Re: [Gumstix-users] Help setting up a timer in an overo fire

[Markus S. <msv...@ae...>]

Hi Roque,

Next try this:
ls /sys/class/gpio/gpio145/

to see what is available for that GPIO.

I don't have the time right now to make a complete example, but it won't 
be hard for you to follow some steps on your own. Here is what I suggest:

Have a look here, it basically explains step by step how to set up a 
gpio for input:
http://gumstix.org/software-development/how-to/250-gpio.html


Next, to use the edge interrupts, you need to read this carefully:
https://www.kernel.org/doc/Documentation/gpio/sysfs.txt

In your system start-up script (e.g. /etc/init.d/rcS) you could do 
something like this:

# Set direction of gpio 145
echo in > /sys/class/gpio/gpio145/direction

# Request edge interrupts, rising and falling
echo both > /sys/class/gpio/gpio145/edge

You could also do this from a C program, by opening the files and 
writing the strings to them. A more permanent way is to set up the gpio 
is to patch your kernel (board_overo.c file) to set up the gpio(s).

Then, in your C program you can do this:

int gpio = open("/sys/class/gpio/gpio145/value", O_RDONLY);

Then, you can set up a loop that uses poll() or select() to wait for 
events occurring on the gpio file descriptor. This would probably have 
to be run from a separate thread.

An alternate and less CPU efficient way, that does not involve poll() or 
select(), would be to set up a loop that periodically (e.g. 10 or 50 
times per second) checks the gpio value, and takes action when the value 
changes.

Hope this helps you start.

Regards,
Markus




On 03/18/2014 04:04 PM, Roque Lora wrote:
>
> Hi Markus,
>
> Could you give me a small example of using edge (for rising and falling)?
> I have these gpio available:
>
> *gpio15**gpio168**gpiochip160**gpiochip64*
>
> *gpio144**gpio16**gpiochip0**gpiochip192**gpiochip96*
>
> *gpio145**gpio164**gpiochip128**gpiochip32*
>
>
> I want to use the gpio145 (I am not using and LCD).
>
> That would be of great help.
>
> Regards
>
>
> Hi Roque,
>
> You can configure GPIO pins for input or output:
> http://gumstix.org/software-development/how-to/250-gpio.html
>
> Additional useful info can be found here:
> https://www.kernel.org/doc/Documentation/gpio/sysfs.txt
>
> If you log into your Overo command line, you can see what GPIOs you have
> available by running the command:
> ls /sys/class/gpio
>
>
> By using the "edge" property of sysfs GPIOs, you can use poll(),
> select() or epoll() to efficiently wait for GPIO input events.
>
> The Overo has lots of pins that you can use as GPIOs. The thing is, lots
> of them are assigned to other functions by default. But, you can change
> that by adjusting the pin multiplexing ("pin mux") in the kernel and/or
> U-boot to use them.
>
> Also, if you share more details about your application it would people
> here to provide useful info.
>
> Best wishes
> Markus
>
>
> On 03/18/2014 02:53 PM, Roque Lora wrote:
> >
> > Good afternoon,
> >
> > I want to set up a pin of an overo fire as a timer in capture mode but
> > I do not know where to look for this information. I have read a lot of
> > articles and datasheets but it does not work for the distribution that
> > I am using, Linaro (Yocto Project).
> >
> > Could you help me with this?
> >
> > Best regards
> > --
> > Roque Lora
> > Graduate Research Assistant of Electrical Engineering
> > AggieAir Flying Circus (http://aggieair.usu.edu/)
> > Utah State University
> > Logan, UT, USA
> >
> >
> > ------------------------------------------------------------------------------
> > Learn Graph Databases - Download FREE O'Reilly Book
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> > applications. Written by three acclaimed leaders in the field,
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> >http://p.sf.net/sfu/13534_NeoTech
> >
> >
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>
>
> 2014-03-18 12:44 GMT-06:00 Roque Lora <roq...@gm... 
> <mailto:roq...@gm...>>:
>
>     Good afternoon,
>
>     I want to set up a pin of an overo fire as a timer in capture mode
>     but I do not know where to look for this information. I have read
>     a lot of articles and datasheets but it does not work for the
>     distribution that I am using, Linaro (Yocto Project).
>
>     Could you help me with this?
>
>     Best regards
>
>     -- 
>     Roque Lora
>     Graduate Research Assistant of Electrical Engineering
>     AggieAir Flying Circus (http://aggieair.usu.edu/)
>     Utah State University
>     Logan, UT, USA
>
>
>
>
> -- 
> Roque Lora
> Graduate Research Assistant of Electrical Engineering
> AggieAir Flying Circus (http://aggieair.usu.edu/)
> Utah State University
> Logan, UT, USA
>
>
> ------------------------------------------------------------------------------
> Learn Graph Databases - Download FREE O'Reilly Book
> "Graph Databases" is the definitive new guide to graph databases and their
> applications. Written by three acclaimed leaders in the field,
> this first edition is now available. Download your free book today!
> http://p.sf.net/sfu/13534_NeoTech
>
>
> _______________________________________________
> gumstix-users mailing list
> gum...@li...
> https://lists.sourceforge.net/lists/listinfo/gumstix-users