8 files changed, 656 insertions, 0 deletions
diff --git a/src/drivers/include/battery.hpp b/src/drivers/include/battery.hpp
new file mode 100644
index 00000000..399e866f
--- /dev/null
+++ b/src/drivers/include/battery.hpp
@@ -0,0 +1,16 @@
+#pragma once
+
+#include <stdint.h>
+
+#include "esp_err.h"
+
+namespace gay_ipod {
+
+esp_err_t init_adc(void);
+
+/**
+ * Returns the current battery level in millivolts.
+ */
+uint32_t read_battery_voltage(void);
+
+}  // namespace gay_ipod
diff --git a/src/drivers/include/dac.hpp b/src/drivers/include/dac.hpp
new file mode 100644
index 00000000..6d025384
--- /dev/null
+++ b/src/drivers/include/dac.hpp
@@ -0,0 +1,73 @@
+#pragma once
+
+#include "gpio-expander.hpp"
+
+#include <stdint.h>
+#include <functional>
+
+#include "esp_err.h"
+#include "result.hpp"
+
+namespace gay_ipod {
+
+/**
+ * Interface for a PCM5122PWR DAC, configured over I2C.
+ */
+class AudioDac {
+ public:
+  enum Error {
+    FAILED_TO_BOOT,
+    FAILED_TO_CONFIGURE,
+  };
+  static auto create(GpioExpander* expander)
+      -> cpp::result<std::unique_ptr<AudioDac>, Error>;
+
+  AudioDac(GpioExpander* gpio);
+  ~AudioDac();
+
+  /**
+   * Sets the volume on a scale from 0 (loudest) to 254 (quietest). A value of
+   * 255 engages the soft mute function.
+   */
+  void WriteVolume(uint8_t volume);
+
+  enum PowerState {
+    POWERDOWN = 0b0,
+    WAIT_FOR_CP = 0b1,
+    CALIBRATION_1 = 0b10,
+    CALIBRATION_2 = 0b11,
+    RAMP_UP = 0b100,
+    RUN = 0b101,
+    SHORT = 0b110,
+    RAMP_DOWN = 0b111,
+    STANDBY = 0b1000,
+  };
+
+  /* Returns the current boot-up status and internal state of the DAC */
+  std::pair<bool, PowerState> ReadPowerState();
+
+  // Not copyable or movable.
+  AudioDac(const AudioDac&) = delete;
+  AudioDac& operator=(const AudioDac&) = delete;
+
+ private:
+  GpioExpander* gpio_;
+
+  /*
+   * Pools the power state for up to 10ms, waiting for the given predicate to
+   * be true.
+   */
+  bool WaitForPowerState(std::function<bool(bool, PowerState)> predicate);
+
+  enum Register {
+    PAGE_SELECT = 0,
+    DE_EMPHASIS = 7,
+    DIGITAL_VOLUME_L = 61,
+    DIGITAL_VOLUME_R = 62,
+    DSP_BOOT_POWER_STATE = 118,
+  };
+
+  void WriteRegister(Register reg, uint8_t val);
+};
+
+}  // namespace gay_ipod
diff --git a/src/drivers/include/display-init.hpp b/src/drivers/include/display-init.hpp
new file mode 100644
index 00000000..f11e9b57
--- /dev/null
+++ b/src/drivers/include/display-init.hpp
@@ -0,0 +1,81 @@
+#pragma once
+
+#include <cstdint>
+
+namespace gay_ipod {
+namespace displays {
+
+extern const uint8_t kDelayBit;
+
+struct InitialisationData {
+  uint8_t num_sequences;
+  const uint8_t* sequences[4];
+};
+
+extern const InitialisationData kST7735R;
+
+/*
+ * Valid command bytes that can be sent to ST77XX displays, as well as commands
+ * for more specific variants.
