User interface keys

Could you kindly tell us what is your system and what software are you using?

Hi Biser,

I am using am335x starter kit and linux platform.

Regards,

Sowmya

Hi Sowmya,

If you wish to do this from user space, you will have to use polling to see if a GPIO interrupt has arrived. This is the user-space way of doing this.

If you do it inside a kernel module, it's as easy as registering an interrupt handler and letting it do its job when a GPIO interrupt arrives. You can read more about GPIO driver usage on a kernel level here: http://processors.wiki.ti.com/index.php/GPIO_Driver_Guide

Best regards,
Miroslav

Hi Miroslav,

Can I know the path to access the interrupts.

Now for led blinking I am using :

while (1)

{

                 system ("echo 1 >/sys/class/leds/am335x:EVM_SK:usr0/brightness");

                 system ("echo 0 >/sys/class/leds/am335x:EVM_SK:usr0/brightness");

}

Like this , is there a way to read SW1/2 or any key press signal events?

Regards,

Sowmya

Sowmya, the IRQ handling for GPIOs is described in the guide above: http://processors.wiki.ti.com/index.php/GPIO_Driver_Guide#IRQ_handling

1. Map GPIO number to corresponding IRQ number:
irq_num = gpio_to_irq(30);

2. Request IRQ:
request_irq(irq_num, handler, 0, "gpio_test", NULL);
"handler" is your IRQ handler function where you would blink your LED.

3. Set IRQ type Raising/Falling/Level triggered:
set_irq_type(irq_num, IRQ_TYPE_EDGE_RISING);

4. During the clean-up path free the IRQ and gpio:
free_irq(irq_num, NULL);
gpio_free(30);

Follow these steps in the kernel module you write. If you don't know what a kernel module is or how to write one, there are plenty of guides online. For example, a good reading is the Linux Device Drivers 3rd edition.

Best regards,
Miroslav

Thank you Miroslav.

I am reading on IRQ handling and related documents. And I will go through the link above given by you.

Regards,

Sowmya

Sowmya, you can also take a look at this sample kernel module, that use a interrupt handler to print the irq number every time an interrupt is triggered. The irq number is passed as a module parameter when inserting the module. You will have to modify this and use gpio_to_irq() to get an irq number, of course.

Best regards,
Miroslav

Hi Miroslav,

I used fread to read the key event and display key pressed value and code.

Now I am able to get key event.

And the link you are giving is not opening.

Regards,

Sowmya

Sowmya BR said:

And the link you are giving is not opening.

Sorry, Just fixed the link.

Best regards,
Miroslav

Now my code is working. I am handling through event of key press.

Thank you Miroslav.

Regards,

Sowmya