Desire DC - microUSB - internal resistance

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Hi, I'm planning to build my own docking station and need some informations about the HTC Desire micro USB connection and the internal resistance of it!

The USB charger by HTC in Europe has 5V @ 1A max and I have original standard battery.

I've only one microUSB cable now (none to cut) and the connector is to little for my multimeter

Or is there a technical information data sheet for the Desire by HTC?! That would be awesome!!!

Thanks in advance for every hint!

I would definitely go for the official agreed specifications, as microusb is an EU standard agreed among manufactures. It would suggest that the pinout is also standardized and available. Google it.

Sent from my HTC Desire using XDA App

Originally Posted by _stefans_

I would definitely go for the official agreed specifications, as microusb is an EU standard agreed among manufactures. It would suggest that the pinout is also standardized and available. Google it.

Sent from my HTC Desire using XDA App

Hi Stefan,

Thanks for your quick answer, I checked the USB specifications at www.usb.org already and also the pinout. But I don't want to damage the battery. It seems that there are a lot of different chargers for all the microUSB smartphones.

I will build my own charger, so I cannot buy a standard charger for microUSB - That's because there will be some extra features and It's also a project to learn something for university

An E-Mail to HTC is out - hope they give me some technician sugar

If not, I'll buy a cheap micro USB cable, cut it and let my multimeter do the work...

Originally Posted by brianius

Hi Stefan,

Thanks for your quick answer, I checked the USB specifications at www.usb.org already and also the pinout. But I don't want to damage the battery. It seems that there are a lot of different chargers for all the microUSB smartphones.

I will build my own charger, so I cannot buy a standard charger for microUSB - That's because there will be some extra features and It's also a project to learn something for university

An E-Mail to HTC is out - hope they give me some technician sugar

If not, I'll buy a cheap micro USB cable, cut it and let my multimeter do the work...

if it helps at all i also use a micro usb cable from a Nokia without any issues so i would assume the pinout is the same and standard.

Originally Posted by coriron

if it helps at all i also use a micro usb cable from a Nokia without any issues so i would assume the pinout is the same and standard.

Thanks coriron! That's good to know

If somebody needs service manuals: http://www.mikechannon.net/page1.html (nearly all HTC devices, but Desire and Nexus One)
If anybody has the servie manual for Desire/Bravo or even N1 pls post it here.

The main problem here is, that i don't know the internal resistance while loading the battery. Maybe i can only check the battery with my multimeter, but I think the battery is not the only thing connected to the microUSB while loading...so there is a risk to damage something...and I don't want to buy a new Desire

edit: and of course I want the maximum loading power - and there are chargers between 4-12,5V/0,2-1A - (I've seen so far)

edit2: Okay, found some infos about the chargers - when plugged into PC there is communication through the 2 data channels (D- and D+) - When loading on charger it can happen that there is no charging (because of missing information through data channels) - so one has to connect D+ and D- with Gnd - like in most third party usb chargers! Then it should work. Maybe that helps someone later...

edit3: If someone is interested - one possibility to build a charger (european symbols!):

Originally Posted by brianius

edit2: Okay, found some infos about the chargers - when plugged into PC there is communication through the 2 data channels (D- and D+) - When loading on charger it can happen that there is no charging (because of missing information through data channels) - so one has to connect D+ and D- with Gnd - like in most third party usb chargers! Then it should work. Maybe that helps someone later...

Already had this problem a few couple of weeks ago with the car charger i got for the desire. All i did was open the charger up and short the 2 data pins (middle pair) together, not to ground, and it works fine and i now get the full current instead of the usb limit.

why don't you plug a normal usb jack into the htc original charger and measure everything you want to know?
it should be cheap (you must have some unused cables around) and you have enough space to use the mutlimeter.