Mostly working pipeline, including proper EOF signalling

19 files changed, 244 insertions, 44 deletions

diff --git a/src/audio/audio_decoder.cpp b/src/audio/audio_decoder.cpp
index 27b9cca3..d90ca496 100644
--- a/src/audio/audio_decoder.cpp
+++ b/src/audio/audio_decoder.cpp
@@ -84,6 +84,16 @@ auto AudioDecoder::ProcessChunk(const cpp::span<std::byte>& chunk)
   return {};
 }
 
+auto AudioDecoder::ProcessEndOfStream() -> void {
+  has_samples_to_send_ = false;
+  needs_more_input_ = true;
+  current_codec_.reset();
+
+  SendOrBufferEvent(
+      std::unique_ptr<StreamEvent>(
+        StreamEvent::CreateEndOfStream(input_events_)));
+}
+
 auto AudioDecoder::Process() -> cpp::result<void, AudioProcessingError> {
   if (has_samples_to_send_) {
     ESP_LOGI(kTag, "sending samples");
@@ -132,7 +142,7 @@ auto AudioDecoder::Process() -> cpp::result<void, AudioProcessingError> {
     has_samples_to_send_ = true;
 
     if (needs_more_input_) {
-      chunk_reader_->HandleLeftovers(current_codec_->GetInputPosition());
+      chunk_reader_->HandleBytesUsed(current_codec_->GetInputPosition());
     }
   }
 
diff --git a/src/audio/audio_playback.cpp b/src/audio/audio_playback.cpp
index 4df598c5..504a2a4e 100644
--- a/src/audio/audio_playback.cpp
+++ b/src/audio/audio_playback.cpp
@@ -38,9 +38,9 @@ auto AudioPlayback::create(drivers::GpioExpander* expander,
   playback->ConnectElements(codec.get(), sink.get());
 
   // Launch!
-  playback->element_handles_.push_back(StartAudioTask("src", source));
-  playback->element_handles_.push_back(StartAudioTask("dec", codec));
-  playback->element_handles_.push_back(StartAudioTask("sink", sink));
+  playback->element_handles_.push_back(StartAudioTask("src", {}, source));
+  playback->element_handles_.push_back(StartAudioTask("dec", {}, codec));
+  playback->element_handles_.push_back(StartAudioTask("sink", 0, sink));
 
   playback->input_handle_ = source->InputEventQueue();
 
@@ -60,6 +60,8 @@ auto AudioPlayback::Play(const std::string& filename) -> void {
   info.path = filename;
   auto event = StreamEvent::CreateStreamInfo(input_handle_, info);
   xQueueSend(input_handle_, &event, portMAX_DELAY);
+  event = StreamEvent::CreateEndOfStream(input_handle_);
+  xQueueSend(input_handle_, &event, portMAX_DELAY);
 }
 
 auto AudioPlayback::ConnectElements(IAudioElement* src, IAudioElement* sink)
diff --git a/src/audio/audio_task.cpp b/src/audio/audio_task.cpp
index 47b115cc..078aa461 100644
--- a/src/audio/audio_task.cpp
+++ b/src/audio/audio_task.cpp
@@ -28,6 +28,7 @@ namespace audio {
 static const char* kTag = "task";
 
 auto StartAudioTask(const std::string& name,
+                    std::optional<BaseType_t> core_id,
                     std::shared_ptr<IAudioElement> element)
     -> std::unique_ptr<AudioElementHandle> {
   auto task_handle = std::make_unique<TaskHandle_t>();
@@ -36,8 +37,13 @@ auto StartAudioTask(const std::string& name,
   AudioTaskArgs* args = new AudioTaskArgs{.element = element};
 
