[coreboot] LPCflasher Project

[Joseph Smith]

On Sat, 15 Nov 2008 21:26:05 +0100, Peter Stuge <peter at stuge.se> wrote:
> Joseph Smith wrote:
>> Anyone know if USB ports have power feedback protection.
> 
> All the details are in the USB spec. IIRC electrical is a separate
> chapter.
> 
> 
>> What I mean by that is if I use the LPCflasher as a inline flasher
>> with a PLCC32 socket plug,
> 
> I don't understand this. Do you mean a socket or a plug?
> 
Both, a socket on top of a plug that is also connected to the LPCflasher.
If I power on the motherboard it is going to supply voltage back to the
LPCflasher, right?
> 
>> flash the chip
> 
> Flash which chip?
> 
Any LPC or FWH.
> 
>> and then power up the motherboard, I don't want the VCC's from the
>> motherboard to short out the flasher and or the USB port from the
>> host PC.
> 
> Make sure GND is connected across and you should be OK.
> 
Yup.
> 
>> The 3.3V regulator I am using has a internal diode so I am not so
>> worried about that. I am just worried about the power source 5V
>> USB. I could always use a Schottky diode that will only drop the
>> voltage by .6V, but I don't know if 4.4V will suffice???
> 
> Suffice for what? Look at the documentation for the regulator you're
> using to see what input voltage it needs.
> 
> 
I wasn't really ready to release this yet, because the power part is still
a work in progress but it will be the easiest way to explain this. See the
diode I have above the regulator? I put that there so power is not flowing
back to the USB port of the PC doing the flashing when you power on the
motherboard that just got flashed. My question is if I take out that diode
and you power on the motherboard that just got flashed is power going to
flow back into the USB port and damage it? And if I leave the diode it is
going to drop the 5V by approx. half a volt. Will I still be able to flash
5V chips at 4.5V? Does that make sense?

-- 
Thanks,
Joseph Smith
Set-Top-Linux
www.settoplinux.org
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