How to Force LE Coded PHY S=8 (125 kbps) for Extended Advertising on nRF52840 with Zephyr/nRF Connect SDK?

RE: How to Force LE Coded PHY S=8 (125 kbps) for Extended Advertising on nRF52840 with Zephyr/nRF Connect SDK?

Hieu — Tue, 13 May 2025 16:57:54 GMT

While the HCI command encode the PHY as you said, the host converted it to a different encoding scheme. Please refer to:

https://github.com/nrfconnect/sdk-zephyr/blob/v4.0.99-ncs1/subsys/bluetooth/host/scan.c#L744-L764

If you want to confirm that is actually the case, here is the traceback:

In nrf/subsys/bluetooth/scan.c:

notify_filter_no_match()
>filter_state_check()
>>scan_recv
>>>struct bt_le_scan_cb .recv

In zephyr/subsys/bluetooth/host/scan.c

listener->recv
>le_adv_recv()
>>bt_hci_le_adv_ext_report(), where create_ext_adv_info() is used to prepare the scan report
>>>get_ext_adv_coding_sel_phy()

RE: How to Force LE Coded PHY S=8 (125 kbps) for Extended Advertising on nRF52840 with Zephyr/nRF Connect SDK?

Lorenz242 — Mon, 12 May 2025 13:24:56 GMT

I'm getting the PHY values from the primary_phy and secondary_phy members of device_info->recv_info (which is a const struct bt_le_scan_recv_info *) within the filter_no_match callback of the Nordic nrf_bt_scan API (using #include <bluetooth/scan.h>).

// From the scan_filter_no_match_cb:
// struct bt_scan_device_info *device_info;
// ...
if (gps_data_deserialize_from_adv(manuf_data_ptr, manuf_data_len,
                                  &received_manuf_id, &received_gps_data)) {
    if (received_manuf_id == GPS_TRACKER_MANUFACTURER_ID) {
        LOG_INF("GPS-Tag gefunden: %s, RSSI: %d dBm, PHY: Prim %u, Sec %u, TX-Power: %d dBm",
                addr_str,
                device_info->recv_info->rssi,
                device_info->recv_info->primary_phy, // This is what I'm logging as "Prim"
                device_info->recv_info->secondary_phy, // This is what I'm logging as "Sec"
                device_info->recv_info->tx_power);
    }
}

My interpretation of the logged 4 as S=2 (and 3 as S=8) is based on the Bluetooth Core Spec (v6.1, page 2357/ 2358)

RE: How to Force LE Coded PHY S=8 (125 kbps) for Extended Advertising on nRF52840 with Zephyr/nRF Connect SDK?

Hieu — Mon, 12 May 2025 12:14:22 GMT

Hi Lorenz242,

Which function are you using to extract the PHY value? A value of 4 doesn't necessarily mean S=2. For example, here it means Coded PHY with unspecified encoding: sdk-zephyr/include/zephyr/bluetooth/gap.h at v4.0.99-ncs1-1 · nrfconnect/sdk-zephyr.

Hieu