Norman Dunbar wrote, on 23/Aug/12 18:37 | Aug23:
On 23/08/12 16:26, Tony Firshman wrote:
I find mine *does* need an external power supply when running some
keyboards.
Yes, the two USB ports are poly-fused to 100mA each. Some keyboards
and/or mice draw more so the fuses kick in and increase resistance (why
am I telling you this?) reducing current. This causes the keyboards to
act like a QL with a dicky membrane, and misses keys or start
auto-repeating at a huge rate.
Interesting. Yes I knew about the fuses, of course, but not the capacity.
However my Apple keyboard is fine when Pi is run off a USB charger, but
not off the monitor usb port. The issue must be the monitor power
limit, not the polyfuse limit. Do these polyfuses degrade at all I wonder?
Tony
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