audio: add timestamp to raw files

microphone/drv_audio_pdm.c

@@ -18,6 +18,7 @@
 #include "storage.h"
 #include "audio_switch.h"
 #include "sampling_lib.h"
+#include "systick_lib.h"
 
 ret_code_t err_code;
 
@@ -29,13 +30,13 @@ nrf_pdm_mode_t local_mode;
 uint32_t local_freq;
 uint8_t local_gain_l;
 uint8_t local_gain_r;
-
+uint64_t timestamp_buffer[PDM_BUF_NUM] = {0};
 
 int16_t subsampled[PDM_BUF_SIZE/DECIMATION];
 float filter_weight[DECIMATION];
+static uint64_t recording_start_timestamp;
 
-
-static void process_audio_buffer(void)
+static void process_audio_buffer(uint8_t buffer_index)
 {
 	switch (audio_switch_position)
 	{
@@ -47,6 +48,7 @@ static void process_audio_buffer(void)
 		{
 			data_source_info.data_source = AUDIO;
 			data_source_info.audio_source_info.audio_buffer_length = PDM_BUF_SIZE*2;
+			data_source_info.audio_source_info.buffer_index = buffer_index;
 			err_code = app_sched_event_put(&data_source_info, sizeof(data_source_info), sd_write);
 			APP_ERROR_CHECK(err_code);
 		}
@@ -69,6 +71,7 @@ static void process_audio_buffer(void)
 			}
 
 			data_source_info.data_source = AUDIO;
+			data_source_info.audio_source_info.buffer_index = buffer_index;
 			data_source_info.audio_source_info.audio_buffer = subsampled;
 			data_source_info.audio_source_info.audio_buffer_length = (PDM_BUF_SIZE/DECIMATION)*2; //sizeof(subsampled);
 			err_code = app_sched_event_put(&data_source_info, sizeof(data_source_info), sd_write);
@@ -101,8 +104,19 @@ static void drv_audio_pdm_event_handler(nrfx_pdm_evt_t const * const p_evt)
 			{
 				pdm_buf[l].released = true;
 				data_source_info.audio_source_info.audio_buffer = &pdm_buf[l].mic_buf;
+				if (l == 0 && timestamp_buffer[l] == 0) {
+					// First buffer, set timestamp to recording start timestamp
+					timestamp_buffer[l] = recording_start_timestamp;
+				} else {
+					// Subsequent buffers
+					// t_rec_i = t_release_i - (PDM_BUF_SIZE / effective_sampling_rate) * 1000
+					const uint32_t base_sample_rate = 20000; // 20kHz
+					uint64_t current_time = systick_get_millis();
+					uint32_t buffer_duration = (PDM_BUF_SIZE / base_sample_rate) * 1000;
+					timestamp_buffer[l] = current_time - buffer_duration;
+				}				
 				NRF_LOG_INFO("pdm buf %d", pdm_buf[l].mic_buf[0]);
-				process_audio_buffer();
+				process_audio_buffer(l);
 				break;
 			}
 		}
@@ -123,9 +137,11 @@ static void drv_audio_pdm_event_handler(nrfx_pdm_evt_t const * const p_evt)
 	}
 }
 
-ret_code_t drv_audio_init(nrf_pdm_mode_t mode)
+ret_code_t drv_audio_init(nrf_pdm_mode_t mode, uint64_t timestamp)
 {
 
+	recording_start_timestamp = timestamp;
+
 	switch (mode)
 	{
 	case 0: //stereo
@@ -165,6 +181,7 @@ ret_code_t drv_audio_init(nrf_pdm_mode_t mode)
 	//! position. The HW in the uC is designed for this frequency but Nordic 
 	//! does not support it oficially as it's not considered tested enough 
 	//! https://devzone.nordicsemi.com/f/nordic-q-a/15150/single-pdm-microphone-at-higher-pcm-sampling-rate
+	//! NOTE: Change the clock frequency in the `drv_audio_pdm_event_handler` function if this is changed.
 	pdm_cfg.clock_freq	= 0x0A000000UL; 
 	local_freq      = pdm_cfg.clock_freq;
 

microphone/drv_audio_pdm.h

@@ -28,6 +28,6 @@ int8_t drv_audio_get_gain_l(void);
 int8_t drv_audio_get_gain_r(void);
 int16_t drv_audio_get_pdm_freq(void);
 
-ret_code_t drv_audio_init(nrf_pdm_mode_t mode);
+ret_code_t drv_audio_init(nrf_pdm_mode_t mode, uint64_t timestamp);
 
 #endif /* __DRV_AUDIO_PDM_H__ */

rythmbadge/request_handler_lib.c

@@ -230,6 +230,7 @@ static ret_code_t receive_notification_fifo_peek(receive_notification_t* receive
 	}
 
 	uint8_t tmp[notification_size];
+	memset(tmp, 0, sizeof(tmp));
 	for(uint32_t i = 0; i < notification_size; i++) {
 		app_fifo_peek(&receive_notification_fifo, i + index*notification_size, &(tmp[i]));
 	}

rythmbadge/sampling_lib.c

@@ -17,6 +17,7 @@
 #include "led.h"
 
 static sampling_configuration_t sampling_configuration;
+extern uint64_t timestamp_buffer[PDM_BUF_NUM];
 
 ret_code_t sampling_init(void)
 {
@@ -104,7 +105,10 @@ ret_code_t sampling_start_microphone(nrf_pdm_mode_t mode)
 	if (audio_switch_get_position()==OFF)
 		return ret;
 
