samples: usb: add UAC2 implicit feedback sample

doc/connectivity/usb/device/usb_device.rst

@@ -603,6 +603,8 @@ The following Product IDs are currently used:
 +----------------------------------------------------+--------+
 | :zephyr:code-sample:`uac2-explicit-feedback`       | 0x000E |
 +----------------------------------------------------+--------+
+| :zephyr:code-sample:`uac2-implicit-feedback`       | 0x000F |
++----------------------------------------------------+--------+
 | :zephyr:code-sample:`usb-dfu` (DFU Mode)           | 0xFFFF |
 +----------------------------------------------------+--------+
 

doc/connectivity/usb/device_next/usb_device.rst

@@ -55,6 +55,8 @@ Samples
 
 * :zephyr:code-sample:`uac2-explicit-feedback`
 
+* :zephyr:code-sample:`uac2-implicit-feedback`
+
 Samples ported to new USB device support
 ----------------------------------------
 

samples/subsys/usb/uac2_implicit_feedback/CMakeLists.txt

@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(usb_audio_async_i2s)
+
+include(${ZEPHYR_BASE}/samples/subsys/usb/common/common.cmake)
+target_sources(app PRIVATE src/main.c)
+
+if (CONFIG_SOC_COMPATIBLE_NRF5340_CPUAPP)
+	target_sources(app PRIVATE src/feedback_nrf53.c)
+else()
+	target_sources(app PRIVATE src/feedback_dummy.c)
+endif()

samples/subsys/usb/uac2_implicit_feedback/Kconfig

@@ -0,0 +1,9 @@
+# Copyright (c) 2023-2024 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+# Source common USB sample options used to initialize new experimental USB
+# device stack. The scope of these options is limited to USB samples in project
+# tree, you cannot use them in your own application.
+source "samples/subsys/usb/common/Kconfig.sample_usbd"
+
+source "Kconfig.zephyr"

samples/subsys/usb/uac2_implicit_feedback/README.rst

@@ -0,0 +1,41 @@
+.. zephyr:code-sample:: uac2-implicit-feedback
+   :name: USB Audio asynchronous implicit feedback sample
+   :relevant-api: usbd_api uac2_device i2s_interface
+
+   USB Audio 2 implicit feedback sample playing stereo and recording mono audio
+   on I2S interface.
+
+Overview
+********
+
+This sample demonstrates how to implement USB asynchronous bidirectional audio
+with implicit feedback. The host adjusts number of stereo samples sent for
+headphones playback based on the number of mono microphone samples received.
+
+Requirements
+************
+
+Target must be able to measure I2S block start (i.e. first sample from output
+buffer gets out) relative to USB SOF. The relative offset must be reported with
+single sample accuracy.
+
+This sample has been tested on :ref:`nrf5340dk_nrf5340`. While for actual audio
+experience it is necessary to connect external I2S ADC and I2S DAC, simple echo
+can be accomplished by shorting I2S data output with I2S data input.
+
+Theoretically it should be possible to obtain the timing information based on
+I2S and USB interrupts, but currently neither subsystem currently provides
+necessary timestamp information.
+
+Building and Running
+********************
+
+The code can be found in :zephyr_file:`samples/subsys/usb/uac2_implicit_feedback`.
+
+To build and flash the application:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/subsys/usb/uac2_implicit_feedback
+   :board: nrf5340dk/nrf5340/cpuapp
+   :goals: build flash
+   :compact:

samples/subsys/usb/uac2_implicit_feedback/app.overlay

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2023 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <dt-bindings/usb/audio.h>
+
+/ {
+	uac2_headset: usb_audio2 {
+		compatible = "zephyr,uac2";
+		status = "okay";
+		audio-function = <AUDIO_FUNCTION_HEADSET>;
+
+		uac_aclk: aclk {
+			compatible = "zephyr,uac2-clock-source";
+			clock-type = "internal-programmable";
+			frequency-control = "host-programmable";
+			sampling-frequencies = <48000>;
+		};
+
+		out_terminal: out_terminal {
+			compatible = "zephyr,uac2-input-terminal";
+			clock-source = <&uac_aclk>;
+			terminal-type = <USB_TERMINAL_STREAMING>;
+			front-left;
+			front-right;
+		};
+
+		headphones_output: headphones {
+			compatible = "zephyr,uac2-output-terminal";
+			data-source = <&out_terminal>;
+			clock-source = <&uac_aclk>;
+			terminal-type = <BIDIRECTIONAL_TERMINAL_HEADSET>;
+			assoc-terminal = <&mic_input>;
+		};
+
+		mic_input: microphone {
+			compatible = "zephyr,uac2-input-terminal";
+			clock-source = <&uac_aclk>;
+			terminal-type = <BIDIRECTIONAL_TERMINAL_HEADSET>;
+			/* Circular reference, macros will figure it out and
+			 * provide correct associated terminal ID because the
+			 * terminals associations are always 1-to-1.
+			 *
+			 * assoc-terminal = <&headphones_output>;
+			 */
+			front-left;
+		};
+
+		in_terminal: in_terminal {
+			compatible = "zephyr,uac2-output-terminal";
+			data-source = <&mic_input>;
+			clock-source = <&uac_aclk>;
+			terminal-type = <USB_TERMINAL_STREAMING>;
+		};
+
+		as_iso_out: out_interface {
+			compatible = "zephyr,uac2-audio-streaming";
+			linked-terminal = <&out_terminal>;
+			implicit-feedback;
+			subslot-size = <2>;
+			bit-resolution = <16>;
+		};
+
+		as_iso_in: in_interface {
+			compatible = "zephyr,uac2-audio-streaming";
+			linked-terminal = <&in_terminal>;
+			implicit-feedback;
+			subslot-size = <2>;
+			bit-resolution = <16>;
+		};
+	};
+};