   ESP_LOGI(kTag, "starting audio task %s", name.c_str());
-  xTaskCreate(&AudioTaskMain, name.c_str(), element->StackSizeBytes(), args,
-              kTaskPriorityAudio, task_handle.get());
+  if (core_id) {
+    xTaskCreatePinnedToCore(&AudioTaskMain, name.c_str(), element->StackSizeBytes(), args,
+                kTaskPriorityAudio, task_handle.get(), *core_id);
+  } else {
+    xTaskCreate(&AudioTaskMain, name.c_str(), element->StackSizeBytes(), args,
+                kTaskPriorityAudio, task_handle.get());
+  }
 
   return std::make_unique<AudioElementHandle>(std::move(task_handle), element);
 }
diff --git a/src/audio/chunk.cpp b/src/audio/chunk.cpp
index 61c0dc2b..01760a84 100644
--- a/src/audio/chunk.cpp
+++ b/src/audio/chunk.cpp
@@ -41,8 +41,11 @@ auto ChunkReader::HandleNewData(cpp::span<std::byte> data)
   return last_data_in_working_buffer_;
 }
 
-auto ChunkReader::HandleLeftovers(std::size_t bytes_used) -> void {
-  leftover_bytes_ = last_data_in_working_buffer_.size() - bytes_used;
+auto ChunkReader::HandleBytesUsed(std::size_t bytes_used) -> void {
+  HandleBytesLeftOver(last_data_in_working_buffer_.size() - bytes_used);
+}
+auto ChunkReader::HandleBytesLeftOver(std::size_t bytes_left) -> void {
+  leftover_bytes_ = bytes_left;
 
   // Ensure that we don't have more than a chunk of leftever bytes. This is
   // bad, because we probably won't have enough data to store the next chunk.
@@ -55,4 +58,8 @@ auto ChunkReader::HandleLeftovers(std::size_t bytes_used) -> void {
   }
 }
 
+auto ChunkReader::GetLeftovers() -> cpp::span<std::byte> {
+  return working_buffer_.first(leftover_bytes_);
+}
+
 }  // namespace audio
diff --git a/src/audio/fatfs_audio_input.cpp b/src/audio/fatfs_audio_input.cpp
index 08f39347..8990bf4f 100644
--- a/src/audio/fatfs_audio_input.cpp
+++ b/src/audio/fatfs_audio_input.cpp
@@ -69,6 +69,16 @@ auto FatfsAudioInput::ProcessChunk(const cpp::span<std::byte>& chunk)
   return cpp::fail(UNSUPPORTED_STREAM);
 }
 
+auto FatfsAudioInput::ProcessEndOfStream() -> void {
+  if (is_file_open_) {
+      f_close(&current_file_);
+      is_file_open_ = false;
+      SendOrBufferEvent(
+          std::unique_ptr<StreamEvent>(
+            StreamEvent::CreateEndOfStream(input_events_)));
+  }
+}
+
 auto FatfsAudioInput::Process() -> cpp::result<void, AudioProcessingError> {
   if (is_file_open_) {
     auto dest_event = std::unique_ptr<StreamEvent>(
diff --git a/src/audio/i2s_audio_output.cpp b/src/audio/i2s_audio_output.cpp
index b00e31d3..3bed15b5 100644
--- a/src/audio/i2s_audio_output.cpp
+++ b/src/audio/i2s_audio_output.cpp
@@ -7,6 +7,7 @@
 
 #include "audio_element.hpp"
 #include "dac.hpp"
+#include "freertos/projdefs.h"
 #include "gpio_expander.hpp"
 #include "result.hpp"
 
@@ -15,6 +16,8 @@ static const char* kTag = "I2SOUT";
 
 namespace audio {
 
+static const std::size_t kDmaQueueLength = 8;
+
 auto I2SAudioOutput::create(drivers::GpioExpander* expander)
     -> cpp::result<std::shared_ptr<I2SAudioOutput>, Error> {
   // First, we need to perform initial configuration of the DAC chip.
@@ -38,12 +41,26 @@ I2SAudioOutput::I2SAudioOutput(drivers::GpioExpander* expander,
     : expander_(expander),
       dac_(std::move(dac)),
       volume_(255),
-      is_soft_muted_(false) {}
+      is_soft_muted_(false),
+      chunk_reader_(),
+      latest_chunk_(),
+      dma_size_(),
+      dma_queue_(nullptr) {}
 
