Reading the output pin value

[nikitag]

Hi!

We use the following approach:

• If the pin is configured using nrf_gpio_cfg_input we read the pin value via nrf_gpio_pin_read;
• If the pin is configured using nrf_gpio_cfg_output we read the pin value via nrf_gpio_pin_out_read;

We use nrf_gpio_pin_write to write the pin value (as I see it uses nrf_gpio_pin_set to write the value).

But after writing via nrf_gpio_pin_write we see the different value when reading via nrf_gpio_pin_out_read. As I see nrf_gpio_pin_set sets the value of OUTSET using nrf_gpio_port_out_set. And nrf_gpio_pin_out_read reads the value of OUT. 

My question is what is the difference between nrf_gpio_port_out_set and nrf_gpio_port_out_write? When can we use nrf_gpio_pin_out_read to read the last written value?

[Kenneth]

You can read the difference between OUT and OUTSET here:
https://infocenter.nordicsemi.com/topic/ps_nrf52840/gpio.html#register.OUT 

For instance notice the "Write: a '1' sets the pin high; a '0' has no effect" for OUTSET.

Kenneth

[nikitag]

As I understand, nrf_gpio_pin_out_read can be used only if nrf_gpio_port_out_write is used. Am I right?

[Kenneth]

I am not entirely sure what you want to do here, since you are basically reading back the register you just set, but yes.

Kenneth

[nikitag]

Yes. I want to read the value of OUTPUT GPIO pin that I have written. But I have found that nrf_gpio_pin_out_read gives me back incorrect value. I am trying to figure out whether my flow is correct, because we use nrf_gpio_pin_write -> nrf_gpio_pin_set -> nrf_gpio_port_out_set to set the value of the pin and nrf_gpio_pin_out_read to read the state of the output pin. Is it correct? Can we use nrf_gpio_pin_out_read in this case?

[Kenneth]

nikitag said:

Can we use nrf_gpio_pin_out_read in this case?

Sure, but make sure to look at the implementaton of each of the calls you are making and read the GPIO chapter I linked so you can understand what each of them do, ref:
https://github.com/NordicSemiconductor/nrfx/blob/v1.9.0/hal/nrf_gpio.h 
https://infocenter.nordicsemi.com/topic/ps_nrf52840/gpio.html#register.OUT 

Kenneth