Bluetooth: Samples: Add Connection event callback sample

The sample demonstrates how the connection event callback
feature can used to minimize latency between data sampling
and on air transmission.

Signed-off-by: Rubin Gerritsen <[email protected]>

samples/bluetooth/conn_evt_cb/CMakeLists.txt

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+#
+# Copyright (c) 2024 Nordic Semiconductor
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(NONE)
+
+zephyr_sources_ifdef(CONFIG_BT_CENTRAL src/central.c)
+zephyr_sources_ifdef(CONFIG_BT_PERIPHERAL src/peripheral.c)
+
+target_sources(app PRIVATE
+  src/main.c
+)

samples/bluetooth/conn_evt_cb/README.rst

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+.. _ble_conn_evt_cb:
+
+Bluetooth: Connection event callback
+#####################################
+
+.. contents::
+   :local:
+   :depth: 2
+
+The Connection event callback sample demonstrates how to use the connection event prepare callback feature described in :ref:`ug_bt_conn_evt_cb`.
+It uses the :ref:`latency_readme` and the :ref:`latency_client_readme` to showcase how this feature can be used to minimize the time between data sampling and data transmission.
+
+Requirements
+************
+
+The sample supports the following development kits:
+
+.. table-from-sample-yaml::
+
+You can use any two of the development kits mentioned above and mix different development kits.
+
+Additionally, the sample requires a connection to a computer with a serial terminal for each of the development kits.
+
+Note that the feature involves triggering a (D)PPI task directly from the SoftDevice Controller link layer, and therefore it is expected that the application and SoftDevice Controller are running on the same core.
+
+Building and running
+********************
+.. |sample path| replace:: :file:`samples/bluetooth/llpm`
+
+.. include:: /includes/build_and_run.txt
+
+Testing
+=======
+
+After programming the sample to both development kits, test it by performing the following steps:
+
+1. Connect to both kits with a terminal emulator (for example, `nRF Connect Serial Terminal`_).
+   See :ref:`test_and_optimize` for the required settings and steps.
+#. Reset both kits.
+#. In one of the terminal emulators, type "c" to start the application on the connected board in the central role.
+#. In the other terminal emulator, type "p" to start the application in the peripheral role.
+#. Observe that latency measurements are printed in the terminals.
+
+Sample output
+=============
+
+The result should look similar to the following output.
+
+- For the central::
+
+   Starting connection event callback sample.
+   I: SoftDevice Controller build revision:
+   I: d6 da c7 ae 08 db 72 6f |......ro
+   I: 2a a3 26 49 2a 4d a8 b3 |*.&I*M..
+   I: 98 0e 07 7f             |....
+   I: HW Platform: Nordic Semiconductor (0x0002)
+   I: HW Variant: nRF52x (0x0002)
+   I: Firmware: Standard Bluetooth controller (0x00) Version 214.51162 Build 1926957230
+   I: Identity: FA:BB:79:57:D6:45 (random)
+   I: HCI: version 5.4 (0x0d) revision 0x11fb, manufacturer 0x0059
+   I: LMP: version 5.4 (0x0d) subver 0x11fb
+   Choose device role - type c (central) or p (peripheral):
+   Central. Starting scanning
+   Scanning started
+   Device found: CF:99:32:A5:4B:11 (random) (RSSI -43)
+   Connected: CF:99:32:A5:4B:11 (random)
+   Service discovery completed
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1116 us, round trip latency: 51116 us
+
+- For the peripheral::
+
+   Starting connection event callback sample.
+   I: SoftDevice Controller build revision:
+   I: d6 da c7 ae 08 db 72 6f |......ro
+   I: 2a a3 26 49 2a 4d a8 b3 |*.&I*M..
+   I: 98 0e 07 7f             |....
+   I: HW Platform: Nordic Semiconductor (0x0002)
+   I: HW Variant: nRF52x (0x0002)
+   I: Firmware: Standard Bluetooth controller (0x00) Version 214.51162 Build 1926957230
+   I: Identity: CF:99:32:A5:4B:11 (random)
+   I: HCI: version 5.4 (0x0d) revision 0x11fb, manufacturer 0x0059
+   I: LMP: version 5.4 (0x0d) subver 0x11fb
+   Choose device role - type c (central) or p (peripheral):
+   Peripheral. Starting advertising
+   Advertising started
+   Connected: FA:BB:79:57:D6:45 (random)
+   Service discovery completed
+   Latency: 1666 us, round trip latency: 51666 us
+   Latency: 1086 us, round trip latency: 51086 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1086 us, round trip latency: 51086 us
+   Latency: 1666 us, round trip latency: 51666 us
+   Latency: 1086 us, round trip latency: 51086 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1116 us, round trip latency: 51116 us
+   Latency: 1666 us, round trip latency: 51666 us
+
+Dependencies
+*************
+
+This sample uses the following |NCS| libraries:
+
+* :ref:`latency_readme`
+* :ref:`latency_client_readme`
+
+This sample uses the following `sdk-nrfxlib`_ libraries:
+
+* :ref:`nrfxlib:softdevice_controller`
+
+In addition, it uses the following Zephyr libraries:
+
+* :file:`include/console.h`
+* :ref:`zephyr:kernel_api`:
+
+  * :file:`include/kernel.h`
+
+* :file:`include/sys/printk.h`
+* :file:`include/zephyr/types.h`
+* :ref:`zephyr:bluetooth_api`:
+
+  * :file:`include/bluetooth/bluetooth.h`
+  * :file:`include/bluetooth/conn.h`
+  * :file:`include/bluetooth/gatt.h`
+  * :file:`include/bluetooth/scan.h`
+  * :file:`include/bluetooth/gatt_dm.h`
+  * :file:`include/bluetooth/conn_evt_prepare_cb.h`