-	ret = drv_audio_init(mode);
+	memset(timestamp_buffer, 0, sizeof(timestamp_buffer));
+	uint64_t initial_recording_timestamp = systick_get_millis();
+
+	ret = drv_audio_init(mode, initial_recording_timestamp);
 	if(ret != NRF_SUCCESS) return ret;
 
 	ret = storage_open_file(AUDIO);

sd_card/storage.c

@@ -38,9 +38,10 @@ FATFS fs;
 DIR dir;
 FILINFO fno;
 FIL audio_file_handle;
+FIL audio_metadata_file_handle;
 FIL imu_file_handle[MAX_IMU_SOURCES];
 FIL scanner_file_handle;
-
+extern uint64_t timestamp_buffer[PDM_BUF_NUM];
 
 void sd_write(void * p_event_data, uint16_t event_size)
 {
@@ -56,6 +57,20 @@ void sd_write(void * p_event_data, uint16_t event_size)
 		{
 			NRF_LOG_INFO("Audio write to sd failed: %d", ff_result);
 		}
+
+	if (!audio_metadata_file_handle.err)
+	{
+		audio_metadata_t audio_metadata_record;
+		audio_metadata_record.timestamp = timestamp_buffer[data_source_info.audio_source_info.buffer_index];
+
+		ff_result = f_write(&audio_metadata_file_handle, &audio_metadata_record, sizeof(audio_metadata_t), NULL);
+		if (ff_result != FR_OK)
+		{
+			NRF_LOG_INFO("Audio timestamp write to sd failed: %d", ff_result);
+		}
+	}
+
+
 		app_timer_stop(f_write_timeout_timer);
 	}
 	else if (data_source_info.data_source == IMU && !imu_file_handle[data_source_info.imu_source_info.imu_source].err)
@@ -102,6 +117,8 @@ static void f_sync_timeout_handler(void* p_context)
 	}
 	if (!audio_file_handle.err)
 		ff_result |= f_sync(&audio_file_handle);
+  if (!audio_metadata_file_handle.err)
+    ff_result |= f_sync(&audio_metadata_file_handle);
 	if (!scanner_file_handle.err)
 		ff_result |= f_sync(&scanner_file_handle);
 
@@ -123,6 +140,14 @@ uint32_t storage_close_file(data_source_t source)
 			NRF_LOG_INFO("close audio file error: %d", ff_result);
 			return -1;
 		}
+
+	audio_metadata_file_handle.err = 1;
+    ff_result = f_close(&audio_metadata_file_handle);
+    if (ff_result)
+    {
+      NRF_LOG_INFO("close audio timestamp file error: %d", ff_result);
+      return -1;
+    }
 	}
 	if (source == IMU)
 	{
@@ -288,6 +313,7 @@ uint32_t storage_init(void)
 	for (uint8_t sensor=0; sensor<MAX_IMU_SOURCES; sensor++)
 		imu_file_handle[sensor].err = 1;
 	audio_file_handle.err = 1;
+	audio_metadata_file_handle.err = 1;
 	scanner_file_handle.err = 1;
 	// Create the f_sync repeated timer
 	ret = app_timer_create(&f_sync_timer, APP_TIMER_MODE_REPEATED, f_sync_timeout_handler);
@@ -333,6 +359,7 @@ uint32_t storage_open_file(data_source_t source)
 	uint64_t millis = systick_get_millis();
 	uint32_t seconds = millis/1000;
 	TCHAR filename[50] = {};
+	TCHAR metadata_filename[55] = {};
 	NRF_LOG_INFO("SD: seconds: %ld", seconds);
 	NRF_LOG_INFO("SD: source: %d", source);
 	if (source == AUDIO)
@@ -366,6 +393,16 @@ uint32_t storage_open_file(data_source_t source)
 	        return -1;
 	    }
 		audio_file_handle.err = 0;
+
+	sprintf(metadata_filename, "%s.d", filename);
+	ff_result = f_open(&audio_metadata_file_handle, metadata_filename, FA_WRITE | FA_CREATE_ALWAYS);
+	NRF_LOG_INFO("SD Audio Metadata: ff_result: %d", ff_result);
+	if (ff_result != FR_OK)
+	{
+		NRF_LOG_INFO("SD Audio Metadata: Unable to open or create file: %d", metadata_filename);
+		return -1;
+	}
+	audio_metadata_file_handle.err = 0;
 	}
 	if (source == IMU)
 	{

sd_card/storage.h

@@ -31,10 +31,15 @@ typedef struct {
 } imu_source_info_t;
 
 typedef struct {
+	uint8_t buffer_index;
 	uint16_t audio_buffer_length;
 	const void * audio_buffer;
 } audio_source_info_t;
 
+typedef struct __attribute__((__packed__)) {
+	uint64_t timestamp;
+} audio_metadata_t;
+
 typedef struct __attribute__((__packed__)) {
 	data_source_t data_source;
 	union{