On Thu, 31 Jul 2008, akacairo wrote:
> I am facing a weird problem:
>
> For tests during development of my software I built a simple circuit
> on a Breadboard to test DIO I/O signals.
>
> If I sent a output signal, everything is fine, my test LED turns on.
> But I press an input switch, the signal has a variable delay between 0
> and about half a sec.
This sounds like your software is reading cached DIO input values.
Make sure your pointers are declared volatile, and make sure your /dev/mem
open call has the O_SYNC option.
> The switches are not debounced, I wanted to do that in the software. I
> wrote a loop that sends the input signal inverted to the output, so I
> was expecting some jitter at the LEDs.
>
> But instead of this the LEDs turn on, but with the described delay.
> That happens in TS-Linux as well as in Debian, so I suppose it's not
> because of other processes...
> Then I made a simple bridge between GND and an input line to check if
> the board's capacity is the reason - same result.
>
> I'm a bit out of ideas now, any hint would be great,
>
> Albrecht
>
>
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