Extend number of devices for PAwR (Coded PHY)

[Yannch]

Hi all !

I'm writing this message because I'm having problems trying to increase the number of devices in PAwR (I use Coded PHY).

I based my development on the SDK 2.8.0 example (Periodic_adv_conn / Periodic_sync_conn). I also tried Periodic_adv_rsp / Periodic_sync_rsp examples without success.

I've modified it so that I don't have to connect every time via on the TX side:

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bt_conn_le_create_synced function()

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bt_conn_le_create_synced function()

On the RX side, I have a fixed subevent and slot numbers to answer to TX.

Based on SDK example, I can exchange data with 25 devices (5 subevents / 5 slots)

I used the following configuration:

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#define NUM_RSP_SLOTS 5

#define NUM_SUBEVENTS 5

#define SUBEVENT_INTERVAL 0x30

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 = SUBEVENT_INTERVAL,

.response_slot_delay = 0x5,

.response_slot_spacing = 0x50,

.num_response_slots = NUM_RSP_SLOTS,

};

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#define NUM_RSP_SLOTS 5
#define NUM_SUBEVENTS 5
#define SUBEVENT_INTERVAL 0x30

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 = SUBEVENT_INTERVAL,
	.response_slot_delay = 0x5,
	.response_slot_spacing = 0x50,
	.num_response_slots = NUM_RSP_SLOTS,
};

When I try to increase the number of devices (8 subevents / 20 slots per subevent), I don't get the same behavior.

Below are the timings I use depending on the number of subevents and slots.

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#define NUM_RSP_SLOTS 20

#define NUM_SUBEVENTS 8

static const struct bt_le_per_adv_param per_adv_params = {

.interval_min = 0x960,

.interval_max = 0x960,

.options = 0,

.num_subevents = NUM_SUBEVENTS,

.subevent_interval = 0xF0,

.response_slot_delay = 0x10,

.response_slot_spacing = 0x50,

.num_response_slots = NUM_RSP_SLOTS,

};

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#define NUM_RSP_SLOTS 20
#define NUM_SUBEVENTS 8

static const struct bt_le_per_adv_param per_adv_params = {
	.interval_min = 0x960,
	.interval_max = 0x960,
	.options = 0,
	.num_subevents = NUM_SUBEVENTS,
	.subevent_interval = 0xF0,
	.response_slot_delay = 0x10,
	.response_slot_spacing = 0x50,
	.num_response_slots = NUM_RSP_SLOTS,
};

I saw that the PAwR feature is still experimental in the las version of the SDK, could this be related or is there something I'm doing wrong?

Thank you in advance for your answers or feedbacks.

Yann