On Wednesday 30 June 2010 08:06:38 pm Nicolas Luna wrote:
> Hi,
>
> With the code below in da850-board-evm.c, I can turn on my LED connected to
> the gpio.
>
> #define DA850_LED0_GPIO GPIO_TO_PIN(8, 14)
>
> status = gpio_request(DA850_LED0_GPIO, "led0gpio");
> if (status < 0) {
> return status;
> }
> gpio_direction_output(DA850_LED0_GPIO, 0);
> gpio_set_value(DA850_LED0_GPIO, 0);
>
> If I comment this code in the kernel initialization and I try what you
> proposed, I do not get the same result. (142 comes from 16*8+14)
>
> # echo 142 > /sys/class/gpio/export
>
> # ls /sys/class/gpio
> export gpio142 gpiochip128 gpiochip64 unexport gpiochip0 gpiochip32
> gpiochip96
>
> # cat /sys/class/gpio/gpio142/value
> 1
>
> # echo 1 > /sys/class/gpio/gpio142/direction
> # echo 0 > /sys/class/gpio/gpio142/value
> # cat /sys/class/gpio/gpio142/value
> 1
>
> The output is always to 1, in fact the gpio is not in output, it is still
> in tri-state. CONFIG_GPIO_SYSFS is enabled.
>
> Do you have any idea?
>
Maybe you have a pinmux specific configuration in your board file as well?
Regards,
Caglar
> Thanks.
>
> Regards,
>
> Nicolas
>
>
>
> On Wed, Jun 30, 2010 at 3:28 AM, Christophe Aeschlimann <
>
> [email protected]> wrote:
> > Hi,
> >
> > On 30.06.2010 04:09, Jon Povey wrote:
> >> Nicolas Luna wrote:
> >>> Hi,
> >>>
> >>> I wonder what would be the easiest way to control GPIO in userspace.
> >>> I read the documentation gpio.txt but I'm not sure what I should use
> >>> (Control interfaces?, GPIO controllers?) and how to implement it.
> >>>
> >>> Is there more explication about int gpio_export_link(struct device
> >>> *dev, const char *name, unsigned gpio) because I think it could be
> >>> the key.
> >>>
> >>> Will I need to write my own module and communicate with it?.
> >>
> >> You don't need to write a module. You can access GPIOs from a shell
> >> script:
> >
> > To be able to do so you must configure your kernel with the following
> > option enabled :
> >
> > CONFIG_GPIO_SYSFS
> >
> >
> > echo $GPIO_NUMBER> /sys/class/gpio/export
> >
> >> creates a directory /sys/class/gpio/gpio$GPIO_NUMBER, e.g. 8.
> >> (That will fail if something else like a driver has requested that gpio
> >> already).
> >>
> >> cat /sys/class/gpio/gpio8/value
> >>
> >> gets the value 0/1
> >>
> >> echo 1> /sys/class/gpio/gpio8/direction
> >>
> >> sets it to output (iirc)
> >>
> >> echo 1> /sys/class/gpio/gpio8/value
> >>
> >> now sets the output value.
> >>
> >> echo 8> /sys/class/gpio/unexport
> >>
> >> to release it when you are finished.
> >>
> >> gpio_export_link() is for when you claim a gpio for use in the kernel
> >> but also want to export one of the above kind of sysfs entries.
> >>
> >> --
> >> Jon Povey
> >> [email protected]
> >>
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> >> 2743719 .
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> > Regards,
> >
> >
> > --
> > Christophe Aeschlimann
> >
> > Embedded Software Engineer
> >
> > Advanced Communications Networks S.A.
> >
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> >
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