Read GPIO Output State

[RPDben]

Hi,

What is the best way to read the state of an output pin? I have an LED connected to a pin and want to know in a different part of the program whether the LED is currently on or off.

Thanks,

[Nikolaus Wittenstein]

You can just check the same register that you wrote to. Are you using nrf_gpio_pin_write? If you dig into how it works, you can find the OUT, OUTSET, and OUTCLR registers. The OUTSET and OUTCLR registers simply modify the OUT register, which holds the current output state.

In conclusion, NRF_GPIO->OUT is the register you're looking for, and you just need to mask it to get the correct bit. The masking can also be found in nrf_gpio.h, and will look something like this: ((NRF_GPIO->OUT >> pin_number) & 1UL).

[Wojtek]

You may try reading OUT register of GPIO, but I don't think this is the best way to do this. It would be better to keep the state as variabl accessed by some "library", or global one.

[RPDben]

I think this is exactly what I was looking for, thanks. I will test it as soon as I can.

[Eliot Stock]

Isn't this what this function in nrf_gpio.h is doing? uint32_t nrf_gpio_pin_out_read(uint32_t pin_number)

[RPDben]

It appears so. However, this question was asked in reference to SDK 10. This function is only in SDK12 or later.