Check the bluez configuration

Oct 13, 2025 by pynkocean.com 20 views

Introduction

In this article, we will discuss a peculiar issue encountered while developing a BLE application based on Cortex-A53 processor and bluez. The application simply turns on the power and starts scanning with "transport = le" and "pattern = [First 3 bytes of MAC address]". However, after multiple hours, the scanning stops, and no devices can be scanned. We will delve into the issue, analyze the logs, and provide possible solutions.

Environment

bluez: 5.76
Linux kernel: 6.1.33
Bluetooth module: nrf52840 (Zephyr-based HCI)

Issue Description

The issue is that the scanning stops after multiple hours, and no devices can be scanned. The logs show that the scanning is started and stopped periodically by bluez, but the last "disable discovery" happens at a specific time, and no "enable discovery" is followed. This suggests that the issue is related to the bluez service.

Logs Analysis

We have analyzed the logs from btmon and DBUS. The btmon log shows that the scanning is started and stopped periodically by bluez. The last "disable discovery" happens at 2025-03-09 02:23:03.603526, and no "enable discovery" is followed. This suggests that the issue is related to the bluez service.

The DBUS log shows that the properties of the device are being changed periodically. However, there is no indication of any issues with the device or the scanning process.

Possible Solutions

Based on the analysis of the logs, we can propose the following possible solutions:

Restart the bluez service: Restarting the bluez service may resolve the issue. This can be done by running the command sudo systemctl restart bluetooth.
Check the bluez configuration: Check the bluez configuration to ensure that it is set up correctly. This can be done by running the command sudo bluez --config.
Check the Linux kernel version: Check the Linux kernel version to ensure that it is up-to-date. This can be done by running the command uname -r.
Check the Bluetooth module: Check the Bluetooth module to ensure that it is functioning correctly. This can be done by running the command sudo hciconfig.

Conclusion

In conclusion, the issue of scanning stopping after multiple hours is likely related to the bluez service. Restarting the bluez service, checking the bluez configuration, checking the Linux kernel version, and checking the Bluetooth module are possible solutions to this issue.

Recommendations

Based on the analysis of the logs and the possible solutions, we recommend the following:

Restart the bluez service: Restart the bluez service to resolve the issue.
Check the bluez configuration: Check the bluez configuration to ensure that it is set up correctly.
Check the Linux kernel version: Check the Linux kernel version to ensure that it is up-to-date.
Check the Bluetooth module: Check the Bluetooth module to ensure that it is functioning correctly.

By following these recommendations, you should be able to resolve the issue of scanning stopping after multiple hours.

Additional Information

Similar issue: There is a similar issue #343 that has been reported. Restarting the service also works in this case, but it is unacceptable for our application.
Environment: The environment is bluez 5.76, Linux kernel 6.1.33, and Bluetooth module nrf52840 (Zephyr-based HCI).

Code Snippets

Here are some code snippets that may be helpful:

btmon log: The btmon log shows the following:

