lvgl on nrf54l15

[Michal]

Hi,

I am trying to use lvgl on nrf54l15, but I am facing issues with spi. I was trying first to use vanilla zephyr 4.1, but now I switched to ncs 3.1.1. I am trying to run samples/subsys/display/lvgl . I first launched it on nrf52840 and that worked fine - attached is overlay file 4848.nrf52840dk_nrf52840.overlay. Then I tried to do the same on nrf54l15 but wasn't able to0638.nrf54l15dk_nrf54l15_cpuapp.overlay. When trying in vanilla zephyr I was obersving no clock line (I was carefully selecting pin clock pin knowing the limitations). Right now under ncs 3.1.1 it doesn't seem to work at all.

Is there something clearly long in my nrf54 overlay?

Thank you,
Michal

[Edvin]

Hello,

If you look at the back of the nRF54l15DK, you can see that the P1.03 is one of the NFC pins. If you want to use the NFC pins as normal GPIOs (like in this case, for SPI), you need to modify the DK a bit:

https://docs.nordicsemi.com/bundle/ug_nrf54l15_dk/page/UG/nRF54L15_DK/hw_desription/nfc_if.html#d18e103

I think, without modifying anything on the HW side , it is probably easier to test another set of pins. You can use these pins on SPIM21:

P2.06 SCK

P2.10 CS 

P2.08 MOSI

P2.09 MISO

According to:

https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/chapters/pin.html

See if that works, and let me know if it doesn't.

You can also use the pins that you picked earlier, but it requires you to desolder and re-solder some 0R resistors on the DK, according to the description in my first link, in addition to adding this snippet to your nrf54l15dk_nrf54l15_cpuapp.overlay:

&uicr {
    nfct-pins-as-gpios;
};

Best regards,

Edvin

[Michal]

Hi,

Thanks, that seems to have helped for the clock issue ! I have tried the same pin mapping but using SPI00 and it wasn't working, any idea why that could be? Could it be because of the external flash that is by default connected to SPI00?

However right now I have an issue with dc pin - I don't see any change in the signal state while I see it for nrf52840 setup. Any idea there? I tried to change to other pin - 2.14 - but that didn't solve the problem.

Best regards,
Michal

[Edvin]

Michal said:

Thanks, that seems to have helped for the clock issue ! I have tried the same pin mapping but using SPI00 and it wasn't working, any idea why that could be? Could it be because of the external flash that is by default connected to SPI00?

might be. Try using SPIM21. The pins should not be in use, as they use P2.00-P2.05. The external flash does however use SPI00 by default, so alternatively, you can try to disable that in the overlay file. You need to delete the mx25r64 node:

/delete-node/ &mx25r64;

to make it not try to take over your spi00.

Regarding your DC pin, I am not sure how it should usually be controlled. Does it work in the project for nRF52840?

Best regards,

Edvin

[Michal]

Hi Edvin,

So I changed DC pin and it is changing state now. However, project on nrf52840 properly initialize the display and displays basic data, while on nrf54l15 it doesn't work, even though on the logic analyzer everything seems fine.

Yes, samples/subsys/display/lvgl example works on my nrf52840 + st7789, but no on nrf54.

Best regards,
Michal

[Edvin]

The logic trace must differ at one place, or else the display would behave the same. Do you see any difference? Particularly near the start of the application?

And one thing, is the nRF54L15 running at 3.3V or 1.8V? If it is not running at 3.3V, please use nRF Connect for Desktop -> Board configurator to increase the P2 voltage from 1.8V to 3.3V. Perhaps the display doesn't work at 1.8V, and this is what you are using.

Best regards,

Edvin

[Michal]

Hi Edvin,

Yes, this was definietly part of the problem, I can finally see something on the screen ! Data displayed is still malformed, so I will keep investigating.

Thanks !