+ */
+enum StCommands {
+  ST77XX_NOP = 0x00,
+  ST77XX_SWRESET = 0x01,
+  ST77XX_RDDID = 0x04,
+  ST77XX_RDDST = 0x09,
+
+  ST77XX_SLPIN = 0x10,
+  ST77XX_SLPOUT = 0x11,
+  ST77XX_PTLON = 0x12,
+  ST77XX_NORON = 0x13,
+
+  ST77XX_INVOFF = 0x20,
+  ST77XX_INVON = 0x21,
+  ST77XX_DISPOFF = 0x28,
+  ST77XX_DISPON = 0x29,
+  ST77XX_CASET = 0x2A,
+  ST77XX_RASET = 0x2B,
+  ST77XX_RAMWR = 0x2C,
+  ST77XX_RAMRD = 0x2E,
+
+  ST77XX_PTLAR = 0x30,
+  ST77XX_TEOFF = 0x34,
+  ST77XX_TEON = 0x35,
+  ST77XX_MADCTL = 0x36,
+  ST77XX_COLMOD = 0x3A,
+
+  ST77XX_MADCTL_MY = 0x80,
+  ST77XX_MADCTL_MX = 0x40,
+  ST77XX_MADCTL_MV = 0x20,
+  ST77XX_MADCTL_ML = 0x10,
+  ST77XX_MADCTL_RGB = 0x00,
+
+  ST77XX_RDID1 = 0xDA,
+  ST77XX_RDID2 = 0xDB,
+  ST77XX_RDID3 = 0xDC,
+  ST77XX_RDID4 = 0xDD,
+
+  ST7735_MADCTL_BGR = 0x08,
+  ST7735_MADCTL_MH = 0x04,
+
+  ST7735_FRMCTR1 = 0xB1,
+  ST7735_FRMCTR2 = 0xB2,
+  ST7735_FRMCTR3 = 0xB3,
+  ST7735_INVCTR = 0xB4,
+  ST7735_DISSET5 = 0xB6,
+
+  ST7735_PWCTR1 = 0xC0,
+  ST7735_PWCTR2 = 0xC1,
+  ST7735_PWCTR3 = 0xC2,
+  ST7735_PWCTR4 = 0xC3,
+  ST7735_PWCTR5 = 0xC4,
+  ST7735_VMCTR1 = 0xC5,
+
+  ST7735_PWCTR6 = 0xFC,
+
+  ST7735_GMCTRP1 = 0xE0,
+  ST7735_GMCTRN1 = 0xE1,
+};
+
+}  // namespace displays
+}  // namespace gay_ipod
diff --git a/src/drivers/include/display.hpp b/src/drivers/include/display.hpp
new file mode 100644
index 00000000..2d6e9cd6
--- /dev/null
+++ b/src/drivers/include/display.hpp
@@ -0,0 +1,67 @@
+#pragma once
+
+#include <cstdint>
+#include "display-init.hpp"
+#include "driver/spi_master.h"
+#include "gpio-expander.hpp"
+#include "lvgl/lvgl.h"
+#include "result.hpp"
+
+namespace gay_ipod {
+
+/*
+ * Display driver for LVGL.
