tests: drivers: audio: Add test that collects audio from PDM microphone

Verify operation of PDM driver with physical microphone and
manual sound analysis.

Signed-off-by: Sebastian Głąb <[email protected]>

Author: nordic-segl

CODEOWNERS

@@ -832,6 +832,7 @@
 /tests/bluetooth/bsim/nrf_auraconfig/     @nrfconnect/ncs-audio
 /tests/bluetooth/tester/                  @carlescufi @nrfconnect/ncs-paladin
 /tests/crypto/                            @stephen-nordic @magnev
+/tests/drivers/audio/dmic_dump_buffer/    @nrfconnect/ncs-low-level-test
 /tests/drivers/audio/pdm_loopback/        @nrfconnect/ncs-low-level-test
 /tests/drivers/gpio/                      @nrfconnect/ncs-low-level-test @nrfconnect/ncs-ll-ursus
 /tests/drivers/flash/flash_ipuc/          @nrfconnect/ncs-charon

tests/drivers/audio/dmic_dump_buffer/CMakeLists.txt

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(dmic)
+
+target_sources(app PRIVATE src/main.c)

tests/drivers/audio/dmic_dump_buffer/Kconfig

@@ -0,0 +1,14 @@
+#
+# Copyright (c) 2025 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+source "Kconfig.zephyr"
+
+config TEST_USE_DMM
+	bool "Use of DMM pre-allocation"
+	help
+	  The test will use it to determine whether to prealocate DMM
+	  buffer or use regular mem slab and allocate dmm buffer inside
+	  PDM driver.

tests/drivers/audio/dmic_dump_buffer/README.txt

@@ -0,0 +1,28 @@
+This test uses DMIC driver to collect sound from PDM microphone.
+Audio samples are output on serial port @921600 bit/s in binary mode.
+
+
+Follow these steps to collect and analyse sound:
+
+1. Connect PDM microphone (tested with https://www.adafruit.com/product/3492) to PDM_CLK and PDM_DIN as defined in the board overlay.
+
+2. Compile and run dmic_dump_buffer test:
+   west build -b nrf54l15dk/nrf54l15/cpuapp --pristine --test-item drivers.audio.dmic_dump_buffer .
+   west flash --erase
+
+3. Store output from serial port to a file:
+   - press RESET button on DK to stop execution
+   - start data capture, f.e.
+     picocom -f n -b 921600 /dev/serial/by-id/usb-SEGGER_J-Link_00105xxx-if02 > /home/user/sound_capture.raw
+   - release RESET button
+
+4. Collect sound with the microphone. Then, stop data acquisition (f.e. Ctr+a, Ctrl+x)
+
+5. If using picocom, remove text at the beginning and at the end of the file (that is added by picocom).
+
+6. Convert end line symbols
+   dos2unix -f /home/user/sound_capture.raw
+
+7. Import raw data to Audacity (Signed 16-bit PCM; little-endian; mono; 16000Hz).
+
+This test is based on https://docs.zephyrproject.org/latest/samples/shields/x_nucleo_iks02a1/microphone/README.html

tests/drivers/audio/dmic_dump_buffer/boards/nrf52840dk_nrf52840.overlay

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+&pinctrl {
+	pdm0_default_alt: pdm0_default_alt {
+		group1 {
+			psels = <NRF_PSEL(PDM_CLK, 0, 30)>,
+				<NRF_PSEL(PDM_DIN, 0, 31)>;
+		};
+	};
+};
+
+dmic_dev: &pdm0 {
+	status = "okay";
+	pinctrl-0 = <&pdm0_default_alt>;
+	pinctrl-names = "default";
+	clock-source = "PCLK32M_HFXO";
+};
+
+&uart0 {
+	current-speed = < 921600 >;
+};

tests/drivers/audio/dmic_dump_buffer/boards/nrf5340dk_nrf5340_cpuapp.overlay

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+&clock {
+	hfclkaudio-frequency = <12288000>;
+};
+
+&pinctrl {
+	pdm0_default_alt: pdm0_default_alt {
+		group1 {
+			psels = <NRF_PSEL(PDM_CLK, 0, 25)>,
+				<NRF_PSEL(PDM_DIN, 0, 26)>;
+		};
+	};
+};
+
+dmic_dev: &pdm0 {
+	status = "okay";
+	pinctrl-0 = <&pdm0_default_alt>;
+	pinctrl-names = "default";
+	clock-source = "ACLK";
+};
+
+&uart0 {
+	current-speed = < 921600 >;
+};

tests/drivers/audio/dmic_dump_buffer/boards/nrf54h20dk_nrf54h20_cpuapp.overlay

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+&pinctrl {
+	pdm0_default_alt: pdm0_default_alt {
+		group1 {
+			psels = <NRF_PSEL(PDM_CLK, 1, 2)>,
+				<NRF_PSEL(PDM_DIN, 1, 4)>;
+		};
+	};
+};
+
+dmic_dev: &pdm0 {
+	status = "okay";
+	pinctrl-0 = <&pdm0_default_alt>;
+	pinctrl-names = "default";
+	clock-source = "PCLK32M";
+	memory-regions = <&cpuapp_dma_region>;
+};
+
+&uart136 {
+	current-speed = < 921600 >;
+};

tests/drivers/audio/dmic_dump_buffer/boards/nrf54l15dk_nrf54l15_cpuapp.overlay

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+&pinctrl {
+	pdm20_default_alt: pdm20_default_alt {
+		group1 {
+			psels = <NRF_PSEL(PDM_CLK, 1, 12)>,
+				<NRF_PSEL(PDM_DIN, 1, 13)>;
+		};
+	};
+};
+
+dmic_dev: &pdm20 {
+	status = "okay";
+	pinctrl-0 = <&pdm20_default_alt>;
+	pinctrl-names = "default";
+	clock-source = "PCLK32M";
+};
+
+&uart20 {
+	current-speed = < 921600 >;
+};

