[Libre-soc-bugs] [Bug 746] I2C needs an Open Drain IO Pad

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=746

--- Comment #2 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Cesar Strauss from comment #1)
> It seems that Open Drain can be implemented by a constant zero output, and
> switching the tri-state/direction/oe control signal (1=tri-state,
> 0=push-pull to ground).

interesting.  this would however need to be done by a mux, where
"if the output is zero, also flip the IOpad out-enable to zero"

which, now that i think about it, can be handled by the GPIO
subsystem.

my only concern is: timing. but, hey, Open Drain does not switch
quickly anyway.  I2C maxes out at 400 khz.

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