7 Nov
2011
7 Nov
'11
12:17 p.m.
On 7 Nov 2011 at 11:40, David Griffith wrote:
You might want to consider a simple modification that
reduces the
current draw. Just add some pullup resistors to the clock and data
lines. I think someone else mentioned this too. See
http://ps-2.kev009.com:8081/ohlandl/keyboard/modify_keyboard/Model_M_M
odifications.html for a discussion on that mod.
I have to admit that I don't understand how the mod reduces current
draw--the way the keyboard is interfaced is with open-collector (open
drain), devices. Adding pullups would seem to *increase* the power
drain.
That being said, it's probably okay to power the keyboard separately
from the USB adapter, as long as the only pin shared
between the USB
interface and the power supply is ground. I suspect that a simple
adapter cable that does not feed the +5 supply to the USB converter
can be easily constructed for this purpose.
I have no idea if this will improve matters, however.
--Chuck