Adjusted Oratory's default EQ:

- Less bass. Excursion limits happen at 30-50Hz first, so reducing response in this range makes it a little less likely this will be a problem. Plus, I like it.
- A little more response above 12kHz.

Updated config version to 4.

Added a parameter for post EQ gain. Applied once after EQ is calculated.

firmware/code/configuration_manager.c

@@ -54,7 +54,7 @@ static const default_configuration default_config = {
         .filter = { FILTER_CONFIGURATION, sizeof(default_config.filters) },
         .f1  = { PEAKING,    {0},    38.5, -21.0,  1.4  },
         .f2  = { PEAKING,    {0},    60,    -6.7,  0.5  },
-        .f3  = { LOWSHELF,   {0},    105,    5.5,  0.71 },
+        .f3  = { LOWSHELF,   {0},    105,    2.0,  0.71 },
         .f4  = { PEAKING,    {0},    280,   -3.5,  1.1  },
         .f5  = { PEAKING,    {0},    350,   -1.6,  6.0  },
         .f6  = { PEAKING,    {0},    425,    7.8,  1.3  },
@@ -66,9 +66,15 @@ static const default_configuration default_config = {
         .f12 = { PEAKING,    {0},   3430,  -12.2,  2.0  },
         .f13 = { PEAKING,    {0},   4800,    4.0,  2.0  },
         .f14 = { PEAKING,    {0},   6200,  -15.0,  3.0  },
-        .f15 = { HIGHSHELF,  {0},  12000,   -6.0,  0.71 }
+        .f15 = { HIGHSHELF,  {0},  12000,   -3.0,  0.71 }
     },
-    .preprocessing = { .header = { PREPROCESSING_CONFIGURATION, sizeof(default_config.preprocessing) }, -0.08f, true, {0} }
+    .preprocessing = { 
+        .header = { PREPROCESSING_CONFIGURATION, sizeof(default_config.preprocessing) }, 
+        -0.376265f,      // pre-EQ gain of -4.1dB
+        0.4125f,       // post-EQ gain, set to ~3dB (1.4x, less the 1 that is added when config is applied)
+        true, 
+        {0} 
+    }
 };
 
 // Grab the last 4k page of flash for our configuration strutures.
@@ -316,6 +322,7 @@ bool apply_configuration(tlv_header *config) {
             case PREPROCESSING_CONFIGURATION: {
                 preprocessing_configuration_tlv* preprocessing_config = (preprocessing_configuration_tlv*) tlv;
                 preprocessing.preamp = fix3_28_from_flt(1.0f + preprocessing_config->preamp);
+                preprocessing.postEQGain = fix3_28_from_flt(1.0f + preprocessing_config->postEQGain);
                 preprocessing.reverse_stereo = preprocessing_config->reverse_stereo;
                 break;
             }
@@ -351,11 +358,13 @@ void load_config() {
 
 #ifndef TEST_TARGET
 bool __no_inline_not_in_flash_func(save_configuration)() {
+
+
+
     const uint8_t active_configuration = inactive_working_configuration ? 0 : 1;
     tlv_header* config = (tlv_header*) working_configuration[active_configuration];
 
-    if (validate_configuration(config)) {
-        power_down_dac();
+    if (validate_configuration(config)) {      
 
         const size_t config_length = config->length - ((size_t)config->value - (size_t)config);
         // Write data to flash
@@ -367,6 +376,10 @@ bool __no_inline_not_in_flash_func(save_configuration)() {
         flash_header->version = CONFIG_VERSION;
         memcpy((void*)(flash_header->tlvs), config->value, config_length);
 
