1 files changed, 208 insertions, 0 deletions
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