+ */
+class Display {
+ public:
+  enum Error {};
+  static auto create(GpioExpander* expander,
+                     const displays::InitialisationData& init_data)
+      -> cpp::result<std::unique_ptr<Display>, Error>;
+
+  Display(GpioExpander* gpio, spi_device_handle_t handle);
+  ~Display();
+
+  void WriteData();
+
+  void Flush(lv_disp_drv_t* disp_drv,
+             const lv_area_t* area,
+             lv_color_t* color_map);
+
+  void IRAM_ATTR PostTransaction(const spi_transaction_t& transaction);
+
+  void ServiceTransactions();
+
+ private:
+  GpioExpander* gpio_;
+  spi_device_handle_t handle_;
+
+  lv_disp_draw_buf_t buffers_;
+  lv_disp_drv_t driver_;
+  lv_disp_t* display_ = nullptr;
+
+  enum TransactionType {
+    COMMAND = 0,
+    DATA = 1,
+  };
+
+  enum TransactionFlags {
+    LVGL_FLUSH = 1,
+  };
+
+  void SendInitialisationSequence(const uint8_t* data);
+
+  void SendCommandWithData(uint8_t command,
+                           const uint8_t* data,
+                           size_t length,
+                           uintptr_t flags = 0);
+
+  void SendCmd(const uint8_t* data, size_t length, uintptr_t flags = 0);
+  void SendData(const uint8_t* data, size_t length, uintptr_t flags = 0);
+  void SendTransaction(TransactionType type,
+                       const uint8_t* data,
+                       size_t length,
+                       uintptr_t flags = 0);
+};
+
+}  // namespace gay_ipod
diff --git a/src/drivers/include/gpio-expander.hpp b/src/drivers/include/gpio-expander.hpp
new file mode 100644
index 00000000..2a12fba4
--- /dev/null
+++ b/src/drivers/include/gpio-expander.hpp
@@ -0,0 +1,208 @@
+#pragma once
+
+#include <stdint.h>
+#include <atomic>
+#include <functional>
+#include <mutex>
+#include <tuple>
+#include <utility>
+
+#include "driver/i2c.h"
+#include "esp_check.h"
+#include "esp_err.h"
+#include "esp_log.h"
+#include "freertos/FreeRTOS.h"
+
+namespace gay_ipod {
+
+/**
+ * Wrapper for interfacing with the PCA8575 GPIO expander. Includes basic
+ * low-level pin setting methods, as well as higher level convenience functions
+ * for reading, writing, and atomically interacting with the SPI chip select
+ * pins.
+ *
+ * Each method of this class can be called safely from any thread, and all
+ * updates are guaranteed to be atomic. Any access to chip select related pins
+ * should be done whilst holding `cs_lock` (preferably via the helper methods).
+ */
+class GpioExpander {
+ public:
+  GpioExpander();
+  ~GpioExpander();
+
+  static const uint8_t kPca8575Address = 0x20;
+  static const uint8_t kPca8575Timeout = 100 / portTICK_RATE_MS;
+
+  // Port A:
+  // 0 - audio power enable
+  // 1 - usb interface power enable
+  // 2 - display power enable
+  // 3 - sd card power enable
+  // 4 - charge power ok (active low)
+  // 5 - sd mux switch
+  // 6 - sd chip select
+  // 7 - display chip select
+  // All power switches low, chip selects high, active-low charge power high
+  static const uint8_t kPortADefault = 0b11010001;
+
+  // Port B:
+  // 0 - 3.5mm jack detect (active low)
+  // 1 - dac soft mute switch
+  // 2 - GPIO
+  // 3 - GPIO
+  // 4 - GPIO
+  // 5 - GPIO
+  // 6 - GPIO
+  // 7 - GPIO
+  // DAC mute output low, everything else is active-low inputs.
+  static const uint8_t kPortBDefault = 0b11111111;
+
+  /*
+   * Convenience mehod for packing the port a and b bytes into a single 16 bit
+   * value.
+   */
+  static uint16_t pack(uint8_t a, uint8_t b) { return ((uint16_t)b) << 8 | a; }
+
+  /*
+   * Convenience mehod for unpacking the result of `pack` back into two single
+   * byte port datas.
+   */
+  static std::pair<uint8_t, uint8_t> unpack(uint16_t ba) {
+    return std::pair((uint8_t)ba, (uint8_t)(ba >> 8));
+  }
+
+  /*
+   * Convenience function for running some arbitrary pin writing code, then
+   * flushing a `Write()` to the expander. Example usage:
+   *
+   * ```
+   * gpio_.with([&](auto& gpio) {
+   *	gpio.set_pin(AUDIO_POWER_ENABLE, true);
+   * });
+   * ```
+   */
+  void with(std::function<void(GpioExpander&)> f);
+
+  /**
+   * Sets the ports on the GPIO expander to the values currently represented
+   * in `ports`.
