[En-Nut-Discussion] Problems using Ethernut3 expansion port

[Ole Reinhardt]

Hi all,

for a project I need to use at least 14 I/O pins of the expansion port
as inputs to connect some buttons. I'd like to use a pulldown resistor
to GND and connect the button to VCC.

So far everything is ok, but I'm sonewhat confused about the internal
usage of the I/O pins. Reading
http://www.ethernut.de/en/hardware/enut3/ports.html

I think I could use 


P0, P1, P2, P3, P4, P5, P6, P7
P8, P11, P12, P18 abd P19 

for this purpose.

Now I'm a little confused about the internal connection of these pins on
the Ethernut3 board.

P3-P7, P8, P12 and P18 / P19 are connected to the cpld.

P18 and P19 should be possible to use when setting the jumpers the
correct way.

But what are the other pins are used for? 

It seems that the inputs are influenced by the cpld in some way. If I
use pulldown resistors > 20k-50k the pins are stuck at high after
pushing the connected button once. With lower resistors (10k) it seems
to work for this purpose, my oscilloscope still shows some influence by
the cpld. Are'nt thos connected but internaly unused cpld pins
configured as tri-state?

Only the pins P0, P1, P2 and P11 work as expected.

Any suggestions are wellcome.

Regards,

Ole Reinhardt

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