 I2SAudioOutput::~I2SAudioOutput() {
+  if (dma_queue_ != nullptr) {
+    ClearDmaQueue();
+  }
   // TODO: power down the DAC.
 }
 
+auto I2SAudioOutput::HasUnprocessedInput() -> bool {
+  if (dma_queue_ == nullptr || !dma_size_) {
+    return false;
+  }
+  return latest_chunk_.size() >= *dma_size_;
+}
+
 auto I2SAudioOutput::ProcessStreamInfo(const StreamInfo& info)
     -> cpp::result<void, AudioProcessingError> {
   // TODO(jacqueline): probs do something with the channel hey
@@ -53,6 +70,12 @@ auto I2SAudioOutput::ProcessStreamInfo(const StreamInfo& info)
     return cpp::fail(UNSUPPORTED_STREAM);
   }
 
+  if (!info.chunk_size) {
+    ESP_LOGE(kTag, "audio stream missing chunk size");
+    return cpp::fail(UNSUPPORTED_STREAM);
+  }
+  chunk_reader_.emplace(*info.chunk_size);
+
   ESP_LOGI(kTag, "incoming audio stream: %u bpp @ %u Hz", *info.bits_per_sample,
            *info.sample_rate);
 
@@ -85,23 +108,78 @@ auto I2SAudioOutput::ProcessStreamInfo(const StreamInfo& info)
       return cpp::fail(UNSUPPORTED_STREAM);
   }
 
-  dac_->Reconfigure(bps, sample_rate);
+  QueueHandle_t new_dma_queue =
+      xQueueCreate(kDmaQueueLength, sizeof(std::byte*));
+
+  dma_size_ = dac_->Reconfigure(bps, sample_rate, new_dma_queue);
+
+  if (dma_queue_ != nullptr) {
+    ClearDmaQueue();
+  }
+  dma_queue_ = new_dma_queue;
 
   return {};
 }
 
 auto I2SAudioOutput::ProcessChunk(const cpp::span<std::byte>& chunk)
     -> cpp::result<std::size_t, AudioProcessingError> {
-  ESP_LOGI(kTag, "playing samples");
-  SetSoftMute(false);
-  // TODO(jacqueline): write smaller parts with a small delay so that we can
-  // be responsive to pause and seek commands.
-  dac_->WriteData(chunk, portMAX_DELAY);
+  ESP_LOGI(kTag, "received new samples");
+  latest_chunk_ = chunk_reader_->HandleNewData(chunk);
   return 0;
 }
 
+auto I2SAudioOutput::ProcessEndOfStream() -> void {
+  if (chunk_reader_ && dma_size_) {
+    auto leftovers = chunk_reader_->GetLeftovers();
+    if (leftovers.size() > 0 && leftovers.size() < *dma_size_) {
+      std::byte* dest = static_cast<std::byte*>(malloc(*dma_size_));
+      cpp::span dest_span(dest, *dma_size_);
+
+      std::copy(leftovers.begin(), leftovers.end(), dest_span.begin());
+      std::fill(dest_span.begin() + leftovers.size(), dest_span.end(), static_cast<std::byte>(0));
+
+      xQueueSend(dma_queue_, &dest, portMAX_DELAY);
+    }
+  }
+
+  SendOrBufferEvent(
+      std::unique_ptr<StreamEvent>(
+        StreamEvent::CreateEndOfStream(input_events_)));
+
+  chunk_reader_.reset();
+  dma_size_.reset();
+}
+
 auto I2SAudioOutput::Process() -> cpp::result<void, AudioProcessingError> {
-  // TODO(jacqueline): Play the stream in smaller sections
+  std::size_t spaces_available = uxQueueSpacesAvailable(dma_queue_);
+  if (spaces_available == 0) {
+    // TODO: think about this more. can this just be the output event queue?
+    vTaskDelay(pdMS_TO_TICKS(100));
+    return {};
+  }
+
+  // Fill the queue as much as possible, since we need to be able to stream
+  // FAST.
+  while (latest_chunk_.size() >= *dma_size_ && spaces_available > 0) {
+    // TODO: small memory arena for this?
+    std::byte* dest = static_cast<std::byte*>(malloc(*dma_size_));
+    cpp::span dest_span(dest, *dma_size_);
+    cpp::span src_span = latest_chunk_.first(*dma_size_);
+    std::copy(src_span.begin(), src_span.end(), dest_span.begin());
+    if (!xQueueSend(dma_queue_, &dest, 0)) {
+      // TODO: calculate how often we expect this to happen.
+      free(dest);
+      break;
+    }
+    latest_chunk_ = latest_chunk_.subspan(*dma_size_);
+    ESP_LOGI(kTag, "wrote dma buffer of size %u", *dma_size_);
+  }
+  if (latest_chunk_.size() < *dma_size_) {
+    // TODO: if this is the end of the stream, then we should be sending this
+    // with zero padding. hmm. i guess we need an explicit EOF event?
+    chunk_reader_->HandleBytesLeftOver(latest_chunk_.size());
+    ESP_LOGI(kTag, "not enough samples for dma buffer");
+  }
   return {};
 }
 