+   */
+  esp_err_t Write(void);
+
+  /**
+   * Reads from the GPIO expander, populating `inputs` with the most recent
+   * values.
+   */
+  esp_err_t Read(void);
+
+  /* Maps each pin of the expander to its number in a `pack`ed uint16. */
+  enum Pin {
+    // Port A
+    AUDIO_POWER_ENABLE = 0,
+    USB_INTERFACE_POWER_ENABLE = 1,
+    DISPLAY_POWER_ENABLE = 2,
+    SD_CARD_POWER_ENABLE = 3,
+    CHARGE_POWER_OK = 4,  // Active-low input
+    SD_MUX_SWITCH = 5,
+    SD_CHIP_SELECT = 6,
+    DISPLAY_CHIP_SELECT = 7,
+
+    // Port B
+    PHONE_DETECT = 8,  // Active-high input
+    DAC_MUTE = 9,
+    GPIO_1 = 10,
+    GPIO_2 = 11,
+    GPIO_3 = 12,
+    GPIO_4 = 13,
+    GPIO_5 = 14,
+    GPIO_6 = 15,
+  };
+
+  /* Pins whose access should be guarded by `cs_lock`. */
+  enum ChipSelect {
+    SD_CARD = SD_CHIP_SELECT,
+    DISPLAY = DISPLAY_CHIP_SELECT,
+  };
+
+  /* Nicer value names for use with the SD_MUX_SWITCH pin. */
+  enum SdController {
+    SD_MUX_ESP = 0,
+    SD_MUX_USB = 1,
+  };
+
+  /**
+   * Returns the current driven status of each of the ports. The first byte is
+   * port a, and the second byte is port b.
+   */
+  std::atomic<uint16_t>& ports() { return ports_; }
+
+  /*
+   * Sets a single specific pin to the given value. `true` corresponds to
+   * HIGH, and `false` corresponds to LOW.
+   *
+   * Calls to this method will be buffered in memory until a call to `Write()`
+   * is made.
+   */
+  void set_pin(Pin pin, bool value);
+  void set_pin(ChipSelect cs, bool value);
+
+  /**
+   * Returns the input status of each of the ports. The first byte is port a,
+   * and the second byte is port b.
+   */
+  const std::atomic<uint16_t>& inputs() const { return inputs_; }
+
+  /* Returns the most recently cached value of the given pin. Only valid for
+   * pins used as inputs; to check what value we're driving a pin, use
+   * `ports()`.
+   */
+  bool get_input(Pin pin) const;
+
+  /* Returns the mutex that must be held whilst pulling a CS pin low. */
+  std::mutex& cs_mutex() { return cs_mutex_; }
+
+  /*
+   * Helper class containing an active `cs_mutex` lock. When an instance of
+   * this class is destroyed (usually by falling out of scope), the associated
+   * CS pin will be driven high before the lock is released.
+   */
+  class SpiLock {
+   public:
+    SpiLock(GpioExpander& gpio, ChipSelect cs);
+    ~SpiLock();
+
+    SpiLock(const SpiLock&) = delete;
+
+   private:
+    std::scoped_lock<std::mutex> lock_;
+    GpioExpander& gpio_;
+    ChipSelect cs_;
+  };
+
+  /*
+   * Pulls the given CS pin low to signal that we are about to communicate
+   * with a particular device, after acquiring a lock on `cs_mutex`. The
+   * recommended way to safely interact with devices on the SPI bus is to have
+   * a self-contained block like so:
+   *
+   * ```
+   * {
+   *	auto lock = AcquireSpiBus(WHATEVER);
+   *  // Do some cool things here.
+   * }
+   * ```
+   */
+  SpiLock AcquireSpiBus(ChipSelect cs);
+
+  // Not copyable or movable. There should usually only ever be once instance
+  // of this class, and that instance will likely have a static lifetime.
