Set and clear GPIO pins at the same time

RE: Set and clear GPIO pins at the same time

NewtoM — Mon, 03 Oct 2016 17:42:42 GMT

Thank you both!

RE: Set and clear GPIO pins at the same time

ovrebekk — Mon, 03 Oct 2016 08:39:54 GMT

Hi NewtoM

I can't think of any concerns when accessing GPIO->OUT, other than making sure you don't change bits in the register that you are not supposed to change. There is no way to accept multiple answers unfortunately, but RK's answer already got more upvotes so I suggest you accept that ;)

RE: Set and clear GPIO pins at the same time

NewtoM — Sat, 01 Oct 2016 20:03:42 GMT

Thanks RK, thanks Torbjørn,

now I see the idea. If I look at the nrf_gpio_pins_toggle() function, I see how the GPIO->OUT register state read. Is there anything I should be aware of when directly reading/writing the OUT register?

And can I accept both answers? :)

NewtoM

RE: Set and clear GPIO pins at the same time

ovrebekk — Fri, 30 Sep 2016 15:12:28 GMT

Hi NewtoM

If you want to do this you probably have to bypass the nrf_gpio functions, and write directly to the GPIO registers. Fortunately it isn't as scary as it sounds ;)

To set/clear many pins at once you can write to the OUTSET or OUTCLR registers in the NRF_GPIO peripheral.

If you want to set and clear many pins at once you have to use the OUT register.

Say you want to set pins P0.08-P0.011 to 0xA you could do it like this:

pin_mask = 0xF << 8;
NRF_GPIO->OUT = (NRF_GPIO->OUT & ~pin_mask) | (0xA << 8);

You can still use the nrf_gpio driver to configure the outputs, and set/clear individual pins.

-Torbjørn

RE: Set and clear GPIO pins at the same time

RK — Fri, 30 Sep 2016 12:32:23 GMT

Read the GPIO port to get the current state, set and clear bits in that value, then write it back.

Just as there is a GPIO->OUTSET and a GPIO->OUTCLR register, so there is a GPIO->OUT register you can write to set the whole register at once.