Dave wrote:Since we have no way of knowing what extensions may be added in future, it just seems conservative to spend the 50 cents to provide separate regulation for them. I don't know if the Q68 has one or two LM1117-3.3's but even with two, and a heavy consuming keyboard and mouse that could leave as little as 600mA available for every extension.
Let's be more precise. You were talking about power from SER handshake lines at first. This is 5V not 3.3V, just the protection resistors are too large for your application.
Keyboard and mouse are also powered with 5V! They do not take away from the limited 3.3V.
There are two 3.3V regulators, but one is reserved for video, to ensure highest picture quality.
That said, I don't find a separate power supply a bad idea, that makes your devide more universal. Does ist it still include the
option to draw 5V power from serial handshake lines?