+  GpioExpander(const GpioExpander&) = delete;
+  GpioExpander& operator=(const GpioExpander&) = delete;
+
+ private:
+  std::mutex cs_mutex_;
+  std::atomic<uint16_t> ports_;
+  std::atomic<uint16_t> inputs_;
+};
+
+}  // namespace gay_ipod
diff --git a/src/drivers/include/i2c.hpp b/src/drivers/include/i2c.hpp
new file mode 100644
index 00000000..db554f5d
--- /dev/null
+++ b/src/drivers/include/i2c.hpp
@@ -0,0 +1,84 @@
+#pragma once
+
+#include <cstdint>
+
+#include "driver/i2c.h"
+#include "hal/i2c_types.h"
+
+namespace gay_ipod {
+
+/*
+ * Convenience wrapper for performing an I2C transaction with a reasonable
+ * preconfigured timeout, automatic management of a heap-based command buffer,
+ * and a terser API for enqueuing bytes.
+ *
+ * Any error codes from the underlying ESP IDF are treated as fatal, since they
+ * typically represent invalid arguments or OOMs.
+ */
+class I2CTransaction {
+ public:
+  static const uint8_t kI2CTimeout = 100 / portTICK_RATE_MS;
+
+  I2CTransaction();
+  ~I2CTransaction();
+
+  /*
+   * Executes all enqueued commands, returning the result code. Possible error
+   * codes, per the ESP-IDF docs:
+   *
+   * ESP_OK Success
+   * ESP_ERR_INVALID_ARG Parameter error
+   * ESP_FAIL Sending command error, slave doesn’t ACK the transfer.
+   * ESP_ERR_INVALID_STATE I2C driver not installed or not in master mode.
+   * ESP_ERR_TIMEOUT Operation timeout because the bus is busy.
+   */
+  esp_err_t Execute();
+
+  /*
+   * Enqueues a start condition. May also be used for repeated start
+   * conditions.
+   */
+  I2CTransaction& start();
+  /* Enqueues a stop condition. */
+  I2CTransaction& stop();
+
+  /*
+   * Enqueues writing the given 7 bit address, followed by one bit indicating
+   * whether this is a read or write request.
+   *
+   * This command will expect an ACK before continuing.
+   */
+  I2CTransaction& write_addr(uint8_t addr, uint8_t op);
+
+  /*
+   * Enqueues one or more bytes to be written. The transaction will wait for
+   * an ACK to be returned before writing the next byte.
+   */
+  I2CTransaction& write_ack(uint8_t data);
+  template <typename... More>
+  I2CTransaction& write_ack(uint8_t data, More... more) {
+    write_ack(data);
+    write_ack(more...);
+    return *this;
+  }
+
+  /*
+   * Enqueues a read of one byte into the given uint8. Responds with the given
+   * ACK/NACK type.
+   */
+  I2CTransaction& read(uint8_t* dest, i2c_ack_type_t ack);
+
+  /* Returns the underlying command buffer. */
+  i2c_cmd_handle_t handle() { return handle_; }
+
+  // Cannot be moved or copied, since doing so is probably an error. Pass a
+  // reference instead.
