bluetooth: samples: Add sample showing basic channel sounding features

This sample demonstrates how to use the CS test command.
It can be used to override randomization of certain parameters,
experiment with different CS configurations, and evaluate the RF medium.

A basic distance estimation method using phase rotations of the
unmodulated tones is included.

Signed-off-by: Olivier Lesage <olivier.lesage@nordicsemi.no>

include/zephyr/bluetooth/cs.h

@@ -540,6 +540,35 @@ struct bt_le_cs_subevent_step {
 	const uint8_t *data;
 };
 
+/** Sign-extended IQ sample extracted from step data. */
+struct bt_le_cs_iq_sample {
+	int16_t i;
+	int16_t q;
+};
+
+/** @brief Extract IQ sample from HCI-formatted PCT.
+ *
+ * Convenience function for processing 24-bit phase correction terms found
+ * in CS step data. The 12-bit signed real and imaginary components are
+ * converted to host endianness and sign-extended.
+ *
+ * @param pct 24-bit little-endian phase correction term.
+ *
+ * @return Real and imaginary terms as int16_t.
+ */
+static inline struct bt_le_cs_iq_sample bt_le_cs_parse_pct(const uint8_t pct[3])
+{
+	uint32_t sample = sys_get_le24(pct);
+	int16_t i;
+	int16_t q;
+	struct {
+		int16_t x: 12;
+	} s;
+	i = s.x = sample & BT_HCI_LE_CS_PCT_MASK;
+	q = s.x = (sample >> 12) & BT_HCI_LE_CS_PCT_MASK;
+	return (struct bt_le_cs_iq_sample){.i = i, .q = q};
+}
+
 /** @brief Set all valid channel map bits
  *
  * This command is used to enable all valid channels in a

samples/bluetooth/channel_sounding_test/CMakeLists.txt

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(channel_sounding_test)
+
+target_sources(app PRIVATE src/main.c)

samples/bluetooth/channel_sounding_test/README.rst

@@ -0,0 +1,28 @@
+.. _bluetooth-channel-sounding-test-sample:
+
+Bluetooth: Channel Sounding Testmode
+####################################
+
+Overview
+********
+
+This sample demonstrates how to use the CS test command.
+It can be used to override randomization of certain channel sounding parameters,
+experiment with different configurations, or evaluate the RF medium.
+
+A basic distance estimation method using phase rotations of the
+unmodulated tones is included.
+
+Requirements
+************
+
+* A board with BLE support
+* A controller that supports the Channel Sounding feature
+
+Building and Running
+********************
+
+This sample can be found under :zephyr_file:`samples/bluetooth/channel_sounding_test` in
+the Zephyr tree.
+
+See :zephyr:code-sample-category:`bluetooth` samples for details.

samples/bluetooth/channel_sounding_test/prj.conf

@@ -0,0 +1,23 @@
+CONFIG_CONSOLE=y
+CONFIG_CONSOLE_SUBSYS=y
+CONFIG_CONSOLE_HANDLER=y
+CONFIG_CONSOLE_GETCHAR=y
+
+CONFIG_BT=y
+CONFIG_BT_CENTRAL=y
+CONFIG_BT_PERIPHERAL=y
+CONFIG_BT_GATT_CLIENT=y
+CONFIG_BT_GATT_DYNAMIC_DB=y
+CONFIG_BT_CHANNEL_SOUNDING=y
+CONFIG_BT_CHANNEL_SOUNDING_TEST=y
+CONFIG_LOG=y
+
+CONFIG_BT_BUF_EVT_RX_SIZE=255
+CONFIG_BT_BUF_ACL_RX_SIZE=251
+CONFIG_BT_BUF_ACL_TX_SIZE=251
+CONFIG_BT_L2CAP_TX_MTU=247
+
+CONFIG_MAIN_STACK_SIZE=4096
+
+CONFIG_LOG_BUFFER_SIZE=2048
+CONFIG_CBPRINTF_FP_SUPPORT=y

samples/bluetooth/channel_sounding_test/sample.yaml

@@ -0,0 +1,11 @@
+sample:
+  name: Bluetooth Channel Sounding Test
+tests:
+  sample.bluetooth.channel_sounding_test:
+    harness: bluetooth
+    platform_allow:
+      - qemu_cortex_m3
+      - qemu_x86
+    tags: bluetooth
+    integration_platforms:
+      - qemu_cortex_m3