.. _faq_ble_phy:

How to set BLE PHY
##################

BLE PHY setting defaults to 1M. They can be set to 2M or CODED_S2 or CODED_S8 by using Zephyr supported APIs as explained below.

To set PHY rate, applications need to do the following:

Set these in Application's prj.conf file:

.. code-block:: kconfig

   CONFIG_BT_USER_PHY_UPDATE=y
   CONFIG_BT_PHY_UPDATE=y
   CONFIG_BT_AUTO_PHY_UPDATE=n

BLE PHY can be configured using Zephyr API ``bt_conn_le_phy_update()`` to the desired PHY value.

Here is a sample code reference:

.. code-block:: c

   /*
    * PHY Update: Configure the physical layer based on Kconfig selection
    * - 1M PHY: Standard BLE PHY with 1 Mbps data rate
    * - 2M PHY: Enhanced PHY with 2 Mbps data rate (better throughput)
    * - Coded PHY S2/S8: Long-range PHY with error correction (better range)
    */
   #if defined(CONFIG_ATM_BT_PHY_CODED_S2) || defined(CONFIG_ATM_BT_PHY_CODED_S8)
           static struct bt_conn_le_phy_param update_phy;
   #endif

   #if defined(CONFIG_ATM_BT_PHY_1M)
           err = bt_conn_le_phy_update(default_conn, BT_CONN_LE_PHY_PARAM_1M);
   #elif defined(CONFIG_ATM_BT_PHY_2M)
           err = bt_conn_le_phy_update(default_conn, BT_CONN_LE_PHY_PARAM_2M);
   #elif defined(CONFIG_ATM_BT_PHY_CODED_S2)
           update_phy.options = BT_CONN_LE_PHY_OPT_CODED_S2;
           update_phy.pref_rx_phy = BT_GAP_LE_PHY_CODED;
           update_phy.pref_tx_phy = BT_GAP_LE_PHY_CODED;
           err = bt_conn_le_phy_update(default_conn, &update_phy);
   #elif defined(CONFIG_ATM_BT_PHY_CODED_S8)
           update_phy.options = BT_CONN_LE_PHY_OPT_CODED_S8;
           update_phy.pref_rx_phy = BT_GAP_LE_PHY_CODED;
           update_phy.pref_tx_phy = BT_GAP_LE_PHY_CODED;
           err = bt_conn_le_phy_update(default_conn, &update_phy);
   #else
           LOG_INF("PHY mode not set in Kconfig");
           return;
   #endif

To get a Connection PHY update callback defined using the Zephyr facilities, insert code as below:

.. code-block:: c

   BT_CONN_CB_DEFINE(conn_callbacks) = {
           .connected = connected,
           .disconnected = disconnected,
           .le_phy_updated = le_phy_updated,
    };

   /**
    * @brief Callback for BLE PHY update completion
    *
    * @param conn Connection handle for the BLE connection
    * @param param PHY information containing new RX and TX PHY values
    */
   static void le_phy_updated(struct bt_conn *conn, struct bt_conn_le_phy_info *param)
   {
           LOG_INF("PHY UPDATED RX PHY %d, TX PHY %d", param->rx_phy, param->tx_phy);
   }

And Application's Kconfig can specify the configuration choice for PHY setting as follows:

.. code-block:: kconfig

   choice
       prompt "Select BLE PHY mode"
       default ATM_BT_PHY_1M

   config ATM_BT_PHY_1M
       bool "1M PHY"

   config ATM_BT_PHY_2M
       bool "2M PHY"

   config ATM_BT_PHY_CODED_S2
       bool "Coded PHY (S2)"

   config ATM_BT_PHY_CODED_S8
       bool "Coded PHY (S8)"

   endchoice