samples/bluetooth/conn_evt_cb/prj.conf

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+#
+# Copyright (c) 2024 Nordic Semiconductor
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+CONFIG_NCS_SAMPLES_DEFAULTS=y
+
+CONFIG_BT_DEVICE_NAME="Conn evt cb"
+CONFIG_BT=y
+CONFIG_BT_CONN_EVT_CB=y
+CONFIG_BT_PERIPHERAL=y
+CONFIG_BT_CENTRAL=y
+CONFIG_BT_MAX_CONN=2
+CONFIG_BT_CTLR_SDC_PERIPHERAL_COUNT=1
+CONFIG_BT_LATENCY=y
+CONFIG_BT_LATENCY_CLIENT=y
+CONFIG_BT_GATT_DM=y
+
+CONFIG_CONSOLE=y
+CONFIG_CONSOLE_SUBSYS=y
+CONFIG_CONSOLE_HANDLER=y
+CONFIG_CONSOLE_GETCHAR=y
+
+CONFIG_HEAP_MEM_POOL_SIZE=2048

samples/bluetooth/conn_evt_cb/sample.yaml

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+sample:
+  description: Connection event callback sample
+  name: Connection event callback
+tests:
+  sample.bluetooth.conn_evt_cb:
+    sysbuild: true
+    build_only: true
+    integration_platforms:
+      - nrf52dk/nrf52832
+      - nrf52840dk/nrf52840
+      - nrf5340dk/nrf5340/cpunet
+    platform_allow: nrf52dk/nrf52832 nrf52840dk/nrf52840 nrf5340dk/nrf5340/cpunet
+    tags: bluetooth ci_build sysbuild

samples/bluetooth/conn_evt_cb/src/central.c

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+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+#include <zephyr/bluetooth/bluetooth.h>
+#include <zephyr/bluetooth/conn.h>
+
+#define ADV_NAME_STR_MAX_LEN (sizeof(CONFIG_BT_DEVICE_NAME))
+
+void scan_start(void);
+
+static bool adv_data_parse_cb(struct bt_data *data, void *user_data)
+{
+	char *name = user_data;
+	uint8_t len;
+
+	switch (data->type) {
+	case BT_DATA_NAME_SHORTENED:
+	case BT_DATA_NAME_COMPLETE:
+		len = MIN(data->data_len, ADV_NAME_STR_MAX_LEN - 1);
+		memcpy(name, data->data, len);
+		name[len] = '\0';
+		return false;
+	default:
+		return true;
+	}
+}
+
+static void device_found(const bt_addr_le_t *addr, int8_t rssi, uint8_t type,
+			 struct net_buf_simple *ad)
+{
+	char name_str[ADV_NAME_STR_MAX_LEN] = {0};
+	char addr_str[BT_ADDR_LE_STR_LEN];
+	int err;
+
+	/* We're only interested in connectable events */
+	if (type != BT_GAP_ADV_TYPE_ADV_IND &&
+	    type != BT_GAP_ADV_TYPE_ADV_DIRECT_IND) {
+		return;
+	}
+
+	bt_data_parse(ad, adv_data_parse_cb, name_str);
+
+	if (strncmp(name_str, CONFIG_BT_DEVICE_NAME, ADV_NAME_STR_MAX_LEN) != 0) {
+		return;
+	}
+
+	bt_addr_le_to_str(addr, addr_str, sizeof(addr_str));
+	printk("Device found: %s (RSSI %d)\n", addr_str, rssi);
+
+	if (bt_le_scan_stop()) {
+		return;
+	}
+
+	struct bt_conn *unused_conn;
+
+	err = bt_conn_le_create(addr, BT_CONN_LE_CREATE_CONN,
+				BT_LE_CONN_PARAM_DEFAULT, &unused_conn);
+	if (err) {
+		printk("Create conn to %s failed (%d)\n", addr_str, err);
+		scan_start();
+	}
+}
+
+void scan_start(void)
+{
+	int err;
+
+	err = bt_le_scan_start(BT_LE_SCAN_ACTIVE, device_found);
+	if (err) {
+		printk("Scanning failed to start (err %d)\n", err);
+		return;
+	}
+
+	printk("Scanning started\n");
+}