...... Name (complete): EWED2B0944F750 RSSI: -62 dBm (0xc2) @ MGMT Event: Device Found (0x0012) plen 48 0x0001} [hci0] 2025-03-09 0221:02.219606 LE Address: ED:2B:09:44:F7:50 (Static) RSSI: -62 dBm (0xc2) Flags: 0x00000000 Data length: 34 Flags: 0x06 LE General Discoverable Mode BR/EDR Not Supported 16-bit Service UUIDs (complete): 1 entry Service Discovery Server Service Class (0x1000) Company: Nokia Mobile Phones (1) Data: ed2b0944f750 Name (complete): EWED2B0944F750 **@ MGMT Event: Discovering (0x0013) plen 2 {0x0001 [hci0] 2025-03-09 02:21:02.253922 Address type: 0x06 LE Public LE Random Discovery: Disabled (0x00) < HCI Command: LE Set Scan Enable (0x08|0x000c) plen 2 #955831 [hci0] 2025-03-09 02:21:02.254017 Scanning: Disabled (0x00) Filter duplicates: Disabled (0x00) > HCI Event: Command Complete (0x0e) plen 4 #955832 [hci0] 2025-03-09 02:21:02.258306 LE Set Scan Enable (0x08|0x000c) ncmd 1 Status: Success (0x00) @ MGMT Event: Command Complete (0x0001) plen 4 0x0001} [hci0] 2025-03-09 0222:34.689117 Start Service Discovery (0x003a) plen 1 Status: Success (0x00) Address type: 0x06 LE Public LE Random @ MGMT Event: Discovering (0x0013) plen 2 {0x0001 [hci0] 2025-03-09 02:22:34.689133 Address type: 0x06 LE Public LE Random Discovery: Enabled (0x01) > HCI Event: LE Meta Event (0x3e) plen 41 #955839 [hci0] 2025-03-09 02:22:34.703348** LE Advertising Report (0x02) Num reports: 1 Event type: Connectable undirected - ADV_IND (0x00) Address type: Random (0x01) Address: DE:AA:24:9A:EE:7A (Static) Data length: 29 Flags: 0x06 LE General Discoverable Mode BR/EDR Not Supported Company: North Pole Engineering (816) Data: 8301 Name (complete): LF07aee9a24aade166 RSSI: -87 dBm (0xa9) > HCI Event: LE Meta Event (0x3e) plen 41 #955840 [hci0] 2025-03-09 02:22:34.706274 LE Advertising Report (0x02) Num reports: 1 Event type: Scan response - SCAN_RSP (0x04) Address type: Random (0x01) Address: DE:AA:24:9A:EE:7A (Static) Data length: 29 16-bit Service UUIDs (partial): 1 entry Fitness Machine (0x1826) 128-bit Service UUIDs (partial): 1 entry Vendor specific ... Data length: 25 Flags: 0x06 LE General Discoverable Mode BR/EDR Not Supported Name (complete): PSR110120 Company: SKF (U.K.) Limited (1038) Data: 00000000011601 RSSI: -47 dBm (0xd1) > HCI Event: LE Meta Event (0x3e) plen 12 #957115 [hci0] 2025-03-09 02:23:03.593462 LE Advertising Report (0x02) Num reports: 1 Event type: Scan response - SCAN_RSP (0x04) Address type: Public (0x00) Address: C4:BD:6A:11:01:20 (SKF GmbH) Data length: 0 RSSI: -47 dBm (0xd1) @ MGMT Event: Device Found (0x0012) plen 39 {0x0001} [hci0] 2025-03-09 02
Q&A: Turn on Scan and Nothing Would be Scanned After Multiple Hours ====================================================================

Q: What is the issue with the BLE application?

A: The issue with the BLE application is that the scanning stops after multiple hours, and no devices can be scanned.

Q: What is the environment of the BLE application?

A: The environment of the BLE application is bluez 5.76, Linux kernel 6.1.33, and Bluetooth module nrf52840 (Zephyr-based HCI).

Q: What is the cause of the issue?

A: The cause of the issue is related to the bluez service. The scanning is started and stopped periodically by bluez, but the last "disable discovery" happens at a specific time, and no "enable discovery" is followed.

Q: How can the issue be resolved?

A: The issue can be resolved by restarting the bluez service, checking the bluez configuration, checking the Linux kernel version, and checking the Bluetooth module.

Q: What are the possible solutions to the issue?

A: The possible solutions to the issue are:

Restart the bluez service: Restarting the bluez service may resolve the issue.
Check the bluez configuration: Check the bluez configuration to ensure that it is set up correctly.
Check the Linux kernel version: Check the Linux kernel version to ensure that it is up-to-date.
Check the Bluetooth module: Check the Bluetooth module to ensure that it is functioning correctly.

Q: What are the recommendations for resolving the issue?

A: The recommendations for resolving the issue are:

Restart the bluez service: Restart the bluez service to resolve the issue.
Check the bluez configuration: Check the bluez configuration to ensure that it is set up correctly.
Check the Linux kernel version: Check the Linux kernel version to ensure that it is up-to-date.
Check the Bluetooth module: Check the Bluetooth module to ensure that it is functioning correctly.

Q: Is there a similar issue that has been reported?

A: Yes, there is a similar issue #343 that has been reported. Restarting the service also works in this case, but it is unacceptable for our application.

Q: What are the code snippets that may be helpful?

