[#5627] fail to control gpio used by led and button through /sys/class/gpio/

Submitted By: Mingquan Pan

Open Date

2009-10-19 06:16:18 Close Date

2009-10-20 05:49:57

Priority:

Medium Assignee:

Michael Hennerich

Status:

Closed Fixed In Release:

N/A

Found In Release:

2010R1 Release:

Category:

N/A Board:

N/A

Processor:

BF537 Silicon Revision:

Is this bug repeatable?:

Yes Resolution:

Not reproducible

Uboot version or rev.:

Toolchain version or rev.:

09r1-rc9

App binary format:

N/A

Summary: fail to control gpio used by led and button through /sys/class/gpio/

Details:

After enabling in the kernel:

CONFIG_ARCH_WANT_OPTIONAL_GPIOLIB=y

CONFIG_GPIOLIB=y

# CONFIG_DEBUG_GPIO is not set

CONFIG_GPIO_SYSFS=y

I try to use /sys/class/gpio/ to control led and button on bf537 stamp.

based on the table:

" BF537-STAMP:\n"

"\tLED1 => GPIO6\tPB1 => GPIO2\n"

"\tLED2 => GPIO7\tPB2 => GPIO3\n"

"\tLED3 => GPIO8\tPB3 => GPIO4\n"

"\tLED4 => GPIO9\tPB4 => GPIO5\n"

"\tLED5 => GPIO10\n"

"\tLED6 => GPIO11\n"

I export gpio2 and 6, and changed the LED1 direction to out and set its value from 0 to 1, but the led is always on and nothing happened. As to the button, whatever I push the button, the value is also not changed.

root:/> cd /sys/class/gpio/

root:/> echo 2 > export

root:/> echo 6 > export

root:/sys/class/gpio> ls

export gpio2 gpio6 gpiochip0 unexport

...

root:/sys/class/gpio> cat gpio2/direction

root:/sys/class/gpio> cat gpio2/value

root:/sys/class/gpio> cat gpio6/direction

out

root:/sys/class/gpio> cat gpio6/value

So is there anything else I need to do to manipulate the gpio sys interface?

Follow-ups

--- Michael Hennerich 2009-10-19 06:49:45

http://docs.blackfin.uclinux.org/doku.php?id=linux-kernel:drivers:gpio-sysfs&s[]=gpiolib

PF6 aka GPIO_6 = LED1:

root:/sys/devices/virtual/gpio/gpio4> cd /sys/class/gpio/

root:/sys/class/gpio> echo 6 > export

root:/sys/class/gpio> echo low > gpio6/direction

root:/sys/class/gpio> echo high > gpio6/direction

root:/sys/class/gpio> echo low > gpio6/direction

root:/sys/class/gpio>

Works

PF8 aka GPIO_8 = LED3:

root:/sys/class/gpio> echo 8 > export

root:/sys/class/gpio> cd gpio8/

root:/sys/devices/virtual/gpio/gpio8> ls

direction power subsystem uevent value

root:/sys/devices/virtual/gpio/gpio8> echo high > direction

root:/sys/devices/virtual/gpio/gpio8> echo low > direction

root:/sys/devices/virtual/gpio/gpio8>

Works for me…

PF4 aka GPIO_4 = PB3:

root:/sys/class/gpio> echo 4 > export

root:/sys/class/gpio> cd gpio4/

root:/sys/devices/virtual/gpio/gpio4> ls

direction power subsystem uevent value

root:/sys/devices/virtual/gpio/gpio4> echo in > direction

root:/sys/devices/virtual/gpio/gpio4> cat value

root:/sys/devices/virtual/gpio/gpio4>

Works for me, too.

Did you connect SW5?

--- Mingquan Pan 2009-10-19 23:07:48

Yeah, following your steps, it is working on my side too.

But there is still some issue for the button accepting the pushing action.

If I don't run the command : echo in > direction at the first, since the

default direction for the button is in, then cat value won't notice the pushing

action and get the changing result, remaining 0, like:

PF5 aka GPIO_5 = PB4:

root:/sys/class/gpio> echo 5 > export

root:/sys/class/gpio> cd gpio5/

root:/sys/devices/virtual/gpio/gpio5> ls

direction power subsystem uevent value

root:/sys/devices/virtual/gpio/gpio5> cat direction

root:/sys/devices/virtual/gpio/gpio5> cat value

--- Michael Hennerich 2009-10-20 04:00:53

The default direction of a GPIO which direction is not written - is not

defined.

The default DIR is 'in' - but upon reset the INEN Input Enables are

disabled - so you won't be able to read whatever happens on the pin

Level.

- Refused -

You need to write 'direction' prior in using the gpio anyhow -

-Michael

--- Mingquan Pan 2009-10-20 05:49:57

All right. So echo the value to the direction before operatating on the gpios.

Close it.

Files

Changes

Commits

Dependencies

Duplicates

Associations