@@ -124,4 +202,17 @@ auto I2SAudioOutput::SetSoftMute(bool enabled) -> void {
   }
 }
 
+auto I2SAudioOutput::ClearDmaQueue() -> void {
+  // Ensure we don't leak any memory from events leftover in the queue.
+  while (uxQueueSpacesAvailable(dma_queue_) < kDmaQueueLength) {
+    std::byte* data = nullptr;
+    if (xQueueReceive(input_events_, &data, 0)) {
+      free(data);
+    } else {
+      break;
+    }
+  }
+  vQueueDelete(dma_queue_);
+}
+
 }  // namespace audio
diff --git a/src/audio/include/audio_decoder.hpp b/src/audio/include/audio_decoder.hpp
index d0f7469b..aa83825f 100644
--- a/src/audio/include/audio_decoder.hpp
+++ b/src/audio/include/audio_decoder.hpp
@@ -37,6 +37,7 @@ class AudioDecoder : public IAudioElement {
       -> cpp::result<void, AudioProcessingError> override;
   auto ProcessChunk(const cpp::span<std::byte>& chunk)
       -> cpp::result<std::size_t, AudioProcessingError> override;
+  auto ProcessEndOfStream() -> void override;
   auto Process() -> cpp::result<void, AudioProcessingError> override;
 
   AudioDecoder(const AudioDecoder&) = delete;
diff --git a/src/audio/include/audio_element.hpp b/src/audio/include/audio_element.hpp
index c6453d4d..0c80524c 100644
--- a/src/audio/include/audio_element.hpp
+++ b/src/audio/include/audio_element.hpp
@@ -105,6 +105,8 @@ class IAudioElement {
   virtual auto ProcessChunk(const cpp::span<std::byte>& chunk)
       -> cpp::result<std::size_t, AudioProcessingError> = 0;
 
+  virtual auto ProcessEndOfStream() -> void = 0;
+
   /*
    * Called when there has been no data received over the input buffer for some
    * time. This could be used to synthesize output, or to save memory by
diff --git a/src/audio/include/audio_task.hpp b/src/audio/include/audio_task.hpp
index 9a76ea7e..399ad679 100644
--- a/src/audio/include/audio_task.hpp
+++ b/src/audio/include/audio_task.hpp
@@ -1,9 +1,12 @@
 #pragma once
 
 #include <memory>
+#include <string>
+#include <optional>
 
 #include "audio_element.hpp"
 #include "audio_element_handle.hpp"
+#include "freertos/portmacro.h"
 
 namespace audio {
 
@@ -12,6 +15,7 @@ struct AudioTaskArgs {
 };
 
 auto StartAudioTask(const std::string& name,
+                    std::optional<BaseType_t> core_id,
                     std::shared_ptr<IAudioElement> element)
     -> std::unique_ptr<AudioElementHandle>;
 
diff --git a/src/audio/include/chunk.hpp b/src/audio/include/chunk.hpp
index 0ece1ed6..31e1f969 100644
--- a/src/audio/include/chunk.hpp
+++ b/src/audio/include/chunk.hpp
@@ -27,7 +27,8 @@ class ChunkReader {
   explicit ChunkReader(std::size_t chunk_size);
   ~ChunkReader();
 