tests/drivers/audio/dmic_dump_buffer/prj.conf

@@ -0,0 +1,11 @@
+CONFIG_BOOT_BANNER=n
+CONFIG_NCS_BOOT_BANNER=n
+
+CONFIG_AUDIO=y
+CONFIG_AUDIO_DMIC=y
+
+CONFIG_LOG=n
+CONFIG_LOG_MODE_IMMEDIATE=n
+CONFIG_PRINTK=y
+
+CONFIG_MAIN_STACK_SIZE=16384

tests/drivers/audio/dmic_dump_buffer/src/main.c

@@ -0,0 +1,135 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+#include <string.h>
+#include <zephyr/kernel.h>
+#include <zephyr/audio/dmic.h>
+
+#if defined(CONFIG_HAS_NORDIC_DMM)
+#include <dmm.h>
+#endif
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(dmic_sample);
+
+#define SAMPLE_RATE  16000
+#define SAMPLE_BIT_WIDTH 16
+#define BYTES_PER_SAMPLE (SAMPLE_BIT_WIDTH / 8)
+#define NO_OF_CHANNELS	1
+
+/* Milliseconds to wait for a block to be captured by PCM peripheral. */
+#define READ_TIMEOUT     1200
+
+/* Driver will allocate blocks from this slab to receive audio data into them.
+ * Application, after getting a given block from the driver and processing its
+ * data, needs to free that block.
+ */
+#define AUDIO_BLOCK_SIZE   (BYTES_PER_SAMPLE * SAMPLE_RATE * NO_OF_CHANNELS / 40)
+/* Driver allocates memory "in advance" therefore 2 blocks may be not enough. */
+#define BLOCK_COUNT      4
+
+#if CONFIG_TEST_USE_DMM
+struct k_mem_slab mem_slab;
+char __aligned(WB_UP(4)) mem_slab_buffer[BLOCK_COUNT * WB_UP(AUDIO_BLOCK_SIZE)]
+					 DMM_MEMORY_SECTION(DT_NODELABEL(dmic_dev));
+#else
+K_MEM_SLAB_DEFINE_STATIC(mem_slab, AUDIO_BLOCK_SIZE, BLOCK_COUNT, 4);
+#endif
+
+int main(void)
+{
+	const struct device *const dmic_dev = DEVICE_DT_GET(DT_NODELABEL(dmic_dev));
+	int ret;
+	int loop_counter = 1;
+	void *buffer;
+	uint32_t size;
+
+	struct pcm_stream_cfg stream = {
+		.pcm_rate = SAMPLE_RATE,
+		.pcm_width = SAMPLE_BIT_WIDTH,
+		.block_size = AUDIO_BLOCK_SIZE,
+		.mem_slab  = &mem_slab,
+	};
+
+	struct dmic_cfg cfg = {
+		.io = {
+			/* These fields can be used to limit the PDM clock
+			 * configurations that the driver is allowed to use
+			 * to those supported by the microphone.
+			 */
+			.min_pdm_clk_freq = 1000000,
+			.max_pdm_clk_freq = 3250000,
+			.min_pdm_clk_dc   = 40,
+			.max_pdm_clk_dc   = 60,
+		},
+		.streams = &stream,
+		.channel = {
+			.req_num_chan = 1,
+			.req_num_streams = 1,
+			.req_chan_map_lo = dmic_build_channel_map(0, 0, PDM_CHAN_LEFT),
+		},
+	};
+
+	if (!device_is_ready(dmic_dev)) {
+		LOG_ERR("%s is not ready", dmic_dev->name);
+		return 0;
+	}
+
+#if CONFIG_TEST_USE_DMM
+	ret = k_mem_slab_init(&mem_slab, mem_slab_buffer, WB_UP(AUDIO_BLOCK_SIZE), BLOCK_COUNT);
+	if (ret < 0) {
+		LOG_ERR("Memory slab initialization failed, return code = %d", ret);
+		return ret;
+	}
+#endif
+
+	ret = dmic_configure(dmic_dev, &cfg);
+	if (ret < 0) {
+		LOG_ERR("Failed to configure the driver: %d", ret);
+		return ret;
+	}
+
+	ret = dmic_trigger(dmic_dev, DMIC_TRIGGER_START);
+	if (ret < 0) {
+		LOG_ERR("START trigger failed: %d", ret);
+		return ret;
+	}
+
+	while (1) {
+		ret = dmic_read(dmic_dev, 0, &buffer, &size, READ_TIMEOUT);
+		if (ret < 0) {
+			LOG_ERR("%d - read failed: %d", loop_counter, ret);
+			return ret;
+		}
+
+		/* Print buffer on serial port (in binary mode). */
+		unsigned char pcm_l, pcm_h;
+		int j;
+
+		uint16_t *pcm_out = buffer;
+
+		for (j = 0; j < size/2; j++) {
+			pcm_l = (char)(pcm_out[j] & 0xFF);
+			pcm_h = (char)((pcm_out[j] >> 8) & 0xFF);
+
+			z_impl_k_str_out(&pcm_l, 1);
+			z_impl_k_str_out(&pcm_h, 1);
+		}
+
+		k_mem_slab_free(&mem_slab, buffer);
+
+		loop_counter++;
+	}
+
+	/* Dead code; left for reference. */
+	ret = dmic_trigger(dmic_dev, DMIC_TRIGGER_STOP);
+	if (ret < 0) {
+		LOG_ERR("STOP trigger failed: %d", ret);
+		return ret;
+	}
+
+	return 0;
+}