ble, lvgl, the prj.conf and RAM' overflowed by 3068 bytes error

[lcj]

I got a "Hello World" up and running with lvgl and modified the prj.conf to get the font I wanted. I folded in ble and now I am getting region `RAM' overflowed by 3068 bytes error when building. The board is a PineTime DK (nRF52932).

I am new at this and need to learn about the all the components and how they contribute to RAM, but these are only two components.

I can't tell what is driving the RAM usage, but I do see a lot of logging from lvgl like:

[373/427] Building C object modules/lvgl/CMakeFiles/..__modules__lib__gui__lvgl__zephyr.dir/opt/nordic/ncs/v2.3.0/modules/lib/gui/lvgl/src/extra/widgets/tabview/lv_tabview.c.obj

which I am not using.

It seems like the prj.conf is key to what gets included. Here is mine:

# nothing here
CONFIG_LV_Z_MEM_POOL_NUMBER_BLOCKS=8
CONFIG_MAIN_STACK_SIZE=2048
#CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048


# Display
CONFIG_SPI=y
CONFIG_DISPLAY=y
CONFIG_ST7789V=y
CONFIG_ST7789V_RGB565=y
CONFIG_DISPLAY_LOG_LEVEL_ERR=y

CONFIG_LV_CONF_MINIMAL=y
CONFIG_LOG=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_24=y
CONFIG_LV_FONT_DEFAULT_MONTSERRAT_24=y
#CONFIG_LVGL_DISPLAY_DEV_NAME="DISPLAY"

#CONFIG_ST7789V=y
CONFIG_USE_SEGGER_RTT=y

# Ble
CONFIG_BT=y
CONFIG_BT_DEBUG_LOG=y
CONFIG_BT_SMP=y
CONFIG_BT_SIGNING=y
CONFIG_BT_PERIPHERAL=y
CONFIG_BT_DIS=y
CONFIG_BT_ATT_PREPARE_COUNT=5
CONFIG_BT_BAS=y
#CONFIG_BT_HRS=y
#CONFIG_BT_IAS=y
CONFIG_BT_PRIVACY=y
CONFIG_BT_DEVICE_NAME="Test BLE Service"
CONFIG_BT_DEVICE_APPEARANCE=833
CONFIG_BT_DEVICE_NAME_DYNAMIC=y
CONFIG_BT_DEVICE_NAME_MAX=65

CONFIG_BT_KEYS_OVERWRITE_OLDEST=y
CONFIG_BT_SETTINGS=y
CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_FLASH_MAP=y
CONFIG_NVS=y
CONFIG_SETTINGS=y

There doesn't seem to be much documentation about lvgl on Zephyr for lvgl 8.3:
Zephyr — LVGL documentation

I added this to the prj.conf:

CONFIG_LV_USE_CALENDAR=n

And still see this in the terminal when building:

[171/427] Building C object modules/lvgl/CMakeFiles/..__modules__lib__gui__lvgl__zephyr.dir/opt/nordic/ncs/v2.3.0/modules/lib/gui/lvgl/src/extra/widgets/calendar/lv_calendar.c.obj

[ovrebekk]

Hi Leo

A very good tool to analyze RAM and ROM consumption in a Zephyr application is the Memory Report feature in the nRF Connect VSCode extension. 

This provides a detailed overview of exactly which variables and modules are consuming how much memory, including a graphical representation of the various modules and how much they use:

In the example above I built the LVGL basic sample for the Adafruit 2.8" TFT display on the nRF52840DK. 

The total RAM consumption is 178016 bytes, and from the memory report I can see clearly that most of this is caused by the LVGL display buffer (buf0) and the LVGL heap (lvgl_heap_mem). 

The size of the LVGL heap can be reduced by reducing CONFIG_LV_Z_MEM_POOL_NUMBER_BLOCKS, which is set to 8 in the sample. 

The size of the buffer can be reduced by reducing CONFIG_LV_Z_VDB_SIZE, which is a percentage value between 1 and 100 scaling the image buffer to the size of the screen. 

I assume smaller values will lead to higher CPU usage and slower screen updates, but will reduce RAM consumption. 

Best regards
Torbjørn 

[lcj]

I did reduce CONFIG_LV_Z_MEM_POOL_NUMBER_BLOCKS to 6 and it did build. That's a great report. Lvgl is 56%:

Does it look like there are lvgl modules I should not have in there?

This forum is great! Thank you so much for this.

[ovrebekk]

Hi 

Great to hear you got it to build

You might want to reduce the other parameter as well to give you a bit more overhead, depending on your application I am guessing you might need more RAM later when adding new features. 

The memory report is indeed very useful. Especially the fact that you can click on elements in the report and jump directly to the implementation in the code, this allowed me to investigate which configuration parameters had to be changed to reduce the buffers. 

There is also a search function if you want to search for specific modules (such as the calendar one). 

lcj said:

Does it look like there are lvgl modules I should not have in there?

Based on the screenshot I can't really see any superfluous modules, no. I wouldn't worry too much about unused modules, the linker should optimize them out if they are not referenced anywhere. 

Best regards
Torbjørn

[lcj]

Thank you! Looks like lvgl 8 is a lot bigger than 7. Some others working on the PineTime have stayed with 7 for this reason.

[ovrebekk]

Hi Leo

It makes sense that the older versions would be leaner, if you don't need the features of v8. 

A shame the PineTime doesn't use the nRF52840 though, then you would have much more memory available... (I am sure they had their reasons to use the nRF52832 instead)

Best regards
Torbjørn