i.MX ProcessorsのトピックGPIO set value and get value

GPIO set value and get value

cilymo — Fri, 04 Aug 2017 06:54:24 GMT

Hi:

I'm confused for the gpio control. Here is my step:

1: int pin_num = of_get_named_gpio(np, "345-en,fsl", 0); //GPIO2 IO03 pin_num = 35;

2: gpio_direction_output(pin_num, 1); //Voltage high

3: gpiod_get_value(gpio_to_desc(pin_num)); //get "0"

4: gpiod_set_value(gpio_to_desc(pin_num),0); //voltage low

5: gpiod_get_value(gpio_to_desc(pin_num)); //get "0"

6: gpiod_set_value(gpio_to_desc(pin_num),1); //voltage high

7: gpiod_get_value(gpio_to_desc(pin_num)); //get "0"

Every time I get the gpio value is "0", but the pin voltage is the same(high/low) what I set. how can i get the GPIO value after i set.

Re: GPIO set value and get value

Rita_Wang — Fri, 04 Aug 2017 07:46:37 GMT

Which board and which version BSP are you using?

Re: GPIO set value and get value

cilymo — Fri, 04 Aug 2017 07:49:46 GMT

Hi,

I use imx6dl, and BSP version is 4.1.15_2.0.1.

Thanks.

Re: GPIO set value and get value

Rita_Wang — Fri, 04 Aug 2017 08:29:19 GMT

The GPIO module provides general-purpose pins that can be configured as either inputs
or outputs.
When configured as an output, the pin state (high or low) can be controlled by writing to
an internal register. When configured as an input, the pin input state can be read from an
internal register.

If a pin is configured as GPIO by the IOMUX, the state of the pin should also be set since
it is not initialized by a dedicated hardware module. Setting the pad pull-up, pull-down,
slew rate and so on, with the pad control function may be required as well.
Detail you can refer to the i.MX_Linux_Reference_Manual.pdf,