-  auto HandleLeftovers(std::size_t bytes_used) -> void;
+  auto HandleBytesLeftOver(std::size_t bytes_left) -> void;
+  auto HandleBytesUsed(std::size_t bytes_used) -> void;
 
   /*
    * Reads chunks of data from the given input stream, and invokes the given
@@ -43,6 +44,8 @@ class ChunkReader {
    */
   auto HandleNewData(cpp::span<std::byte> data) -> cpp::span<std::byte>;
 
+  auto GetLeftovers() -> cpp::span<std::byte>;
+
   ChunkReader(const ChunkReader&) = delete;
   ChunkReader& operator=(const ChunkReader&) = delete;
 
diff --git a/src/audio/include/fatfs_audio_input.hpp b/src/audio/include/fatfs_audio_input.hpp
index 5625d941..883441c2 100644
--- a/src/audio/include/fatfs_audio_input.hpp
+++ b/src/audio/include/fatfs_audio_input.hpp
@@ -28,6 +28,7 @@ class FatfsAudioInput : public IAudioElement {
       -> cpp::result<void, AudioProcessingError> override;
   auto ProcessChunk(const cpp::span<std::byte>& chunk)
       -> cpp::result<std::size_t, AudioProcessingError> override;
+  auto ProcessEndOfStream() -> void override;
   auto Process() -> cpp::result<void, AudioProcessingError> override;
 
   FatfsAudioInput(const FatfsAudioInput&) = delete;
diff --git a/src/audio/include/i2s_audio_output.hpp b/src/audio/include/i2s_audio_output.hpp
index 02ac7a16..b4fd4c59 100644
--- a/src/audio/include/i2s_audio_output.hpp
+++ b/src/audio/include/i2s_audio_output.hpp
@@ -4,6 +4,7 @@
 #include <memory>
 
 #include "audio_element.hpp"
+#include "chunk.hpp"
 #include "result.hpp"
 
 #include "dac.hpp"
@@ -21,13 +22,13 @@ class I2SAudioOutput : public IAudioElement {
                  std::unique_ptr<drivers::AudioDac> dac);
   ~I2SAudioOutput();
 
-  // TODO.
-  auto HasUnprocessedInput() -> bool override { return false; }
+  auto HasUnprocessedInput() -> bool override;
 
   auto ProcessStreamInfo(const StreamInfo& info)
       -> cpp::result<void, AudioProcessingError> override;
   auto ProcessChunk(const cpp::span<std::byte>& chunk)
       -> cpp::result<std::size_t, AudioProcessingError> override;
+  auto ProcessEndOfStream() -> void override;
   auto Process() -> cpp::result<void, AudioProcessingError> override;
 
   I2SAudioOutput(const I2SAudioOutput&) = delete;
@@ -37,11 +38,18 @@ class I2SAudioOutput : public IAudioElement {
   auto SetVolume(uint8_t volume) -> void;
   auto SetSoftMute(bool enabled) -> void;
 
+  auto ClearDmaQueue() -> void;
+
   drivers::GpioExpander* expander_;
   std::unique_ptr<drivers::AudioDac> dac_;
 
   uint8_t volume_;
   bool is_soft_muted_;
+
+  std::optional<ChunkReader> chunk_reader_;
+  cpp::span<std::byte> latest_chunk_;
+  std::optional<std::size_t> dma_size_;
+  QueueHandle_t dma_queue_;
 };
 
 }  // namespace audio
diff --git a/src/audio/include/stream_event.hpp b/src/audio/include/stream_event.hpp
index 4f441fa5..e84c8388 100644
--- a/src/audio/include/stream_event.hpp
+++ b/src/audio/include/stream_event.hpp
@@ -16,6 +16,7 @@ struct StreamEvent {
   static auto CreateChunkData(QueueHandle_t source, std::size_t chunk_size)
       -> StreamEvent*;
   static auto CreateChunkNotification(QueueHandle_t source) -> StreamEvent*;
+  static auto CreateEndOfStream(QueueHandle_t source) -> StreamEvent*;
 
