Concurrent BIS and PAwR when using PAST

[Rai]

Dear Team, 

Is it possible to run BIS and PAwR concurrently while using PAST for synchronization? 
I am using the nRF52840 DK and NCS 2.8.

I managed to start two periodic advertising trains (BIS and PAwR) concurrently without any issues (both are working as expected). However, when I attempt to create a connection to a peer device (for PAST) afterwards, it fails with error 0x0C (command disallowed).

After some debugging, I may have found the cause of this problem. To support PAwR, the configuration CONFIG_BT_PER_ADV_RSP is required. This configuration extends the struct bt_le_per_adv_param with fields related to PAwR. When setting the parameters for my periodic advertisements used for BIS, I initially set those values to zero, as I do not need them (which works without problems). However, when doing so I cannot connect with any device anymore. If I set those values to meaningful numbers, I can successfully establish a connection again, but I can no longer create a BIG (as I now have two PAwR trains).

Note: The advertising does not need to be started to resolve this issue; it is sufficient to set the parameters using bt_le_per_adv_set_param() and set the PAwR related fileds of bt_le_per_adv_param to zero.

This issue can be recreated by using the existing zephyr sample (zephyr/samples/bluetooth): periodic_adv_rsp & periodic_sync_rsp.

Just change the periodic advertising parameters in main.c of the periodic_adv_rsp sample to: 

static const struct bt_le_per_adv_param per_adv_params = {
  .interval_min = 0xFF,
  .interval_max = 0xFF,
  .options = 0,
  .num_subevents = 0,
  .subevent_interval = 0,
  .response_slot_delay = 0,
  .response_slot_spacing = 0,
  .num_response_slots = 0,
};

As result, a connection cannot be established anymore: 

*** Booting nRF Connect SDK v2.8.0-a2386bfc8401 ***
*** Using Zephyr OS v3.7.99-0bc3393fb112 ***
Starting Periodic Advertising Demo
[00:00:00.000,671] <inf> bt_sdc_hci_driver: SoftDevice Controller build revision: 
                                            fe 2c f9 6a 7f 36 22 2e  a0 79 c0 40 be 2c 03 20 |.,.j.6". .y.@.,. 
                                            40 c2 f3 32                                      |@..2             
[00:00:00.003,021] <inf> bt_hci_core: HW Platform: Nordic Semiconductor (0x0002)
[00:00:00.003,051] <inf> bt_hci_core: HW Variant: nRF52x (0x0002)
[00:00:00.003,082] <inf> bt_hci_core: Firmware: Standard Bluetooth controller (0x00) Version 254.63788 Build 573996906
[00:00:00.003,997] <inf> bt_hci_core: Identity: E7:C1:B9:C8:AB:0B (random)
[00:00:00.004,058] <inf> bt_hci_core: HCI: version 6.0 (0x0e) revision 0x104e, manufacturer 0x0059
[00:00:00.004,089] <inf> bt_hci_core: LMP: version 6.0 (0x0e) subver 0x104e
Start Periodic Advertising
Start Extended Advertising
Scanning successfully started
[00:00:00.219,116] <wrn> bt_hci_core: opcode 0x2043 status 0x0c 
Create conn to ø$ failed (4294967283)

Thanks, 

Rainer

[runsiv]

Hi

I'm looking into the issue and I hope to get back to you tomorrow. 

Regards

Runar

[runsiv]

Just to verify, is the BIG from PAwR? SDC does not support creating a BIG from a PAwR train, which explains why it would fail. Setting num_subevents=0 will create a "normal" PADVB from which you can  can create a BIG. 

Regards

Runar

[Rai]

Hi Runar,
Thank you for addressing this issue.

No, the BIG is created from a standard PADVB (I have set the num_subevents=0), and there are no issues during its creation. However, after creating the BIG (when setting num_subevents=0 and CONFIG_BT_PER_ADV_RSP=y), I am unable to establish a connection to another device, as mentioned in the example above.

For context, I currently have one PAwR and one BIS running without any problems. My goal is to connect to a peer device to send synchronization information via PAST.

Regards,
Rainer

[runsiv]

Hi and thanks for the clarification 

Our softdevice team has looked into it made this workaround for you which should fix the issue for you while they investigate a bit. 

diff --
git a/samples/bluetooth/periodic_adv_rsp/src/main.c b/samples/bluetooth/periodic_adv_rsp/src/main.c
index 37d04306246..f42d651facc 100644
--- a/samples/bluetooth/periodic_adv_rsp/src/main.c
+++ b/samples/bluetooth/periodic_adv_rsp/src/main.c
@@ -10,6 +10,8 @@
 #include <zephyr/bluetooth/gatt.h>
 #include <zephyr/bluetooth/hci.h>
 
+#include <sdc_hci_vs.h>
+
 #define NUM_RSP_SLOTS 5
 #define NUM_SUBEVENTS 5
 #define PACKET_SIZE   5
@@ -27,11 +29,11 @@ static const struct bt_le_per_adv_param per_adv_params = {
        .interval_min = 0xFF,
        .interval_max = 0xFF,
        .options = 0,
-       .num_subevents = NUM_SUBEVENTS,
-       .subevent_interval = 0x30,
-       .response_slot_delay = 0x5,
-       .response_slot_spacing = 0x50,
-       .num_response_slots = NUM_RSP_SLOTS,
+       .num_subevents = 0,
+       .subevent_interval = 0,
+       .response_slot_delay = 0,
+       .response_slot_spacing = 0,
+       .num_response_slots = 0,
 };
 
 static struct bt_le_per_adv_subevent_data_params subevent_data_params[NUM_SUBEVENTS];
@@ -264,6 +266,14 @@ int main(void)
                return 0;
        }
 
+
+       sdc_hci_cmd_vs_allow_parallel_connection_establishments_t parallel_params = {.enable = 1};
+       err = sdc_hci_cmd_vs_allow_parallel_connection_establishments(&parallel_params);
+       if (err) {
+               printk("Failed to allow parallel connection establishment (err %d)\n", err);
+               return 0;
+       }
+
        /* Create a non-connectable advertising set */
        err = bt_le_ext_adv_create(BT_LE_EXT_ADV_NCONN, &adv_cb, &pawr_adv);
        if (err) {
 

Regards

Runar

[Rai]

Thank you! This fix worked for me.
Will this issue be addressed in a future update?

[runsiv]

Just an update on the fix: It will be merged into the NCS in the next nrfxlib-update so I would presume in maybe a release or two of NCS(not counting the one from last night). 

Regards

Runar