Rollback changes we dont need.

firmware/code/configuration_manager.c

@@ -53,8 +53,8 @@ static const default_configuration default_config = {
     .filters = {
         .filter = { FILTER_CONFIGURATION, sizeof(default_config.filters) },
         .f1  = { PEAKING,    {0},    38.5, -21.0,  1.4  },
-        .f2  = { LOWSHELF,   {0},    60,    -6.7,  0.5  },
-        .f3  = { PEAKING,    {0},    105,    5.5,  0.71 },
+        .f2  = { PEAKING,    {0},    60,    -6.7,  0.5  },
+        .f3  = { LOWSHELF,   {0},    105,    5.5,  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  },
@@ -68,7 +68,7 @@ static const default_configuration default_config = {
         .f14 = { PEAKING,    {0},   6200,  -15.0,  3.0  },
         .f15 = { HIGHSHELF,  {0},  12000,   -6.0,  0.71 }
     },
-    .preprocessing = { .header = { PREPROCESSING_CONFIGURATION, sizeof(default_config.preprocessing) }, -0.16f, true, {0} }
+    .preprocessing = { .header = { PREPROCESSING_CONFIGURATION, sizeof(default_config.preprocessing) }, -0.06f, true, {0} }
 };
 
 // Grab the last 4k page of flash for our configuration strutures.

firmware/code/i2s.c

@@ -64,7 +64,7 @@ void i2s_write_init(i2s_obj_t *self) {
             self->prog_offset + self->pio_program->length - 1);
     pio_sm_set_config(self->pio, self->sm, &config);
 
-    uint32_t *rbs = malloc(sizeof(uint8_t) * RINGBUF_LEN_IN_BYTES);
+    uint8_t *rbs = malloc(sizeof(uint8_t) * RINGBUF_LEN_IN_BYTES);
     ringbuf_init(&self->ring_buffer, rbs, RINGBUF_LEN_IN_BYTES);
 
     irq_set_exclusive_handler(DMA_IRQ_1, dma_irq_write_handler);
@@ -169,27 +169,27 @@ uint8_t *dma_get_buffer(i2s_obj_t *i2s_obj, uint channel) {
 void feed_dma(i2s_obj_t *self, uint8_t *dma_buffer_p) {
     // when data exists, copy samples from ring buffer
     if (ringbuf_available_data(&self->ring_buffer) >= SIZEOF_HALF_DMA_BUFFER_IN_BYTES) {
-        for (uint32_t i = 0; i < SIZEOF_HALF_DMA_BUFFER_IN_BYTES; i+=4)
-            ringbuf_pop(&self->ring_buffer, (uint32_t*)&dma_buffer_p[i]);
+        for (uint32_t i = 0; i < SIZEOF_HALF_DMA_BUFFER_IN_BYTES; i++)
+            ringbuf_pop(&self->ring_buffer, &dma_buffer_p[i]);
     } else {
         // underflow.  clear buffer to transmit "silence" on the I2S bus
         memset(dma_buffer_p, 0, SIZEOF_HALF_DMA_BUFFER_IN_BYTES);
     }
 }
 
-uint i2s_stream_write(i2s_obj_t *self, const uint32_t *buf_out, uint size) {
+uint i2s_stream_write(i2s_obj_t *self, const uint8_t *buf_out, uint size) {
     if (size == 0) {
         //printf("ERROR: buffer can't be length zero");
         exit(1);
     }
 
-    uint32_t num_words_written = copy_userbuf_to_ringbuf(self, buf_out, size);
-    return num_words_written;
+    uint32_t num_bytes_written = copy_userbuf_to_ringbuf(self, buf_out, size);
+    return num_bytes_written;
 }
 