   StreamEvent();
   ~StreamEvent();
@@ -28,6 +29,7 @@ struct StreamEvent {
     STREAM_INFO,
     CHUNK_DATA,
     CHUNK_NOTIFICATION,
+    END_OF_STREAM,
   } tag;
 
   union {
diff --git a/src/audio/stream_event.cpp b/src/audio/stream_event.cpp
index e3228680..6efebbca 100644
--- a/src/audio/stream_event.cpp
+++ b/src/audio/stream_event.cpp
@@ -37,6 +37,13 @@ auto StreamEvent::CreateChunkNotification(QueueHandle_t source)
   return event;
 }
 
+auto StreamEvent::CreateEndOfStream(QueueHandle_t source) -> StreamEvent* {
+  auto event = new StreamEvent;
+  event->tag = StreamEvent::END_OF_STREAM;
+  event->source = source;
+  return event;
+}
+
 StreamEvent::StreamEvent() : tag(StreamEvent::UNINITIALISED) {}
 
 StreamEvent::~StreamEvent() {
@@ -51,6 +58,8 @@ StreamEvent::~StreamEvent() {
       break;
     case CHUNK_NOTIFICATION:
       break;
+    case END_OF_STREAM:
+      break;
   }
 }
 
@@ -70,6 +79,8 @@ StreamEvent::StreamEvent(StreamEvent&& other) {
       break;
     case CHUNK_NOTIFICATION:
       break;
+    case END_OF_STREAM:
+      break;
   }
   other.tag = StreamEvent::UNINITIALISED;
 }
diff --git a/src/drivers/dac.cpp b/src/drivers/dac.cpp
index 214feb28..eec1959f 100644
--- a/src/drivers/dac.cpp
+++ b/src/drivers/dac.cpp
@@ -10,6 +10,7 @@
 #include "driver/i2s_types.h"
 #include "esp_err.h"
 #include "esp_log.h"
+#include "freertos/portmacro.h"
 #include "hal/i2c_types.h"
 
 #include "gpio_expander.hpp"
@@ -27,14 +28,22 @@ static const AudioDac::SampleRate kDefaultSampleRate =
     AudioDac::SAMPLE_RATE_44_1;
 static const AudioDac::BitsPerSample kDefaultBps = AudioDac::BPS_16;
 
+extern "C" {
+bool dma_callback(i2s_chan_handle_t handle,
+                  i2s_event_data_t* event,
+                  void* user_ctx) {
+  AudioDac* dac = static_cast<AudioDac*>(user_ctx);
+  return dac->WriteDataFromISR(static_cast<std::byte*>(event->data),
+                               event->size);
+}
+}
+
 auto AudioDac::create(GpioExpander* expander)
     -> cpp::result<std::unique_ptr<AudioDac>, Error> {
   // TODO: tune.
   i2s_chan_handle_t i2s_handle;
   i2s_chan_config_t channel_config =
       I2S_CHANNEL_DEFAULT_CONFIG(kI2SPort, I2S_ROLE_MASTER);
-  // Auto clear to trigger soft-mute when we run out of data.
-  channel_config.auto_clear = true;
   ESP_ERROR_CHECK(i2s_new_channel(&channel_config, &i2s_handle, NULL));
   //
   // First, instantiate the instance so it can do all of its power on
@@ -99,7 +108,8 @@ AudioDac::AudioDac(GpioExpander* gpio, i2s_chan_handle_t i2s_handle)
       i2s_handle_(i2s_handle),
       clock_config_(I2S_STD_CLK_DEFAULT_CONFIG(44100)),
       slot_config_(I2S_STD_MSB_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT,
-                                                   I2S_SLOT_MODE_STEREO)) {
+                                                   I2S_SLOT_MODE_STEREO)),
+      dma_queue_(nullptr) {
   gpio_->set_pin(GpioExpander::AUDIO_POWER_ENABLE, true);
   gpio_->Write();
 }
@@ -157,7 +167,9 @@ bool AudioDac::WaitForPowerState(
   return has_matched;
 }
 
