Out of tree LVGL driver

[Toby Jaffey]

I am attempting to interface an nRF54L15 to an NV3007 LCD display and make use of LVGL.
From what I can see, there is an nv3007 driver in LVGL, but not in the version of LVGL bundled with any of the Zephyr nRF SDKs
github.com/.../lv_nv3007.c

I am attempting to build the above driver by adding it to my app code. However, it fails to link.

/src/lv_nv3007.c:186: undefined reference to `lv_lcd_generic_mipi_create'
/opt/nordic/ncs/toolchains/5c0d382932/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd: lv_nv3007.c:193: undefined reference to `lv_lcd_generic_mipi_send_cmd_list'

1. Is it possible to build this driver out of tree as part of my app code, or is lvgl.a perhaps not exporting these symbols?
2. Is it possible to use the latest lvgl with Zephyr on nRF54L15?
3. Is there some other way to resolve this?

Thanks

[Øyvind]

Hello, 

I am attempting to interface an nRF54L15 to an NV3007 LCD display and make use of LVGL.

What version of the nRF Connect SDK are you running? This will determine what version of LVGL is bundled. There does not seem to be any drivers for the NV3007 LCD display in the Zephyr repository. You might have to add these yourself, have a look at Lesson 7 in the Developer Academy course nRF Connect SDK Intermediate

1. Is it possible to build this driver out of tree as part of my app code, or is lvgl.a perhaps not exporting these symbols?
2. Is it possible to use the latest lvgl with Zephyr on nRF54L15?
3. Is there some other way to resolve this?

I would yes to all of the above,  you just need to get the correct drivers for the device. There are several displays supported in the Zephyr OS i.e. The Display subsystem in Zephyr provides a unified way to interact with a wide range of display devices. You might have to reach out to the Zephyr community on Discord, where I see there is a question about the NV3007 display (without answers).

What happens if you just copy the driver files from that Git hash into modules\lib\gui\lvgl\src\drivers\display? https://github.com/lvgl/lvgl/commit/ae32d5ae6c91c680be87d51055551a1b8ba12250

Kind regards,
Øyvind

[Toby Jaffey]

Thank you for the advice. It turned out that I was taking the wrong approach.
Rather than build lvgl's own nv3007 driver, I needed to write a new Zephyr nv3007 display driver on mipi-dbi-spi. Zephyr's LVGL then runs cleanly on top of this.

Initially, I developed the driver inside of ncs (`/opt/nordic/ncs/v3.1.1`) as it allowed cloning and modifying existing drivers.
However, when I brought the driver into my own project to be build "out of tree" it would always fail to link the devicetree node.

The solution is here: devzone.nordicsemi.com/.../out-of-tree-driver---zephyr-freestanding-app specifically, replacing:

`add_subdirectory(drivers)` with `list(APPEND ZEPHYR_EXTRA_MODULES ${CMAKE_CURRENT_SOURCE_DIR}/drivers)`

[Øyvind]

Hello, I'm glad you were able to solve the issue. Are you able to run the display as intended with LVGL?

[Toby Jaffey]

Yes, lvgl_init() handles picking up the chosen display and works correctly.

[Øyvind]

That's great!