 // TODO maybe we can skip every fourth byte, if we're doing this in 24-bit...
 // could save on some processing power
-uint32_t copy_userbuf_to_ringbuf(i2s_obj_t *self, const uint32_t *buf_out, uint size) {
+uint32_t copy_userbuf_to_ringbuf(i2s_obj_t *self, const uint8_t *buf_out, uint size) {
     uint32_t a_index = 0;
 
     while (a_index < size) {

firmware/code/i2s.h

@@ -59,7 +59,7 @@ typedef struct _i2s_obj_t {
 extern i2s_obj_t i2s_write_obj;
 
 void i2s_write_init(i2s_obj_t *);
-uint i2s_stream_write(i2s_obj_t *, const uint32_t *, uint);
+uint i2s_stream_write(i2s_obj_t *, const uint8_t *, uint);
 
 void dma_irq_handler(uint8_t);
 void dma_irq_write_handler(void);
@@ -68,6 +68,6 @@ void dma_configure(i2s_obj_t *);
 uint8_t *dma_get_buffer(i2s_obj_t *, uint);
 void feed_dma(i2s_obj_t *, uint8_t *);
 
-uint32_t copy_userbuf_to_ringbuf(i2s_obj_t *, const uint32_t *, uint);
+uint32_t copy_userbuf_to_ringbuf(i2s_obj_t *, const uint8_t *, uint);
 
-#endif
+#endif

firmware/code/ringbuf.c

@@ -33,14 +33,14 @@
 // - Sequential atomic operations
 // One byte of capacity is used to detect buffer empty/full
 
-void ringbuf_init(ring_buf_t *rbuf, uint32_t *buffer, size_t size) {
+void ringbuf_init(ring_buf_t *rbuf, uint8_t *buffer, size_t size) {
     rbuf->buffer = buffer;
     rbuf->size = size;
     rbuf->head = 0;
     rbuf->tail = 0;
 }
 
-bool ringbuf_push(ring_buf_t *rbuf, uint32_t data) {
+bool ringbuf_push(ring_buf_t *rbuf, uint8_t data) {
     size_t next_tail = (rbuf->tail + 1) % rbuf->size;
 
     if (next_tail != rbuf->head) {
@@ -53,7 +53,7 @@ bool ringbuf_push(ring_buf_t *rbuf, uint32_t data) {
     return false;
 }
 
-bool ringbuf_pop(ring_buf_t *rbuf, uint32_t *data) {
+bool ringbuf_pop(ring_buf_t *rbuf, uint8_t *data) {
     if (rbuf->head == rbuf->tail) {
         // empty
         return false;
@@ -78,4 +78,4 @@ size_t ringbuf_available_data(ring_buf_t *rbuf) {
 
 size_t ringbuf_available_space(ring_buf_t *rbuf) {
     return rbuf->size - ringbuf_available_data(rbuf) - 1;
-}
+}

firmware/code/ringbuf.h

@@ -28,18 +28,18 @@
 #include "pico/stdlib.h"
 
 typedef struct _ring_buf_t {
-    uint32_t *buffer;
+    uint8_t *buffer;
     size_t head;
     size_t tail;
     size_t size;
 } ring_buf_t;
 
-void ringbuf_init(ring_buf_t *, uint32_t *, size_t);
-bool ringbuf_push(ring_buf_t *, uint32_t );
-bool ringbuf_pop(ring_buf_t *, uint32_t *);
+void ringbuf_init(ring_buf_t *, uint8_t *, size_t);
+bool ringbuf_push(ring_buf_t *, uint8_t );
+bool ringbuf_pop(ring_buf_t *, uint8_t *);
 bool ringbuf_is_empty(ring_buf_t *);
 bool ringbuf_is_full(ring_buf_t *);
 size_t ringbuf_available_data(ring_buf_t *);
 size_t ringbuf_available_space(ring_buf_t *);
 
-#endif
+#endif

firmware/code/run.c

@@ -124,63 +124,90 @@ static void __no_inline_not_in_flash_func(_as_audio_packet)(struct usb_endpoint
     int32_t *out = (int32_t *) userbuf;
     int samples = usb_buffer->data_len / 2;
 
-    const fix3_28_t preamp = preprocessing.preamp;
-    for (int i = 0; i < samples; i ++) {
-        out[i] = fix16_mul(norm_fix3_28_from_s16sample(in[i]), preamp);
-    }
-
-    // keep on truckin'
-    usb_grow_transfer(ep->current_transfer, 1);
-    usb_packet_done(ep);
-
-    multicore_fifo_push_blocking(samples);
     if (preprocessing.reverse_stereo) {
-        multicore_fifo_push_blocking((uintptr_t) (out - 1));
-        out ++;
+        for (int i = 0; i < samples; i+=2) {
+            out[i] = in[i+1];
+            out[i+1] = in[i];
+        }
     }
     else {
-        multicore_fifo_push_blocking((uintptr_t) out);
+        for (int i = 0; i < samples; i++)
+            out[i] = in[i];
     }
+
+    // Make sure core 1 is ready for us.
+    multicore_fifo_pop_blocking();
+    multicore_fifo_push_blocking(CORE0_READY);
+    multicore_fifo_push_blocking(samples);
 
