SSD1306+lvgl sample fails to display

[zpm1066]

Describe the bug
I'm able to build the sample "zephyrproject/zephyr/samples/subsys/display/lvgl" for a nrf52840 board using an overlay. The program builds fine but a connected generic OLED SSD1306 128x64 display (also a ssd1306 Adafruit FeatherWing OLED - 128x64) fails to display anything.
The sample code hasn't been modified.

Please also mention any information which could help others to understand
the problem you're facing:

• What target platform are you using?
  nrf52840 board (particle_xenon)

• What have you tried to diagnose or workaround this issue?
  In debug, it appears that the program crashes within lv_task_handler().

• Is this a regression?
  Unable to determine, as I cannot get the SSD1306 + lvgl to work with several Zephyr versions.

To Reproduce
Steps to reproduce the behavior:

1. Use the sample code "zephyrproject/zephyr/samples/subsys/display/lvgl" as is.
2. Use the proj.conf and particle_xenon.overlay below.

particle_xenon.overlay:

/ {
	chosen {
		zephyr,display = &ssd1306;
	};
};


&pinctrl {
		i2c0_default: i2c0_default {
			group1 {
				psels = <NRF_PSEL(TWIM_SDA, 0, 26)>,
					<NRF_PSEL(TWIM_SCL, 0, 27)>;
			};
		};
	
		i2c0_sleep: i2c0_sleep {
			group1 {
				psels = <NRF_PSEL(TWIM_SDA, 0, 26)>,
					<NRF_PSEL(TWIM_SCL, 0, 27)>;
				low-power-enable;
			};
		};
};

&gpio0{
	status = "okay";
};


&gpio1{
	status = "okay";
};

&i2c0 {
	compatible = "nordic,nrf-twim";
	status = "okay";
	pinctrl-0 = <&i2c0_default>;
	pinctrl-1 = <&i2c0_sleep>;
    pinctrl-names = "default", "sleep";

	status = "okay";
	ssd1306: ssd1306@3c {
		compatible = "solomon,ssd1306fb";
		reg = <0x3c>;
		width = <128>;
		height = <64>;
		segment-offset = <0>;
		page-offset = <0>;
		display-offset = <0>;
		multiplex-ratio = <63>;
		segment-remap;
		com-invdir;
		prechargep = <0x22>;
	};
};

proj.conf:

CONFIG_MAIN_STACK_SIZE=2048

CONFIG_I2C=y
CONFIG_I2C_NRFX=y
CONFIG_LOG=y

CONFIG_DISPLAY=y
CONFIG_DISPLAY_LOG_LEVEL_ERR=y

CONFIG_SSD1306=y
CONFIG_SSD1306_DEFAULT=y

CONFIG_LVGL=y
CONFIG_LV_MEM_CUSTOM=y
CONFIG_LV_USE_LOG=y
CONFIG_LV_USE_LABEL=y
CONFIG_LV_USE_BTN=y
CONFIG_LV_USE_IMG=y
CONFIG_LV_FONT_MONTSERRAT_14=y

CONFIG_LV_Z_BITS_PER_PIXEL=1
CONFIG_LV_Z_MEM_POOL_NUMBER_BLOCKS=8
CONFIG_APP_LINK_WITH_LVGL=y

Expected behavior*
I expected the lvgl sample to work with the ssd1306 display and show the "Hello world!" text in the middle of the display.

Impact
Unable to use SSD1306 + lvgl on several key projects.

Logs and console output
Program builds without any errors.

Environment (please complete the following information):
macOS Big Sur & Catalina
Zephyr RTOS v3.1 and 3.2

Additional context
The same SSD1306 display with exactly the same overlay & connections works fine with nrf52840 and other boards when using SSD1306 with cfb_custom_font & cfb samples.

[zpm1066]

@laurenmurphyx64, @henrikbrixandersen, @jfischer-no, @brgl
I'm also going to create an account at lvgl.com to see if they can also investigate, as I don't see anything wrong with the Zephyr code.

I have several types of displays (ST7789v, ili9341 - 1.14" to 2.8") that all work just fine with Zephyr + lvgl. SSD1306 works fine with Zephyr on it's own. There may be a SSD1306 binding issue with lvgl.

I'll be glad to assist with further debugging of SSD1306/lvgl. Thanks.

[jfischer-no]

Zephyr RTOS v3.1 and 3.2

I cannot confirm, works fine for me using west build -b nrf52840dk_nrf52840 samples/subsys/display/lvgl/ -- -DSHIELD=ssd1306_128x64. Moving to discussion since it is likely configuration issue.

[zpm1066]

Hi @jfischer-no, Thank you. The “ -DSHIELD=ssd1306_128x64” works!

However, I typically use a board overlay and cannot quite understand why using &i2c0 for ssd1306 in the above overlay doesn’t work. I have no problems with using the board overlays for the st7789/ili9341 displays instead of the SHIELD overlays.

Do you know why the overlay doesn’t work? It seems I’m missing some configuration.

Can you please try using a nrf52840dk_nrf52840.overlay with the ssd1306 device definition instead of the ssd1306_128x64 shield? Thank you.

[jfischer-no]

Can you please try using a nrf52840dk_nrf52840.overlay with the ssd1306 device definition instead of the ssd1306_128x64 shield? Thank you.

It is unlikely that I will find the time, sorry.

[zpm1066]

Hi @jfischer-no , not a problem.

Do you see anything wrong with the overlay and proj.conf I have defined for particle_xenon?

Any suggestion as to what I should check next? Thanks.

[henrikbrixandersen]

I suggest checking the differences between the generated zephyr.dts file when using the shield vs. using your overlay.

[zpm1066]

@jfischer-no , @henrikbrixandersen - I've fixed the lvgl configuration issues and now are able to use the board overlay instead of the ssd1306_128x64 SHIELD overlay.

The fixed turned out be pretty simple. Earlier, I neglected to check the Kconfig.defconfig for the ssd1306_128x64 SHIELD.

My proj.conf was missing entries to set color depth for ssd1306 to monochrome (ssd1306 default was 16). In addition, LV_Z_VDB_SIZE setting was missing, causing a crash in the lv_task_handler().

CONFIG_LV_USE_THEME_DEFAULT=y
CONFIG_LV_Z_VDB_SIZE=64
CONFIG_LV_COLOR_DEPTH_1=y

I also used the LV_USE_THEME_DEFAULT, so that in the code I could flip the display primary & secondary colours.

lv_disp_t * lv_disp = lv_disp_get_default();
lv_theme_default_init(lv_disp, lv_color_black(), lv_color_white(), 1, &lv_font_montserrat_14);

For the nRF52, nRF53, microbit v2, and nrf9160, I use the excellent nRF Connect for VSCode. Using the Kconfig GUI, I was able to note immediately the issues.

The built in SHIELD overlays are quite useful as well but generally I prefer to use the board overlays.

Thank you for your assistance.