-auto AudioDac::Reconfigure(BitsPerSample bps, SampleRate rate) -> bool {
+auto AudioDac::Reconfigure(BitsPerSample bps,
+                           SampleRate rate,
+                           QueueHandle_t dma_queue) -> std::size_t {
   // TODO(jacqueline): investigate how reliable the auto-clocking of the dac
   // is. We might need to explicit reconfigure the dac here as well if it's not
   // good enough.
@@ -171,20 +183,44 @@ auto AudioDac::Reconfigure(BitsPerSample bps, SampleRate rate) -> bool {
       bps == BPS_24 ? I2S_MCLK_MULTIPLE_384 : I2S_MCLK_MULTIPLE_256;
   ESP_ERROR_CHECK(i2s_channel_reconfig_std_clock(i2s_handle_, &clock_config_));
 
+  dma_queue_ = dma_queue;
+
+  // TODO: less spooky action here plz.
+  // dma_buffer_size = dma_frame_num (channel config) * slot_num (always 2?) *
+  // slot_bit_width / 8
+  //size_t dma_size = 240 * 2 * slot_config_.slot_bit_width / 8;
+  size_t dma_size = 960;
+  ESP_LOGI(kTag, "new dma size: %u bytes", dma_size);
+
+  i2s_event_callbacks_t callbacks = {
+      .on_recv = NULL,
+      .on_recv_q_ovf = NULL,
+      .on_sent = &dma_callback,
+      .on_send_q_ovf = NULL,
+  };
+  ESP_ERROR_CHECK(
+      i2s_channel_register_event_callback(i2s_handle_, &callbacks, this));
+
   ESP_ERROR_CHECK(i2s_channel_enable(i2s_handle_));
-  return true;
+
+  return dma_size;
 }
 
-auto AudioDac::WriteData(const cpp::span<std::byte>& data, TickType_t max_wait)
-    -> std::size_t {
-  std::size_t res = 0;
-  esp_err_t err =
-      i2s_channel_write(i2s_handle_, data.data(), data.size(), &res, max_wait);
-  if (err == ESP_ERR_TIMEOUT) {
-    return res;
+auto AudioDac::WriteDataFromISR(std::byte* data, std::size_t size) -> bool {
+  std::byte* new_data;
+  BaseType_t high_priority_task_awoken = pdFALSE;
+
+  if (xQueueReceiveFromISR(dma_queue_, &new_data, &high_priority_task_awoken)) {
+    // Item was received. Copy it into the DMA buffer.
+    memcpy(data, new_data, size);
+    free(new_data);
+    ESP_DRAM_LOGI(kTag, "wrote dma");
+  } else {
+    // No item was received. Write empty data.
+    memset(data, 0, size);
   }
-  ESP_ERROR_CHECK(err);
-  return res;
+
+  return high_priority_task_awoken;
 }
 
 void AudioDac::WriteRegister(Register reg, uint8_t val) {
diff --git a/src/drivers/display.cpp b/src/drivers/display.cpp
index 2ada4a3e..8d62cda2 100644
--- a/src/drivers/display.cpp
+++ b/src/drivers/display.cpp
@@ -49,7 +49,7 @@ namespace drivers {
 namespace callback {
 static std::atomic<Display*> instance = nullptr;
 
-static void flush_cb(lv_disp_drv_t* disp_drv,
+extern "C" void flush_cb(lv_disp_drv_t* disp_drv,
                      const lv_area_t* area,
                      lv_color_t* color_map) {
   auto instance_unwrapped = instance.load();
@@ -74,8 +74,9 @@ static void IRAM_ATTR post_cb(spi_transaction_t* transaction) {
 auto Display::create(GpioExpander* expander,
                      const displays::InitialisationData& init_data)
     -> cpp::result<std::unique_ptr<Display>, Error> {
-  expander->with(
-      [&](auto& gpio) { gpio.set_pin(GpioExpander::DISPLAY_LED, 1); });
+  expander->set_pin(GpioExpander::DISPLAY_LED, 0);
+  expander->set_pin(GpioExpander::DISPLAY_POWER_ENABLE, 1);
+  expander->Write();
 
