Umbauanleitung für den USB an der DM500Hd

#1
Howto Enable USB on DM500hd

Here is the guide to activate Usb controller on your DM500hd with a little hardware modification.
Warning: Removing resistors means you are going to VOID WARRANTY and everything happening since then will be at YOUR OWN RISK, no one will take responsibility for your own actions.
4fun: This guide is free and you can redistribute for every forums


Enabling USB port on DM500HD

On DM500HD there is a standard usb pinheader, but the usb controller has been fixed into a disable
state, because it misses an over-current protection on 5v pins (max1823 on dm800 for example) and
so it does not meet usb specs.
Removing a resistor (or two), you can fake the presence of such missing chip, but in case your usb
device makes a short, there will be no protection against flaming the main 5v mainboard regulator,
you can imagine what could happen. If usb specs requires an overcurrent protection, there must be a
good reason afterall.
Removing resistors means you are going to VOID WARRANTY and everything happening since
then will be at YOUR OWN RISK, no one will take responsibility for your own actions.


http://img121.imageshack.us/img121/8814/46412886.png


You can see here the standard PC motherboard usb pinheader with a standard PC usb bracket
connected. The bottom-right pin is in real disconnected, you have to make an hole into the PC
bracket connector to let it feet. On the rear panel of the decoder, there is a pre-cut window for a
single usb female connector, if you want a stylish job.


http://img521.imageshack.us/img521/3355/16529487.png


In my decoder there was only R1011 populated with a 0ohm resistor, but in case you have R1010
populated or both, you have to remove both. These are FAULTA and FAULTB signals that would
come from the missing max1823 usb power control switch, it’s enough to have one populated to
tell the Broadcom to disable the whole usb controller.


http://img521.imageshack.us/img521/1017/30627888.png


Looking at usb specs, the device that must handle the over-current protection is the hub, so, instead
of directly connecting an usb device, I would suggest to buy a good usb external-powered hub
which reports “over-current protection†on the specs, because the cheap chinese ones does not have
a dedicated power control circuit. Googling a little, hubs with Genesys GL850 chip seem good
candidates.


http://img171.imageshack.us/img171/6452/53445991.png


Thanks to pekogozolo
 
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