I currently need to solve pairing/bonding to be able to implement DFU with the buttonless bonded bootloader. So I need to handle bonding/pairing from my central device, controlled using pc-ble-driver (and connectivity firmware SD 140, v6.1.1). The project is at a late stage. Scanning, connecting, discovering and using characteristics is already really stable and works as expected.
Just a side note: The peripheral firmware seems to be correct, as I'm able to do DFU from a mobile application running on Android!
What already works:
After a connection to an unbonded peripheral is established (just before discovering services), I call sd_ble_gap_authenticate() with:
const ble_gap_sec_params_t SecurityParams = {
1, // Bond
0,
0,
0,
BLE_GAP_IO_CAPS_NONE,
0,
7,
16,
{ 1, 1, 0, 0 },
{ 1, 1, 0, 0 }
};
which responds with BLE_GAP_EVT_SEC_PARAMS_REQUEST. I answer this by calling sd_ble_gap_sec_params_reply(sec_status=0, p_sec_params=NULL, keySet), where keySet is just an empty buffer. This call fills the own/p_id_key with key data, which I store in a file. I than got BLE_GAP_EVT_AUTH_STATUS with bonded=true and auth_status=0 (SUCCESS).
At this point, I'm able to subscribe to BLE_DFU_BUTTONLESS_BONDED_CHAR_UUID's indication, so I assume bonding was successful. I can repeat this by resetting the bonding information in the peripheral.
What does not work:
I'm not able to recreate this state if the peripheral holds the bonding information. After the connection has been established I directly got BLE_GAP_EVT_SEC_REQUEST. Upon receiving this event, I call sd_ble_gap_authenticate() using the parameters above (tested with bond=0 and bond=1). I've also tested calling sd_ble_gap_authenticate() a second time after handling BLE_GAP_EVT_SEC_REQUEST. Either case, I always receive BLE_GAP_EVT_AUTH_STATUS with bonded=false and auth_status=133 (BLE_GAP_SEC_STATUS_PAIRING_NOT_SUPP). So I neither got BLE_GAP_EVT_SEC_PARAMS_REQUEST to supply my stored keys to the central.
I've tried to understand how pc-nrfutil handles this, but looking into github.com/.../dfu_transport_ble.py , def bond(), seems to do it this way too. I've no idea what I do wrong.
What's the correct way to connect / pair / (reestablish-)bond to an already bonded peripheral?
A second question: Does the connectivity firmware store the bonding keys on device site too? This question is centered about the usability. If I connect my central device to a different host PC and try to connect to an already bonded peripheral, does the central know the bonding keys (e.g. stored in flash) or do I have to copy my host site keystore to the new host (and supply them when receiving BLE_GAP_EVT_SEC_REQUEST)?
Many thanks,
Thomas
