On 4 September 2016 at 19:59, Jan Kandziora <j...@gmx.de> wrote:
> Am 04.09.2016 um 19:08 schrieb Colin Law:
>> ...
>> To summarize then, for parasitic mode I should not need an external
>> strong pullup and should be able to use just a 1.5k pullup and to
>> specify
>> dtoverlay=w1-gpio,gpiopin=4
>> and
>> sudo modprobe w1-gpio pullup=1
>>
>> With in addition the 3.3 to 5V level shifter as in your first post if
>> any devices on the bus need 5V
>>
> Yes.
Sorry, I need yet further clarification on this. I have been trying
to get to grips with device tree and (on pi with raspbian jessie) in
/boot/overlays/README it says
"Device Tree makes it possible
to support many hardware configurations with a single kernel and without the
need to explicitly load or blacklist kernel modules."
which I think means that it should not be necessary to use modprobe
w1-gpio or to put the module in /etc/modules.
Also for w1-gpio it has
"Name: w1-gpio
Info: Configures the w1-gpio Onewire interface module.
Use this overlay if you *don't* need a GPIO to drive an external pullup.
Load: dtoverlay=w1-gpio,<param>=<val>
Params: gpiopin GPIO for I/O (default "4")
pullup Non-zero, "on", or "y" to enable the parasitic
power (2-wire, power-on-data) feature
Does this mean I can (should?) use
dtoverlay=w1-gpio,gpiopin=4,pullup=y
and remove the modprobe command?
Colin
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