timer: add timer to force end stream

Add a timer that sends MSG_STOP N seconds after starting, where N is the
value of CONFIG_WILLOW_STREAM_TIMEOUT.

We don't need this for the following case, audio_rec_cfg_t.wakeup_time
already takes care of it:

I (00:16:15.053) WILLOW: AUDIO_REC_WAKEUP_START

I (00:16:25.053) WILLOW: AUDIO_REC_WAKEUP_END

Default to 5s which should be long enough for most commands. And max
timeout 30s which matches Whisper's default max without chunking.

Closes #18.

main/Kconfig.projbuild

@@ -200,6 +200,13 @@ config WILLOW_RECORD_BUFFER
     help
         Custom record buffer for timing and latency
 
+config WILLOW_STREAM_TIMEOUT
+    int "Maximum stream duration"
+    range 1 30
+    default 5
+    help
+        Stop stream N seconds after wake event to avoid endless stream when VAD END doesn't trigger.
+
 config WILLOW_DEBUG_MEM
     bool "Debug Willow memory"
     help

main/main.c

@@ -57,7 +57,8 @@
 
 #define I2S_PORT I2S_NUM_0
 
-static bool recording = false;
+bool recording = false;
+
 static bool stream_to_api = false;
 static int total_write = 0;
 
@@ -118,6 +119,9 @@ static esp_err_t cb_ar_event(audio_rec_evt_t are, void *data)
     switch (are) {
         case AUDIO_REC_VAD_END:
             ESP_LOGI(TAG, "AUDIO_REC_VAD_END");
+            if (esp_timer_is_active(hdl_sess_timer)) {
+                esp_timer_stop(hdl_sess_timer);
+            }
             break;
         case AUDIO_REC_VAD_START:
             ESP_LOGI(TAG, "AUDIO_REC_VAD_START");
@@ -127,6 +131,10 @@ static esp_err_t cb_ar_event(audio_rec_evt_t are, void *data)
             msg = MSG_START;
 #endif
             xQueueSend(q_rec, &msg, 0);
+            if (esp_timer_is_active(hdl_sess_timer)) {
+                esp_timer_stop(hdl_sess_timer);
+            }
+            esp_timer_start_once(hdl_sess_timer, CONFIG_WILLOW_STREAM_TIMEOUT * 1000 * 1000);
             break;
         case AUDIO_REC_COMMAND_DECT:
             // Multinet timeout
@@ -808,6 +816,7 @@ void app_main(void)
     init_buttons();
     init_input_key_service();
     init_lvgl_touch();
+    init_session_timer();
     init_timer();
     init_ap_to_api();
     start_rec();

main/shared.h

@@ -2,6 +2,8 @@
 
 #define WAKENET_NAME "wn9_alexa"
 
+bool recording;
+
 esp_periph_set_handle_t hdl_pset;
 
 extern QueueHandle_t q_rec;

main/timer.c

@@ -1,15 +1,27 @@
 #include "driver/timer.h"
+#include "esp_log.h"
 #include "freertos/FreeRTOS.h"
 #include "freertos/queue.h"
 
+#include "shared.h"
 #include "tasks.h"
 #include "timer.h"
 
 #define TIMER_DIV   (16)
 #define TIMER_SCALE (TIMER_BASE_CLK / TIMER_DIV)
 
+esp_timer_handle_t hdl_sess_timer = NULL;
 xQueueHandle hdl_q_timer = NULL;
 
+static void cb_session_timer(void *data)
+{
+    if (recording) {
+        ESP_LOGI(TAG, "session timer expired - forcing end stream");
+        int msg = MSG_STOP;
+        xQueueSend(q_rec, &msg, 0);
+    }
+}
+
 static bool IRAM_ATTR cb_timer_isr(void *data)
 {
     BaseType_t hiprio_woken = pdFALSE;
@@ -45,4 +57,14 @@ void reset_timer(bool pause)
         timer_pause(TIMER_GROUP_0, TIMER_0);
     }
     timer_set_counter_value(TIMER_GROUP_0, TIMER_0, 0);
+}
+
+esp_err_t init_session_timer(void)
+{
+    const esp_timer_create_args_t cfg_et = {
+        .callback = &cb_session_timer,
+        .name = "session_timer",
+    };
+
+    return esp_timer_create(&cfg_et, &hdl_sess_timer);
 }

main/timer.h

@@ -1,4 +1,6 @@
+esp_timer_handle_t hdl_sess_timer;
 xQueueHandle hdl_q_timer;
 
+esp_err_t init_session_timer(void);
 void init_timer(void);
 void reset_timer(bool pause);