How to define a direct GPIO IRQ in zephyr

[Kimcha]

Hi,

I am developing a PS/2 bitbanging driver for zephyr. The PS/2 device (a mouse in my use case) is connected to the mcu using two GPIO pins  

I got it working using the zephyr GPIO API interrupts, but frequently the interrupts are missed or not delivered on time. 

I would like to try using direct interrupts, but cannot figure out how to configure them.

An additional difficulty is that the target application for this driver also uses interrupts for many other pins, also using the zephyr GPIO API.

I think that under the hood zephyr is using the port event to detect changes on the pins.

But apparently, it’s also possible to configure an interrupt using one of the 8 (or 16?) gpiote channels.

But I can’t find documentation to figure what the parameters for IRQ_DIRECT_CONNECT should be for a specific pin  

Can someone link me to some sample code or documentation perhaps?

To clarify, my question is: Is it possible to set up a two direct interrupt for two pins even though zephyr is already using the zephyr GPIO API for interrupts on other pins.

If it’s possible, then how?

If it’s not possible due to how zephyr implemented their GPIO functionality, how could I modify it to add my own direct interrupts?

Thank you so much for your help in advance  

when the PS/2 mouse 

[Hieu]

Hi Kimcha,

But I can’t find documentation to figure what the parameters for IRQ_DIRECT_CONNECT should be for a specific pin  

Can someone link me to some sample code or documentation perhaps?

You cannot use IRQ_DIRECT_CONNECT because the Zephyr GPIO API already connected a different interrupt handler to the GPIOTE IRQ.

To clarify, my question is: Is it possible to set up a two direct interrupt for two pins even though zephyr is already using the zephyr GPIO API for interrupts on other pins.

If it’s possible, then how?

Yes~ish. You might theoretically be able to use the nrfx GPIOTE driver API together with the Zephyr GPIO API.

I don't recommend this very much. A driver can be stateful. As far as I can see, the nrfx driver is stateful, but only for the purpose of GPIOTE channel use tracking. Since the Zephyr GPIO API is actually implemented with nrfx GPIOTE driver API under the hood, they can work together. 

Having said all that, please still be very careful about doing it. Please take some time to analyze the Zephyr GPIO API implementation and understand its use of the nrfx driver.

The nrfx GPIOTE driver is documented here: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.4.2/nrfx/drivers/gpiote/index.html.

There is a sample of nrfx GPIOTE driver usage here: sdk-zephyr/samples/boards/nrf/nrfx at v3.3.99-ncs1 · nrfconnect/sdk-zephyr (github.com).
One thing to notice is that in the sample, the IRQ handler has to be connected in the application. However, as stated earlier above, when you also use the Zephyr GPIO API, the IRQ handler is already connected.

You will also find the HAL API. I recommend against using it at the same time as either of the drivers above. That is because the HAL API interacts with the hardware directly and without regard of the state of the nrfx driver.

Hieu

P.s: Please also note that the above information is applicable only for the GPIO/GPIOTE peripheral. It is likely different for other peripherals, depends on how the APIs are implemented.