[MinnowBoard] 1-Wire Support like Raspberry Pie GPIO4 at MAX

[Markus Maier]

John Hawley <john.hawley at ...> writes:

> 
> On 11/10/2014 12:53 PM, Bastian Wassermann wrote:
> > Hello, i am really new to linux and the whole single board computers. I
> > have read much about the support for the 1-wire protocol at raspberry
> > pie on GPIO4. Is there something similiar to the minnowboard max? I dont
> > know what is special about that GPIO4 at RPi. Could someone explain
> > whether its possible and is there also a 4k7 Ohm resistor needed?
> 
> Doing some quick digging the answer is we should be able to support it.
>  W1 (one wire) has a gpio driver, which should work on the MinnowBoard
> MAX.  It won't exactly work out of the box, as it has the same problem
> that spidev has, in that we don't have quite the same system descriptors
> as the Pi.  That being said a board file or a dsdt shouldn't be hard to
> add, and I'll see if I can find a sensors to pick up so we can add
> support into the extras repo for W1 on the MAX (from a software
> perspective).
> 
> - John
> 

I also had a look at this some time ago and I'd like to help setting up and
testing this for the MinnowBoard MAX. As Bastian mentioned, when using
Raspbian the implementation on the RPi works very well out of the box.

My findings on the software side (with my limited knowledge) were, that the
w1_gpio module can be loaded in Ubuntu, but just does nothing. I guess, the
platform file for the MBM is missing here so the module just doesn't know
what to do. This might be the one we need to create as John just said.

I remember some discussion going on that GPIO4 is hardcoded somewhere in the
source code but can't remember if this was RPi specific or not. There is an
implementation of w1-gpio-custom and also some patches for the original
module to take the GPIO pin as a parameter which is much more flexible. I
had a quick shot at these but without the platform file we won't get far.

Does anyone have a how-to which describes what to do to get this running,
how to create the platform file and how to throw it all together?

- Markus