Hello Nordic Team,
We are using nRF52840 ble chip with S140 nordic stack and SDK 15.2.0 on the SEGGER IDE installed on the Windows OS. We want nRF52840 chip to detect surrounding mobile devices and also nRF52840 can fetch MAC addresses of mobile devices during scanning. We would like to know from your side that whether this is feasible or not ?. If yes, then can you please suggest us how to do it.
We are looking forward to hear from you.
Thanks
Bharat Gopani
Lumium Design
India.
Hello Einar,
Thank you very much for your support.
Where bonding initiated by smart phone is detected in the stack ? and which stack nRF52840 should use either peripheral or central ?
Let's assume that android phone is bonded with nRF52840, How we can get IRK from the event handler ??
Can we channge bluetooth range from 9 meters to 5 meters ?
Regards
Bharat
Hi,
Bharat said:Where bonding initiated by smart phone is detected in the stack ?
When acting as a peripheral, the nRF has to start connectable advertising. Then a central can connect, which is signaled to the device (see Peripheral Connection Establishment and Termination). Subsequently pairing/bonding can be initiated by either peer, in several ways. See Peripheral Security Procedures. Handling pairing and bonding is quite complex, so I do not recommend that you use the SoftDevice APIs directly. Instead, you should use the peer manager, as is also done in all BLE peripheral examples in the SDK that support connections.
Bharat said:Let's assume that android phone is bonded with nRF52840, How we can get IRK from the event handler ??
The IRK is exchanged during the bonding procedure and stored in flash by the peer manager, and can be obtained from there. The Peer manager also supports resolving MAC addresses, so that you can see if the MAC represents the device you are searching for (pm_address_resolve()). This can also be done in HW by the radio if you use whitelisting, but that does not seem sensible in a product where you want to scan and track any device.
Bharat said:Can we channge bluetooth range from 9 meters to 5 meters ?
You cannot determine the range on such exact levels. Rang depends on a lot of of the product which you can control fairly good: PCB layout, antenna, antenna matching, housing etc. There is also a significant chip-to-chip variation. Then there is factors that is difficult to control. How is the product positioned in the environment? Is it covered by a human some times? is there line of sight, or are there reflections? This tends to change all the time in a real world situation.
However, you can influence the range of transmitted signals by selection a lower TW power. For receiving signals (as this case is about a device scanning for mobile phones which are advertising), you have no such method. However the scan report from the SoftDevice will include the RSSI, which is the power of the received signal. You can chose to filter out signals with a low RSSI in your application based on that.
Hi Einar,
Thanks for your support.
1 . We have tried peer manager programs like ble_app_proximity and ble_app_hids_keyboard, , however it connects initially and disconnects immediately.
We are using nRF UART v2.0 to connect with nRF52840.
What coud be possible reason for this ??
2. In ble_app_uart pheripheral example, Device manager is used instead of peer manager. can you guide us for implementing peer manager in place of device manager ?
It would be helpful if you could guide us for the above.
Regards
Bharat
Hi,
Bharat said:What coud be possible reason for this ??
On the nRF side, you sould get a disconnect reason indicating why. A typical reason for the nRF or phone to disconnect when you use bonding is if you have deleted bonding information on one side. In that case, you will either see that the peer attempts to encrypt the link, but the bond does not exist on the other side. Alternatively the peer with no bonding information will try to bond, but the peer will refuse bonding as it is allready bonded. You should make sure to delete bonding information on both sides in this case, or alternatively configure the nRF to allow repairing.
Bharat said:
2. In ble_app_uart pheripheral example, Device manager is used instead of peer manager. can you guide us for implementing peer manager in place of device manager ?
It would be helpful if you could guide us for the above.
The device manager is legacy software and is no longer supported, and should not be used. It does not exist in any SDK with production support for nRF52840 (>= 15.0.0).
Thanks for the suggestions.
We have gone through ble_app_proximity example for understanding of peer manager and found that pm_evt_handler is event handler during bonding.
How can we get MAC address of the connected device from this event handler ??
Regards
Bharat
Thanks for the suggestions.
We have gone through ble_app_proximity example for understanding of peer manager and found that pm_evt_handler is event handler during bonding.
How can we get MAC address of the connected device from this event handler ??
Regards
Bharat
Hi,
If you are acting as peripheral you will get the MAC address of the connected central in the BLE event handler (ble_evt_handler() in most SDK examples) when it handles the BLE_GAP_EVT_CONNECTED event. You should find it as something like p_ble_evt->gap_evt.connected.peer_addr.addr, as a 6 byte uint8_t array.
Thanks for the reply.
This way we get an private resolvable address of the connected device but how we can get public address(MAC) using IRK and peer manager.
Regards
Bharat
You cannot get the MAC address of the peer from the IRK directly. However, you can resolve the MAC address based on the IRK. That is: when you have obtained both the IRK and a MAC address of the peer you can verify that the MAC address is derived from the IRK. So, when the MAC address change, you can resolve it again and know that even if it changed, it was from the same peer (same IRK).
Thank you very much.
Could you please elaborate resolving process for the peer address ?
If peer address changes and if we resolves it again then how can we come conclude that it is same peer ?
where can we get the IRK in the stack ?
Regards
Bharat
If you use whitelist scanning, then this can be handled by the AAR peripheral, but it would filter out any other advertising packets, so this is probably not what you want if I understood your use case correct (track any BLE advertisers in range). Therefor you probably want to use pm_address_resolve(), and iterate over all IRK you have in the list of bonded devices. You can get a list of all bonds using pm_peer_id_list().
