boards: shields: add mchp_rnbd451_bt

boards/shields/mchp_rnbd451_bt/Kconfig.defconfig

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+# Copyright (c) 2025 Microchip Technology Inc.
+# SPDX-License-Identifier: Apache-2.0
+
+config MAIN_STACK_SIZE
+	default 2048 if BT_HOST_CRYPTO
+
+config BT_BUF_ACL_TX_COUNT
+	default 12
+
+config BT_BUF_EVT_RX_COUNT
+	default 13

boards/shields/mchp_rnbd451_bt/Kconfig.shield

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+# Copyright (c) 2025 Microchip Technology Inc.
+# SPDX-License-Identifier: Apache-2.0
+
+config SHIELD_MCHP_RNBD451_BT
+	def_bool $(shields_list_contains,mchp_rnbd451_bt)

boards/shields/mchp_rnbd451_bt/boards/sam_e54_xpro.overlay

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+/*
+ * Copyright (c) 2025 Microchip Technology Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+
+
+&sercom2{
+	current-speed = <115200>;
+};
+
+/*EXT1*/
+&pinctrl{
+	sercom0_uart_default: sercom0_uart_default {
+		group1 {
+			pinmux = <PA5D_SERCOM0_PAD1>,
+				 <PA4D_SERCOM0_PAD0>;
+		};
+	};
+};
+
+&sercom0{
+	status = "okay";
+	compatible = "microchip,sercom-g1-uart";
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	current-speed = <115200>;
+	data-bits = <8>;
+	parity = "none";
+	stop-bits = "1";
+
+	rxpo = <1>;
+	txpo = <0>;
+
+	pinctrl-0 = <&sercom0_uart_default>;
+	pinctrl-names = "default";
+};
+
+&nvmctrl{
+	status = "okay";
+};

