Y-cable and USB-OTG: mutually exclusive

Joerg Reisenweber joerg at openmoko.org
Tue Apr 29 15:49:45 CEST 2008

Werner Almesberger schrieb:
> Andy Green wrote:
>> Well I didn't hear the answer to this 100mA default issue yet.  Maybe we
>> can find a pin that is active on the FTDI chip when it has a 500mA
>> descriptor enabled.
> If we include an EEPROM, we can program it to request 500mA. I don't
> know what the default is.
>> | It doesn't have to. All we need is some ADC that can probe what's going
>> | on there.
>> Probe what exactly?
> Charger presence, i.e., the ID pin. I don't think there's a safe way to
> also test whether D+/D- are shorted. (I.e., if the MPU or whatever does
> this test is connected to D+/D-, it could block access to the FT2232,
> and thus de facto brick the system.)

And here we are again, power over USB is just a pain in the a...
In the end, we probably are better off with a second fullfeatured USB


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