Error in Settings API on saving BLE connection properties

[Evgeny M]

Hello,

I'm implementing a device based on the NRF52840 Dongle and the hids keyboard example. The basic functionality work, so that I can send pressed keys to a connected device. The problem is that after the restart/power loss, the devices must be paired again.

I added SETTINGS related variables to the prj.conf:

CONFIG_SETTINGS=y
CONFIG_SETTINGS_RUNTIME=y

# NVS variables when enabled prevent boot. Even serial port is not visible in the system
# CONFIG_NVS=y
# CONFIG_SETTINGS_NVS=y

# Setting these two does not change the behavior.
# CONFIG_FCB=y
# CONFIG_SETTINGS_FCB=y

# This variable gets "y" in the build unless NVS or FCB is enabled
# CONFIG_SETTINGS_NONE=n

CONFIG_BT_SETTINGS=y
CONFIG_BT_GATT_CACHING=n
CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_FLASH_MAP=y

main.c:

int main(void)
{
	if (IS_ENABLED(CONFIG_SETTINGS)) {
		err = settings_load();
		if (!err) {
			printk("settings_load done\n");
		} else {
			printk("settings_load failed, err=%d\n", err);
		}
	}
	
	err = bt_enable(NULL);
	if (err) {
		printk("Bluetooth init failed (err %d)\n", err);
		return 0;
	}
	printk("Bluetooth initialized\n");

	if (IS_ENABLED(CONFIG_SETTINGS)) {
		// see bt_enable() description
		err = settings_load_subtree("bt");
		if (!err) {
			printk("settings_load BT done\n");
		} else {
			printk("settings_load BT failed, err=%d\n", err);
		}
	}
	
	...

After the successful connection I see several error messages in the console:

Connected 64:6E:E0:48:6A:A1 (public)
E: Failed to save keys (err -2)
Pairing completed: 64:6E:E0:48:6A:A1 (public), bonded: 1
HID service notified
E: Failed to store CCCs (err -2)
Security changed: 64:6E:E0:48:6A:A1 (public) level 2
E: failed to store SC (err -2)
Output report read
E: Failed to store CCCs (err -2)

E: Failed to store CCCs (err -2)

I tried already different CONFIG combinations, nothing worked. What I'm doing wrong?

Thank you for your answers.

468744.prj.conf

[Amanda Hsieh]

Hi, 

See this Nordic Academy course https://academy.nordicsemi.com/courses/bluetooth-low-energy-fundamentals/lessons/lesson-5-bluetooth-le-security-fundamentals/topic/blefund-lesson-5-exercise-2/ 

Regards,
Amanda H.

[Evgeny M]

Hello Amanda, thank you the the response.

I have actually done this course a year or two ago.

Unfortunately I don't have NRF52840DK, but back then everything worked also with a dongle.

Now I'm using the latest SDK 2.9.0 and the last version of NRF Connect for VSCode, probably something changed?

I also tried this example form Zephyr repository https://docs.zephyrproject.org/latest/samples/drivers/soc_flash_nrf/README.html.

The result is the same - after any write/erase command there is a fault and the MCU stops working.

[Amanda Hsieh]

Could you try the NCS v2.9.0 solution https://github.com/NordicDeveloperAcademy/bt-fund/tree/main/v2.9.0-v2.7.0/l5/l5_e2_sol, which also provides the board setting for nrf52840dongle?  

[Evgeny M]

I tried, I made a fresh installation of sdk and the toolchain.

The result is the same. I don't see the USB port after the application start.

I tried to debug, but ran into another problem, GDB server kills the app after the initial break point. Somehow auto confirmation is configured or may be it is so be default.

This is the output:

Thread 2 received signal SIGTRAP, Trace/breakpoint trap.
0x00000578 in ?? ()
Kill the program being debugged? (y or n) [answered Y; input not from terminal]
[Inferior 1 (Remote target) killed]

This part is strange "answered Y; input not from terminal".

There is a command in GDB `set confirm off` but I don't know how to apply it in NRF Connect fro VSCode

[Amanda Hsieh]

Evgeny M said:

The result is the same. I don't see the USB port after the application start.

For the setup, you can refer to samples/subsys/usb/console. 

Evgeny M said:

I tried to debug, but ran into another problem, GDB server kills the app after the initial break point. Somehow auto confirmation is configured or may be it is so be default.

The nRF52840 Dongle is provided as the propopyping and doesn't have an onboard debugger, so it is unsuitable for development. Please use nRF52840DK to debug.