+        /* Turn the DAC off so we don't make a huge noise when disrupting
+           real time audio operation. */
+        power_down_dac();
+
         uint32_t ints = save_and_disable_interrupts();
         flash_range_erase(USER_CONFIGURATION_OFFSET, FLASH_SECTOR_SIZE);
         flash_range_program(USER_CONFIGURATION_OFFSET, flash_buffer, CFG_BUFFER_SIZE);
@@ -376,6 +389,7 @@ bool __no_inline_not_in_flash_func(save_configuration)() {
 
         return true;
     }
+
     return false;
 }
 

firmware/code/configuration_types.h

@@ -17,8 +17,8 @@
 #include <stdint.h>
 
 #define FLASH_MAGIC 0x2E8AFEDD
-#define CONFIG_VERSION 3
-#define MINIMUM_CONFIG_VERSION 3
+#define CONFIG_VERSION 4
+#define MINIMUM_CONFIG_VERSION 4
 
 enum structure_types {
     // Commands/Responses, these are container TLVs. The Value will be a set of TLV structures.
@@ -98,9 +98,13 @@ typedef struct __attribute__((__packed__)) _flash_header_tlv {
     const uint8_t tlvs[0];
 } flash_header_tlv;
 
+/// @brief Holds values relating to processing surrounding the EQ calculation.
 typedef struct __attribute__((__packed__)) _preprocessing_configuration_tlv {
     tlv_header header;
+    /// @brief Gain applied to input signal before EQ chain. Use to avoid clipping due to overflow in the biquad filters of the EQ.
     float preamp;
+    /// @brief Gain applied to the output of the EQ chain. Used to set output volume.
+    float postEQGain;
     uint8_t reverse_stereo;
     uint8_t reserved[3];
 } preprocessing_configuration_tlv;

firmware/code/run.c

@@ -56,6 +56,7 @@ audio_state_config audio_state = {
 
 preprocessing_config preprocessing = {
     .preamp = fix16_one,
+    .postEQGain = fix16_one,
     .reverse_stereo = false
 };
 
@@ -148,6 +149,10 @@ static void __no_inline_not_in_flash_func(_as_audio_packet)(struct usb_endpoint
             x_f16 = bqf_transform(x_f16, &bqf_filters_left[j],
                 &bqf_filters_mem_left[j]);
         }
+
+        /* Apply post-EQ gain. */
+        x_f16 = fix16_mul( x_f16, preprocessing.postEQGain);
+
         out[i] = (int32_t) norm_fix3_28_to_s16sample(x_f16);
     }
 
@@ -186,12 +191,18 @@ void __no_inline_not_in_flash_func(core1_entry)() {
 
         const uint32_t samples = multicore_fifo_pop_blocking();
 
+        /* Right channel EQ. */
         for (int i = 1; i < samples; i += 2) {
+            /* Apply EQ pre-filter gain to avoid clipping. */
             fix3_28_t x_f16 = fix16_mul(norm_fix3_28_from_s16sample((int16_t) out[i]), preprocessing.preamp);
+            /* Apply the biquad filters one by one. */
             for (int j = 0; j < filter_stages; j++) {
                 x_f16 = bqf_transform(x_f16, &bqf_filters_right[j],
                     &bqf_filters_mem_right[j]);
             }
+            /* Apply post-EQ gain. */
+            x_f16 = fix16_mul( x_f16, preprocessing.postEQGain);
+
             out[i] = (int32_t) norm_fix3_28_to_s16sample(x_f16);
         }
 
@@ -957,7 +968,7 @@ void power_down_dac() {
     i2c_write_blocking(i2c0, PCM_I2C_ADDR, buf, 2, false);
 }
 
-void power_up_dac() {
+void power_up_dac() {    
     uint8_t buf[2];
     buf[0] = 64; // register addr
     buf[1] = 0xE0; // DAC normal mode

firmware/code/run.h

@@ -110,6 +110,8 @@ typedef struct _audio_device_config {
 
 typedef struct _preprocessing_config {
     fix3_28_t preamp;
+    /// @brief Apply this gain after applying EQ, to set output volume without causing overflow in the EQ calculations.
+    fix3_28_t postEQGain;
     int reverse_stereo;
 } preprocessing_config;