+  I2CTransaction(const I2CTransaction&) = delete;
+  I2CTransaction& operator=(const I2CTransaction&) = delete;
+
+ private:
+  i2c_cmd_handle_t handle_;
+  uint8_t* buffer_;
+};
+
+}  // namespace gay_ipod
diff --git a/src/drivers/include/playback.hpp b/src/drivers/include/playback.hpp
new file mode 100644
index 00000000..493dd311
--- /dev/null
+++ b/src/drivers/include/playback.hpp
@@ -0,0 +1,67 @@
+#pragma once
+
+#include "dac.hpp"
+#include "storage.hpp"
+
+#include <cstdint>
+#include <memory>
+#include <string>
+
+#include "audio_common.h"
+#include "audio_element.h"
+#include "audio_event_iface.h"
+#include "audio_pipeline.h"
+#include "esp_err.h"
+#include "fatfs_stream.h"
+#include "i2s_stream.h"
+#include "mp3_decoder.h"
+#include "result.hpp"
+
+namespace gay_ipod {
+
+class DacAudioPlayback {
+ public:
+  enum Error { PIPELINE_INIT };
+  static auto create(AudioDac* dac)
+      -> cpp::result<std::unique_ptr<DacAudioPlayback>, Error>;
+
+  DacAudioPlayback(AudioDac* dac,
+                   audio_pipeline_handle_t pipeline,
+                   audio_element_handle_t fatfs_stream_reader,
+                   audio_element_handle_t i2s_stream_writer,
+                   audio_event_iface_handle_t event_interface,
+                   audio_element_handle_t mp3_decoder);
+  ~DacAudioPlayback();
+
+  void Play(const std::string& filename);
+  void Resume();
+  void Pause();
+
+  void ProcessEvents();
+
+  /* for gapless */
+  void set_next_file(const std::string& filename);
+
+  void set_volume(uint8_t volume);
+  auto volume() -> uint8_t;
+
+  // Not copyable or movable.
+  DacAudioPlayback(const DacAudioPlayback&) = delete;
+  DacAudioPlayback& operator=(const DacAudioPlayback&) = delete;
+
+ private:
+  AudioDac* dac_;
+  std::mutex playback_lock_;
+
+  std::string next_filename_;
+  uint8_t volume_;
+
+  audio_pipeline_handle_t pipeline_;
+  audio_element_handle_t fatfs_stream_reader_;
+  audio_element_handle_t i2s_stream_writer_;
+  audio_event_iface_handle_t event_interface_;
+
+  audio_element_handle_t mp3_decoder_;
+};
+
+}  // namespace gay_ipod
diff --git a/src/drivers/include/storage.hpp b/src/drivers/include/storage.hpp
new file mode 100644
index 00000000..cee49cc5
--- /dev/null
+++ b/src/drivers/include/storage.hpp
@@ -0,0 +1,60 @@
+#pragma once
+
+#include "gpio-expander.hpp"
+
+#include <memory>
+
+#include "driver/sdmmc_types.h"
+#include "driver/sdspi_host.h"
+#include "esp_err.h"
+#include "esp_vfs_fat.h"
+#include "result.hpp"
+
+namespace gay_ipod {
+
+extern const char* kStoragePath;
+
+class SdStorage {
+ public:
+  enum Error {
+    FAILED_TO_INIT,
+    /** We couldn't interact with the SD card at all. Is it missing? */
+    FAILED_TO_READ,
+    /** We couldn't mount the SD card. Is it formatted? */
+    FAILED_TO_MOUNT,
+  };
+
+  static auto create(GpioExpander* gpio)
+      -> cpp::result<std::unique_ptr<SdStorage>, Error>;
+
+  SdStorage(GpioExpander* gpio,
+            esp_err_t (*do_transaction)(sdspi_dev_handle_t, sdmmc_command_t*),
+            sdspi_dev_handle_t handle_,
+            std::unique_ptr<sdmmc_host_t>& host_,
+            std::unique_ptr<sdmmc_card_t>& card_,
+            FATFS* fs_);
+  ~SdStorage();
+
+  auto HandleTransaction(sdspi_dev_handle_t handle, sdmmc_command_t* cmdinfo)
+      -> esp_err_t;
+
+  // Not copyable or movable.
+  // TODO: maybe this could be movable?
+  SdStorage(const SdStorage&) = delete;
+  SdStorage& operator=(const SdStorage&) = delete;
+
+ private:
+  GpioExpander* gpio_;
+
+  esp_err_t (*do_transaction_)(sdspi_dev_handle_t, sdmmc_command_t*) = nullptr;
+
+  // SPI and SD driver info
+  sdspi_dev_handle_t handle_;
+  std::unique_ptr<sdmmc_host_t> host_;
+  std::unique_ptr<sdmmc_card_t> card_;
+
+  // Filesystem info
+  FATFS* fs_ = nullptr;
+};
+
+}  // namespace gay_ipod