Attempt to reduce audio crackle when sending interrupts.

Gadgetoid · Apr 9, 2024 · 459fa61 · 459fa61
1 parent 048d9c0
commit 459fa61
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Showing 3 changed files with 41 additions and 31 deletions.
diff --git a/src/board.cpp b/src/board.cpp
@@ -7,6 +7,7 @@
 #include "hardware/structs/rosc.h"
 #include "hardware/watchdog.h"
 #include "hardware/sync.h"
+#include "hardware/vreg.h"
 
 using namespace encoder;
 using namespace pimoroni;
@@ -20,6 +21,12 @@ absolute_time_t pressed_time;
 
 extern "C" {
     void system_init() {
+        // Apply a modest overvolt, default is 1.10v.
+        // this is required for a stable 250MHz on some RP2040s
+        vreg_set_voltage(VREG_VOLTAGE_1_20);
+        sleep_ms(10);
+        set_sys_clock_khz(250000, true);
+
         // DCDC PSM control
         // 0: PFM mode (best efficiency)
         // 1: PWM mode (improved ripple)

diff --git a/src/main.c b/src/main.c
@@ -435,7 +435,35 @@ bool tud_audio_tx_done_pre_load_cb(uint8_t rhport, uint8_t itf, uint8_t ep_in, u
 void audio_task(void)
 {
   static uint32_t start_ms = 0;
-  uint32_t volume_interval_ms = 10;
+  uint32_t volume_interval_ms = 50;
+
+  // When new data arrived, copy data from speaker buffer, to microphone buffer
+  // and send it over
+  // Only support speaker & headphone both have the same resolution
+  // If one is 16bit another is 24bit be care of LOUD noise !
+  if (spk_data_size)
+  {
+    //led_b_state = !led_b_state;
+    //gpio_put(LED_B, led_b_state);
+
+    // "Hardware" volume is 0 - 100 in steps of 256, with a maximum value of 25600
+
+    //unsigned int current_volume = (unsigned int)volume[0] * volume_ramp[(uint8_t)system_volume] / 25600;
+
+    /*int current_volume = volume[0] / 100;
+    if (current_volume > 256) current_volume = 256;
+    if (current_volume < 0) current_volume = 0;
+    current_volume = volume_ramp[current_volume];*/
+
+    int current_volume = volume_ramp[system_volume];
+
+    if (mute[0]) {
+      current_volume = 0;
+    }
+
+    i2s_audio_give_buffer(spk_buf, (size_t)spk_data_size, current_resolution, current_volume);
+    spk_data_size = 0;
+  }
 
   if (board_millis() - start_ms >= volume_interval_ms)
   {
@@ -460,6 +488,7 @@ void audio_task(void)
       };
 
       tud_audio_int_write(&data);
+      tud_task();
     }
     /*if(volume_delta > 0) {
       system_led(0, 255, 0);
@@ -471,6 +500,8 @@ void audio_task(void)
 
     volume_delta *= volume_speed;
 
+    int old_system_volume = system_volume;
+
     if(volume_delta + system_volume > 255) {
         system_volume = 255;
     } else if (volume_delta + system_volume < 0) {
@@ -487,7 +518,7 @@ void audio_task(void)
     }
     */
 
-    if(volume_delta != 0) {
+    if(system_volume != old_system_volume) {
       system_led(0, system_volume, 0);
 
       volume[0] = system_volume * 100;
@@ -509,34 +540,6 @@ void audio_task(void)
 
     start_ms += volume_interval_ms;
   }
-
-  // When new data arrived, copy data from speaker buffer, to microphone buffer
-  // and send it over
-  // Only support speaker & headphone both have the same resolution
-  // If one is 16bit another is 24bit be care of LOUD noise !
-  if (spk_data_size)
-  {
-    //led_b_state = !led_b_state;
-    //gpio_put(LED_B, led_b_state);
-
-    // "Hardware" volume is 0 - 100 in steps of 256, with a maximum value of 25600
-
-    //unsigned int current_volume = (unsigned int)volume[0] * volume_ramp[(uint8_t)system_volume] / 25600;
-
-    /*int current_volume = volume[0] / 100;
-    if (current_volume > 256) current_volume = 256;
-    if (current_volume < 0) current_volume = 0;
-    current_volume = volume_ramp[current_volume];*/
-
-    int current_volume = volume_ramp[system_volume];
-
-    if (mute[0]) {
-      current_volume = 0;
-    }
-
-    i2s_audio_give_buffer(spk_buf, (size_t)spk_data_size, current_resolution, current_volume);
-    spk_data_size = 0;
-  }
 }
 
 //--------------------------------------------------------------------+

diff --git a/src/usb_descriptors.h b/src/usb_descriptors.h
@@ -82,7 +82,7 @@ enum
     /* Output Terminal Descriptor(4.7.2.5) */\
     TUD_AUDIO_DESC_OUTPUT_TERM(/*_termid*/ UAC2_ENTITY_SPK_OUTPUT_TERMINAL, /*_termtype*/ AUDIO_TERM_TYPE_OUT_GENERIC_SPEAKER, /*_assocTerm*/ 0x00, /*_srcid*/ UAC2_ENTITY_SPK_FEATURE_UNIT, /*_clkid*/ UAC2_ENTITY_CLOCK, /*_ctrl*/ 0x0000, /*_stridx*/ 0x00),\
     /* Standard AC Interrupt Endpoint Descriptor(4.8.2.1) */\
-    TUD_AUDIO_DESC_STD_AC_INT_EP(/*_ep*/ _epint, /*_interval*/ 0x01), \
+    TUD_AUDIO_DESC_STD_AC_INT_EP(/*_ep*/ _epint, /*_interval*/ 0x010), \
     /* Standard AS Interface Descriptor(4.9.1) */\
     /* Interface 1, Alternate 0 - default alternate setting with 0 bandwidth */\
     TUD_AUDIO_DESC_STD_AS_INT(/*_itfnum*/ (uint8_t)(ITF_NUM_AUDIO_STREAMING_SPK), /*_altset*/ 0x00, /*_nEPs*/ 0x00, /*_stridx*/ 0x05),\