samples/subsys/usb/uac2_implicit_feedback/boards/nrf5340dk_nrf5340_cpuapp.conf

@@ -0,0 +1,2 @@
+#Enable timer for asynchronous feedback
+CONFIG_NRFX_TIMER2=y

samples/subsys/usb/uac2_implicit_feedback/boards/nrf5340dk_nrf5340_cpuapp.overlay

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2023 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "../app.overlay"
+
+&pinctrl {
+	i2s0_default_alt: i2s0_default_alt {
+		group1 {
+			psels = <NRF_PSEL(I2S_SCK_M, 1, 15)>,
+				<NRF_PSEL(I2S_LRCK_M, 1, 12)>,
+				<NRF_PSEL(I2S_SDOUT, 1, 13)>,
+				<NRF_PSEL(I2S_SDIN, 1, 14)>;
+		};
+	};
+};
+
+&clock {
+	hfclkaudio-frequency = <12288000>;
+};
+
+i2s_rxtx: &i2s0 {
+	status = "okay";
+	pinctrl-0 = <&i2s0_default_alt>;
+	pinctrl-names = "default";
+	clock-source = "ACLK";
+};

samples/subsys/usb/uac2_implicit_feedback/prj.conf

@@ -0,0 +1,12 @@
+CONFIG_I2S=y
+
+#USB related configs
+CONFIG_USB_DEVICE_STACK_NEXT=y
+CONFIG_USBD_AUDIO2_CLASS=y
+CONFIG_SAMPLE_USBD_PID=0x000F
+CONFIG_SAMPLE_USBD_PRODUCT="UAC2 implicit feedback sample"
+
+#LOG subsystem related configs
+CONFIG_LOG=y
+CONFIG_USBD_LOG_LEVEL_WRN=y
+CONFIG_UDC_DRIVER_LOG_LEVEL_WRN=y

samples/subsys/usb/uac2_implicit_feedback/sample.yaml

@@ -0,0 +1,10 @@
+sample:
+  name: USB Audio 2 asynchronous implicit feedback sample
+tests:
+  sample.subsys.usb.uac2_implicit_feedback:
+    depends_on:
+      - usbd
+      - i2s
+    tags: usb i2s
+    platform_allow: nrf5340dk/nrf5340/cpuapp
+    harness: TBD

samples/subsys/usb/uac2_implicit_feedback/src/feedback.h

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef FEEDBACK_H_
+#define FEEDBACK_H_
+
+#include <stdint.h>
+
+/* Nominal number of samples received on each SOF. This sample is currently
+ * supporting only 48 kHz sample rate.
+ */
+#define SAMPLES_PER_SOF     48
+
+struct feedback_ctx *feedback_init(void);
+void feedback_reset_ctx(struct feedback_ctx *ctx);
+void feedback_process(struct feedback_ctx *ctx);
+void feedback_start(struct feedback_ctx *ctx, int i2s_blocks_queued);
+
+/* Return offset between I2S block start and USB SOF in samples.
+ *
+ * Positive offset means that I2S block started at least 1 sample after SOF and
+ * to correct the situation, shorter than nominal buffers are needed.
+ *
+ * Negative offset means that I2S block started at least 1 sample before SOF and
+ * to correct the situation, larger than nominal buffers are needed.
+ *
+ * Offset 0 means that I2S block started within 1 sample around SOF. This is the
+ * dominant value expected during normal operation.
+ */
+int feedback_samples_offset(struct feedback_ctx *ctx);
+
+#endif /* FEEDBACK_H_ */

samples/subsys/usb/uac2_implicit_feedback/src/feedback_dummy.c

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include "feedback.h"
+
+#warning "No target specific feedback code, overruns/underruns will occur"
+
+struct feedback_ctx *feedback_init(void)
+{
+	return NULL;
+}
+
+void feedback_process(struct feedback_ctx *ctx)
+{
+	ARG_UNUSED(ctx);
+}
+
+void feedback_reset_ctx(struct feedback_ctx *ctx)
+{
+	ARG_UNUSED(ctx);
+}
+
+void feedback_start(struct feedback_ctx *ctx, int i2s_blocks_queued)
+{
+	ARG_UNUSED(ctx);
+	ARG_UNUSED(i2s_blocks_queued);
+}
+
+int feedback_samples_offset(struct feedback_ctx *ctx)
+{
+	ARG_UNUSED(ctx);
+
+	/* Always send nominal number of samples */
+	return 0;
+}