Walter,
I am afraid PU/PD settings are controlled by device tree, so you will
have to use them! You will be able to easily edit your current device
tree to change it, assuming you aren't using the default pin state. If
you are using the default pin state, then I would strongly recommend
getting a proper device tree file setup as it is not a good idea to
assume that the pin you are using will always come up in that state.
Cheers,
Jack.
On 22/03/2014 16:44, Walter Schilling wrote:
Good afternoon.
I am working on a project on the beaglebone white (as the blacks are out
of stock) and GPIO. I have tried two different setups, as shown below
for my pushbutton, and I am using the circuitco prototyping cape.
Configuration 1:
I have my pushbutton connected from GPIO0_26 to ground, and there is a
3.3K pull up resistor connected to 3.3 volts. I am assuming there are
no active pull up or pull downs in the system.
Configuration 2:
The pushbutton is connected in series from GPIO0_26 through the 3.3K
resistor to 3.3 V, and we are relying on the internal pull down resistor
to keep the pin low.
In either case, I am getting "phantom" interrupts when I poll for the
pin to change state. My gut feeling is they are brought on by noise.
I'd like to do away with the exteral pull up or pull down, but I don't
see any way to do that with the gpio driver from the documentation
at https://www.kernel.org/doc/Documentation/gpio/sysfs.txt, as it
doesn't seem to provide access to pull up and pull down configurations.
This leads to the following questions:
#1 Can someone provide me with the default pull up / pull down settings
for an input when exported with /sys/class/gpio?
#2 Short of going through the device tree (which seems horribly
complicated to simply change a pull up or pull down resistor setting),
is there an easy way to set of clear the PU/PD resistor through a c program?
I have seen multiple tutorials online dealing with this issue, but most
of them point to older kernel versions and when i try to follow them,
they break very quickly.
I am using the March 5, 2014 official beaglebone debian image.
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