   // Next, init the SPI device
   spi_device_interface_config_t spi_cfg = {
@@ -182,6 +183,7 @@ void Display::SendTransaction(TransactionType type,
   if (length == 0) {
     return;
   }
+  ESP_LOGI(kTag, "lvgl transaction");
 
   // TODO: Use a memory pool for these.
   spi_transaction_t* transaction = (spi_transaction_t*)heap_caps_calloc(
diff --git a/src/drivers/display_init.cpp b/src/drivers/display_init.cpp
index e66d6a47..293ea5a2 100644
--- a/src/drivers/display_init.cpp
+++ b/src/drivers/display_init.cpp
@@ -96,7 +96,7 @@ static const uint8_t kST7735RCommonFooter[]{
 
 const InitialisationData kST7735R = {
     .num_sequences = 3,
-    .sequences = {kST7735RCommonHeader, kST7735RCommonRed,
+    .sequences = {kST7735RCommonHeader, kST7735RCommonGreen,
                   kST7735RCommonFooter}};
 
 }  // namespace displays
diff --git a/src/drivers/include/dac.hpp b/src/drivers/include/dac.hpp
index aec89c72..698019b7 100644
--- a/src/drivers/include/dac.hpp
+++ b/src/drivers/include/dac.hpp
@@ -4,6 +4,7 @@
 
 #include <functional>
 #include <memory>
+#include <optional>
 #include <utility>
 
 #include "driver/i2s_std.h"
@@ -66,11 +67,11 @@ class AudioDac {
   };
 
   // TODO(jacqueline): worth supporting channels here as well?
-  auto Reconfigure(BitsPerSample bps, SampleRate rate) -> bool;
-
-  auto WriteData(const cpp::span<std::byte>& data, TickType_t max_wait)
+  auto Reconfigure(BitsPerSample bps, SampleRate rate, QueueHandle_t dma_queue)
       -> std::size_t;
 
+  auto WriteDataFromISR(std::byte* data, std::size_t size) -> bool;
+
   // Not copyable or movable.
   AudioDac(const AudioDac&) = delete;
   AudioDac& operator=(const AudioDac&) = delete;
@@ -82,6 +83,9 @@ class AudioDac {
   i2s_std_clk_config_t clock_config_;
   i2s_std_slot_config_t slot_config_;
 
+  // TODO: volatile?
+  volatile QueueHandle_t dma_queue_;
+
   /*
    * Pools the power state for up to 10ms, waiting for the given predicate to
    * be true.
diff --git a/src/main/main.cpp b/src/main/main.cpp
index fde416ce..08b31cd3 100644
--- a/src/main/main.cpp
+++ b/src/main/main.cpp
@@ -48,7 +48,7 @@ struct LvglArgs {
   drivers::GpioExpander* gpio_expander;
 };
 
-void lvgl_main(void* voidArgs) {
+extern "C" void lvgl_main(void* voidArgs) {
   ESP_LOGI(TAG, "starting LVGL task");
   LvglArgs* args = (LvglArgs*)voidArgs;
   drivers::GpioExpander* gpio_expander = args->gpio_expander;
@@ -97,10 +97,10 @@ extern "C" void app_main(void) {
 
   ESP_LOGI(TAG, "Enable power rails for development");
   expander->with([&](auto& gpio) {
-    gpio.set_pin(drivers::GpioExpander::AUDIO_POWER_ENABLE, 1);
-    gpio.set_pin(drivers::GpioExpander::SD_CARD_POWER_ENABLE, 1);
+    gpio.set_pin(drivers::GpioExpander::USB_INTERFACE_POWER_ENABLE, 0);
+    gpio.set_pin(drivers::GpioExpander::SD_CARD_POWER_ENABLE, 0);
     gpio.set_pin(drivers::GpioExpander::SD_MUX_SWITCH,
-                 drivers::GpioExpander::SD_MUX_ESP);
+                 drivers::GpioExpander::SD_MUX_USB);
   });
 
   ESP_LOGI(TAG, "Init battery measurement");