[PD] problem with arduino digital ins - Pduino-0.5beta8 / Firmata 2.1

Ingo Scherzinger ingo at miamiwave.com
Wed Jun 30 16:42:50 CEST 2010

I suppose you're right about the different types of controllers being
attached to the arduino. It's definitely better to keep the pullup resistors
off as default!

I think it just needs an extra line on the help patch so people would know
about this "feature" and how to use it.


> Von: Martin Peach [mailto:martin.peach at sympatico.ca]
> Roman Haefeli wrote:
> > On Wed, 2010-06-30 at 14:12 +0200, Ingo Scherzinger wrote:
> >> Hi Roman,
> >>
> >> this solution is working also. So in this case it's not really
necessary to
> >> change the firmata itself. Anyway, I would prefer to have this
behaviour as
> >> the default behaviour, i.e. included in firmata. At least all of this
> >> should be documented.
> >
> > Actually, it is here:
> > http://www.arduino.cc/en/Tutorial/DigitalPins
> >
> > It's not firmata exposing this functionality, but the arduino. So I
> And shining through that is the actual microcontroller. It's useful to
> read the data sheet to see what is possible:
> http://www.atmel.com/dyn/resources/prod_documents/doc8271.pdf
> > think it's correct that Firmata handles it transparently, so that from
> > Pd you are still able to decide yourself, whether you actually want that
> > pull-up resistor or not.
> >
> > Enabling it per default is _not_ a good idea, since there are many
> > applications, where you deliberately want the pull-up resistor not to be
> > enabled. Imagine a sensor with a very high impedance (for instance, an
> > LDR in series with a fixed 1 MOhm resistor), with the pull-up resistor
> > activated the input would always be HIGH, because the internal resistor
> > would brutishly pull the voltage up.
> Or if the pin was connected to a relay or something. This is why most of
> the pins default to high-impedance input after a reset.
> Martin

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