boards/shields/mchp_rnbd451_bt/doc/index.rst

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+.. _rnbd451_add_on_shield:
+
+RNBD451 Add-on Board
+###############################
+
+Overview
+********
+
+The RNBD451 Add-on Board is an efficient low-cost development platform to evaluate and demonstrate
+the features, capabilities and interfaces of our Bluetooth® Low Energy module, RNBD451PE.
+The add-on board is compliant to the mikroBUS™ standard and includes an on-board MCP2200 USB-to-UART
+converter enabling out-of-box evaluation with no other hardware requirements.
+
+.. figure:: img/rnbd451-add-on-board.webp
+   :height: 350px
+   :align: center
+   :alt: RNBD451 Add-on Board
+
+   **Figure 1: RNBD451 Add-on Board**
+
+Requirements
+************
+
+This shield is compatible with a development board that includes a mikroBUS™ socket.
+If a mikroBUS socket is not available, a mikroBUS adapter can be used to provide both an
+extension header and a mikroBUS interface. The mikroBUS™ Xplained Pro is an extension Board
+for the Xplained Pro evaluation platform,  designed to support mikroBUS™ Click boards™ with
+Xplained Pro MCU boards.
+
+
+.. figure:: img/2080-atmbusadapter-xpro.webp
+   :height: 300px
+   :align: center
+   :alt: ATMBUSADAPTER-XPRO - mikroBUS Adapter
+
+   **Figure 2: ATMBUSADAPTER-XPRO - mikroBUS Adapter**
+
+
+Environment setup
+*****************
+
+Refer to "`Getting Started Guide
+<https://docs.zephyrproject.org/latest/develop/getting_started/index.html>`_"
+in "`Developing with Zephyr
+<https://docs.zephyrproject.org/latest/develop/index.html>`_"
+for installation instructions.
+After successful installation, the Zephyr SDK environment should be fully set up.
+All the sample applications listed here can be found in ``zephyrproject/zephyr/samples/bluetooth``,
+assuming the Zephyr SDK document is followed and the west workspace is named as "zephyrproject".
+
+.. note::
+
+  When bringing up the RNBD451 Bluetooth Low Energy (BLE) controller after a Power-On Reset (POR),
+  the Zephyr Bluetooth subsystem sends the **HCI reset command** (the first HCI command) to the BLE
+  controller. However, in the original design, this command is sent too early for the RNBD451, as
+  it takes approximately 4xx ms from POR to be ready to accept the first HCI command.
+
+  To address this timing issue, introduce a delay in the Zephyr application to enable Bluetooth.
+  This delay ensures that the **HCI reset command** is sent at the appropriate time. Add the following
+  code snippet to the application to introduce a 500 ms delay before calling ``bt_enable()``:
+
+  ``k_sleep(K_MSEC(500));``
+
+  Additionally, to prevent a voltage drop on the **extension header VCC pin**—which may cause the
+  RNBD451 to undergo a hardware reset after power-on; set **J100** to the **“BYPASS”** position. For more
+  information, refer to the `SAM E54 Xplained Pro Design Documentation (New Red PCB)`_.
+
+Hardware setting
+****************
+
+Using the SAM E54 Xplained Pro as an example, follow these steps to setup the hardware.
+
+#. Connect SAM E54 Xplained Pro Standard Extension Header (EXT1) with the mikroBUS Xplained Pro.
+#. Connect the RNBD451 to the mikroBUS Xplained Pro.
+#. Set the PWR_SEL jumper on the RNBD451 to Mikro 3V3 (to use power supplied by mikroBUS).
+#. Connect a USB cable to the Debug USB port.
+
+.. figure:: img/same54-with-rnbd451.webp
+   :align: center
+   :alt: RNBD451 Connected to ATMBUSADAPTER-XPRO and Mounted on SAM E54 Extension Header
+
+   **Figure 3: RNBD451 Connected to ATMBUSADAPTER-XPRO and Mounted on SAM E54 Extension Header**
+
+.. note::
+
+   When using a different Extension Header on the SAM E54 Xplained Pro, update the
+   ``rnbd451.overlay`` file accordingly.
+   For more details, refer to the  `SAM E54 Xplained Pro
+   User Guide`_.
+
+For more information about interfacing with the ATMBUSADAPTER-XPRO mikroBUS adapter,
+refer to the `RNBD451 Add-on Board Primary User Guide`_
+
+Sample application project configuration (prj.conf)
+***************************************************
+
+To select the HCI Host mode and the H4 driver, while disabling  the built-in controller,
+add the following configurations::
+
+   CONFIG_BT_HCI=y
+   CONFIG_BT_H4=y
+   CONFIG_BT_CTLR=n
+
+To disable Bluetooth Controller to Bluetooth Host flow control, which is not supported
+by RNBD451, add the following::
+
+   CONFIG_BT_HCI_ACL_FLOW_CONTROL=n
+
+To prevent the net-buffer from being drained during scan activity in the Central Multilink application, which can result in
+Controller unresponsive error, increase CONFIG_BT_BUF_EVT_DISCARDABLE_COUNT from 3 to 12.
+
+   CONFIG_BT_BUF_EVT_DISCARDABLE_COUNT=12
+
+
+Build the Applications
+**********************
+
+Navigate to the project root directory. For example, if the Zephyr workspace was setup
+following the Application Development section in the Zephyr Project Documentation,
+use the following command.
+
+``cd zephyrproject``
+
+Append the above mentioned ``prj.conf`` configurations to each ``prj.conf`` in Example #1~#5.
+Build the applications located in ``zephyr/samples/bluetooth`` using the following commands:
+
++----+---------------------+------------------------------------------------------------------------------------------------------------+
+| No | Example name        | Build command                                                                                              |
++====+=====================+============================================================================================================+
+| 1  | Peripheral          | west build -p always -b sam_e54_xpro --shield mchp_rnbd451_bt zephyr/samples/bluetooth/peripheral          |
++----+---------------------+------------------------------------------------------------------------------------------------------------+
+| 2  | HID Peripheral      | west build -p always -b sam_e54_xpro --shield mchp_rnbd451_bt zephyr/samples/bluetooth/peripheral_hids     |
++----+---------------------+------------------------------------------------------------------------------------------------------------+
+| 3  | Peripheral Identity | west build -p always -b sam_e54_xpro --shield mchp_rnbd451_bt zephyr/samples/bluetooth/peripheral_identity |
++----+---------------------+------------------------------------------------------------------------------------------------------------+
+| 4  | Central Multilink   | west build -p always -b sam_e54_xpro --shield mchp_rnbd451_bt zephyr/samples/bluetooth/central_multilink   |
++----+---------------------+------------------------------------------------------------------------------------------------------------+
+| 5  | Central/Gatt Write  | west build -p always -b sam_e54_xpro --shield mchp_rnbd451_bt zephyr/samples/bluetooth/central_gatt_write  |
++----+---------------------+------------------------------------------------------------------------------------------------------------+
+
+
+For more information on building the applications, refer to the `Building
+<https://docs.zephyrproject.org/latest/develop/west/build-flash-debug.html#building-west-build>`_
+section.
+
+Flash the Applications
+**********************
+To flash the built application, use the following command:
+
+``west flash``
+
+
+References
+**********
+
+.. target-notes::
+
+.. _SAM E54 Xplained Pro Design Documentation (New Red PCB):
+   https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/BoardDesignFiles/SAM-E54-Xplained-Pro-Design-Documentation-Rev11.zip
+
+.. _SAM E54 Xplained Pro User guide:
+   https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/UserGuides/70005321A.pdf
+
+.. _RNBD451 Add-on Board Primary User Guide:
+   https://ww1.microchip.com/downloads/aemDocuments/documents/WSG/ProductDocuments/UserGuides/RNBD451-Add-On-Board-User-Guide-DS50003476.pdf

boards/shields/mchp_rnbd451_bt/mchp_rnbd451_bt.overlay

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+/*
+ * Copyright (c) 2025 Microchip Technology Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	chosen {
+		zephyr,bt-hci = &bt_hci_uart;
+	};
+};
+
+&sercom0{
+	bt_hci_uart: bt_hci_uart {
+		compatible = "zephyr,bt-hci-uart";
+		status = "okay";
+	};
+};