A: The code snippets that may be helpful are:

btmon log: The btmon log shows the following:

...... Name (complete): EWED2B0944F750 RSSI: -62 dBm (0xc2) @ MGMT Event: Device Found (0x0012) plen 48 0x0001} [hci0] 2025-03-09 0221:02.219606 LE Address: ED:2B:09:44:F7:50 (Static) RSSI: -62 dBm (0xc2) Flags: 0x00000000 Data length: 34 Flags: 0x06 LE General Discoverable Mode BR/EDR Not Supported 16-bit Service UUIDs (complete): 1 entry Service Discovery Server Service Class (0x1000) Company: Nokia Mobile Phones (1) Data: ed2b0944f750 Name (complete): EWED2B0944F750 **@ MGMT Event: Discovering (0x0013) plen 2 {0x0001 [hci0] 2025-03-09 02:21:02.253922 Address type: 0x06 LE Public LE Random Discovery: Disabled (0x00) < HCI Command: LE Set Scan Enable (0x08|0x000c) plen 2 #955831 [hci0] 2025-03-09 02:21:02.254017 Scanning: Disabled (0x00) Filter duplicates: Disabled (0x00) > HCI Event: Command Complete (0x0e) plen 4 #955832 [hci0] 2025-03-09 02:21:02.258306 LE Set Scan Enable (0x08|0x000c) ncmd 1 Status: Success (0x00) @ MGMT Event: Command Complete (0x0001) plen 4 0x0001} [hci0] 2025-03-09 0222:34.689117 Start Service Discovery (0x003a) plen 1 Status: Success (0x00) Address type: 0x06 LE Public LE Random @ MGMT Event: Discovering (0x0013) plen 2 {0x0001 [hci0] 2025-03-09 02:22:34.689133 Address type: 0x06 LE Public LE Random Discovery: Enabled (0x01) > HCI Event: LE Meta Event (0x3e) plen 41 #955839 [hci0] 2025-03-09 02:22:34.703348** LE Advertising Report (0x02) Num reports: 1 Event type: Connectable undirected - ADV_IND (0x00) Address type: Random (0x01) Address: DE:AA:24:9A:EE:7A (Static) Data length: 29 Flags: 0x06 LE General Discoverable Mode BR/EDR Not Supported Company: North Pole Engineering (816) Data: 8301 Name (complete): LF07aee9a24aade166 RSSI: -87 dBm (0xa9) > HCI Event: LE Meta Event (0x3e) plen 41 #955840 [hci0] 2025-03-09 02:22:34.706274 LE Advertising Report (0x02) Num reports: 1 Event type: Scan response - SCAN_RSP (0x04) Address type: Random (0x01) Address: DE:AA:24:9A:EE:7A (Static) Data length: 29 16-bit Service UUIDs (partial): 1 entry Fitness Machine (0x1826) 128-bit Service UUIDs (partial): 1 entry Vendor specific ... Data length: 25 Flags: 0x06 LE General Discoverable Mode BR/EDR Not Supported Name (complete): PSR110120 Company: SKF (U.K.) Limited (1038) Data: 00000000011601 RSSI: -47 dBm (0xd1) > HCI Event: LE Meta Event (0x3e) plen 12 #957115 [hci0] 2025-03-09 02:23:03.593462 LE Advertising Report (0x02) Num reports: 1 Event type: Scan response - SCAN_RSP (0x04) Address type: Public (0x00) Address: C4:BD:6A:11:01:20 (SKF GmbH) Data length: 0 RSSI: -47 dBm (0xd1) @ MGMT Event: Device Found (0x0012) plen 39 0x0001} [hci0] 2025-03-09 0223:03.593595 LE Address: C4:BD:6A:11:01:20 (SKF GmbH) RSSI: -47 dBm (0xd1) Flags: 0x00000000 Data length: 25 Flags: 0x06 LE General Discoverable Mode BR/EDR Not Supported Name (complete): PSR110120 Company: SKF (U.K.) Limited (1038) Data: 00000000011601 **@ MGMT Event: Discovering (0x0013) plen 2 {0x0001 [hci0] 2025-03-09 02:23:03.597941 Address type: 0x06 LE Public LE Random Discovery: Disabled (0x00) < HCI Command: LE Set Scan Enable (0x08|0x000c) plen 2 #957116 [hci0] 2025-03-09 02:23:03.598068 Scanning: Disabled (0x00) Filter duplicates: Disabled (0