-    for (int i = 0; i < samples; i += 2) {
-        for (int j = 0; j < filter_stages; j++) {
-            out[i] = bqf_transform(out[i], &bqf_filters_left[j], &bqf_filters_mem_left[j]);
+    for (int j = 0; j < filter_stages; j++) {
+        // Left channel filter
+        for (int i = 0; i < samples; i += 2) {
+            fix3_28_t x_f16 = fix16_mul(norm_fix3_28_from_s16sample((int16_t) out[i]), preprocessing.preamp);
+
+            x_f16 = bqf_transform(x_f16, &bqf_filters_left[j],
+                &bqf_filters_mem_left[j]);
+
+            out[i] = (int32_t) norm_fix3_28_to_s16sample(x_f16);
         }
-        out[i] = (int32_t) norm_fix3_28_to_s16sample(out[i]);
     }
 
-    // Signal to core 1 that we have processed our samples, so it can write to I2S
+    // Block until core 1 has finished transforming the data
+    uint32_t ready = multicore_fifo_pop_blocking();
     multicore_fifo_push_blocking(CORE0_READY);
 
+    // Update the volume if required. We do this from core1 as
+    // core0 is more heavily loaded, doing this from core0 can
+    // lead to audio crackling.
     update_volume();
+
+    // Update filters if required
     apply_config_changes();
+
+    // keep on truckin'
+    usb_grow_transfer(ep->current_transfer, 1);
+    usb_packet_done(ep);
 }
 
 void __no_inline_not_in_flash_func(core1_entry)() {
-    uint32_t *userbuf = (uint32_t *) multicore_fifo_pop_blocking();
+    uint8_t *userbuf = (uint8_t *) multicore_fifo_pop_blocking();
+    int32_t *out = (int32_t *) userbuf;
 
     // Signal that the thread has started
     multicore_fifo_push_blocking(CORE1_READY);
 
     while (true) {
+        // Signal to core 0 that we are ready to accept new data
+        multicore_fifo_push_blocking(CORE1_READY);
+
+        // Block until the userbuf is filled with data
+        uint32_t ready = multicore_fifo_pop_blocking();
+        while (ready != CORE0_READY)
+            ready = multicore_fifo_pop_blocking();
+
         const uint32_t samples = multicore_fifo_pop_blocking();
-        int32_t *out = (int32_t *) multicore_fifo_pop_blocking();
 
-        for (int i = 1; i < samples; i += 2) {
-            for (int j = 0; j < filter_stages; j++) {
-                out[i] = bqf_transform(out[i], &bqf_filters_right[j], &bqf_filters_mem_right[j]);
+        for (int j = 0; j < filter_stages; j++) {
+            for (int i = 1; i < samples; i += 2) {
+                fix3_28_t x_f16 = fix16_mul(norm_fix3_28_from_s16sample((int16_t) out[i]), preprocessing.preamp);
+
+                x_f16 = bqf_transform(x_f16, &bqf_filters_right[j],
+                    &bqf_filters_mem_right[j]);
+
+                out[i] = (int16_t) norm_fix3_28_to_s16sample(x_f16);
             }
-            out[i] = (int32_t) norm_fix3_28_to_s16sample(out[i]);
         }
 
+        // Signal to core 0 that the data has all been transformed
+        multicore_fifo_push_blocking(CORE1_READY);
+
         // Wait for Core 0 to finish running its filtering before we apply config updates
         multicore_fifo_pop_blocking();
-        i2s_stream_write(&i2s_write_obj, userbuf, samples);
+
+        i2s_stream_write(&i2s_write_obj, userbuf, samples * 4);
     }
 }
 
-static const audio_device_config ad_conf;
-
 void setup() {
     set_sys_clock_khz(SYSTEM_FREQ / 1000, true);
     sleep_ms(100);