can be answered in this forum.}

My work PC was recently upgraded to Windows 7 64-bit edition.

I have a Palm Treo 680 smartphone and on the previous operating system (Windows XP) it would always trickle charge via USB when I had it plugged in.

However, there is no updated Palm Treo USB driver for Windows 7 64-bit edition, which means I cannot synchronise it via USB (I have to used Bluetooth instead).

One thing I have noticed is that when I plug it in via USB to my Windows 7 computer, it won't even charge. I'm wondering why a valid USB driver would be required for this; shouldn't the charging be occurring at the physical layer of USB, where a driver wouldn't be necessary?

I have a Windows XP virtual machine installed, and when I explicitly "attach" the phone to the virtual machine via the USB menu, it commences charging.

Answer 1

By default, a device is only allowed to draw up to 100mA from a USB port, and must negotiate with the host if it needs to draw more.

Maybe your device is implemented in a way that does not allow for power negotiation until a driver has taken control of it ?

Answer 2

I had the same problem but I found that a company named Aceeca has released new x64 drivers for Windows 7 which will work with your Treo 680.

64-bit Windows USB Drivers for Palm/Garnet OS http://www.aceeca.com/downloads/download_overview.php/cPath/1/downloads_id/13

Troubleshooting/install guide http://www.aceeca.com/products/pub/english/Troubleshooting_USB_driver_installation_on_Windows_7_64-bit.pdf

Answer 3

I know that some devices cannot be charged unless the driver software is installed on the computer. Some MP3 players from Creative actually do that. And the Creative ZEN will not charge using a regular USB charger. You need to buy the charger from the company. However, if the pinout is not hacked by the device, a regular USB charger could do the job. Or make yourself a special adapter by only keeping the power pins on an existing USB extension.

You should find the USB specs on the internet. Google for USB CABLE SPECS

JF

Answer 4

My Sony ebook (PRS-700) does that kind of thing. It simply will not charge off of USB unless it has a fully established USB session with an actual computer. Those wall chargers with USB ports won't do the trick. And yet, my iRiver Clix2 media player charges just fine off of that same wall charger. It varies by device, for the reason B0fh pointed out.

Answer 5

Perhaps you should look into a "charge only" USB cable adapter, like this one from iGo.