Central BLE 4.1 to Zephyr periperal with NRF52

[Alex-Lipskiy]

Hi!

I can't connect the central CC2640 (BLE version 4.1) and the peripheral Zephyr 3.0.99 (NRF52)

The peripheral must have the following mode:
IO_CAP_DISPLAY_ONLY
bonding: on
Characteristics have read and write permissions with authentication

The central working in the following mode:
IO_CAP_KEYBOARD_DISPLAY
bonding: on
A successful connection should be made after entering the correct password.

My device successfully connects and communicates with the peripheral based on CC2640 (BLE 4.1), but I cannot configure the peripheral Zephyr stack so that it can connect with central BLE 4.1. In the configuration, I disabled the security settings associated with BLE 4.2 and higher, but I still couldn’t connect this devices.

Can you give me some advice?

My peripheral device settings:
CONFIG_BT=y
CONFIG_BT_PERIPHERAL=y
CONFIG_BT_DEBUG_LOG=y
CONFIG_BT_SMP=y
CONFIG_BT_GATT_SERVICE_CHANGED=n
CONFIG_BT_GAP_PERIPHERAL_PREF_PARAMS=n
CONFIG_BT_FIXED_PASSKEY=y
CONFIG_BT_BONDING_REQUIRED=y
CONFIG_BT_SMP_APP_PAIRING_ACCEPT=y
CONFIG_BT_SMP_ENFORCE_MITM=n

In ble init:
bt_passkey_set(passkey);
bt_set_bondable(true);

In "connected" callback:
uint8_t sec_level = BT_SECURITY_L3;
if (bt_conn_set_security(conn, sec_level))

In logs:
00> Connected
00>
00> bt_conn_set_security L3 is OK
00>
00> Security failed: 18:04:ED:73:5C:AA (public) level 1 err 9
00>
00> Disconnected (reason 0x13)

I tried many combinations of security settings and BT_SECURITY_LX modes, nothing helps