Add initial implementation of EInkDisplay from CidVonHighwind (#4)

libs/display/EInkDisplay/include/EInkDisplay.h

@@ -0,0 +1,93 @@
+#pragma once
+#include <Arduino.h>
+#include <SPI.h>
+
+class EInkDisplay {
+ public:
+  // Constructor with pin configuration
+  EInkDisplay(int8_t sclk, int8_t mosi, int8_t cs, int8_t dc, int8_t rst, int8_t busy);
+
+  // Destructor
+  ~EInkDisplay();
+
+  // Refresh modes (guarded to avoid redefinition in test builds)
+  enum RefreshMode {
+    FULL_REFRESH,  // Full refresh with complete waveform
+    HALF_REFRESH,  // Half refresh (1720ms) - balanced quality and speed
+    FAST_REFRESH   // Fast refresh using custom LUT
+  };
+
+  // Initialize the display hardware and driver
+  void begin();
+
+  // Display dimensions
+  static const uint16_t DISPLAY_WIDTH = 800;
+  static const uint16_t DISPLAY_HEIGHT = 480;
+  static const uint16_t DISPLAY_WIDTH_BYTES = DISPLAY_WIDTH / 8;
+  static const uint32_t BUFFER_SIZE = DISPLAY_WIDTH_BYTES * DISPLAY_HEIGHT;
+
+  // Frame buffer operations
+  void clearScreen(uint8_t color = 0xFF);
+  void drawImage(const uint8_t* imageData, uint16_t x, uint16_t y, uint16_t w, uint16_t h, bool fromProgmem = false);
+
+  void swapBuffers();
+  void setFramebuffer(const uint8_t* bwBuffer);
+
+  void copyGrayscaleBuffers(const uint8_t* lsbBuffer, const uint8_t* msbBuffer);
+  void copyGrayscaleLsbBuffers(const uint8_t* lsbBuffer);
+  void copyGrayscaleMsbBuffers(const uint8_t* msbBuffer);
+
+  void displayBuffer(RefreshMode mode = FAST_REFRESH);
+  void displayGrayBuffer(bool turnOffScreen = false);
+
+  void refreshDisplay(RefreshMode mode = FAST_REFRESH, bool turnOffScreen = false);
+
+  // debug function
+  void grayscaleRevert();
+
+  // LUT control
+  void setCustomLUT(bool enabled, const unsigned char* lutData = nullptr);
+
+  // Power management
+  void deepSleep();
+
+  // Access to frame buffer
+  uint8_t* getFrameBuffer() {
+    return frameBuffer;
+  }
+
+  // Save the current framebuffer to a PBM file (desktop/test builds only)
+  void saveFrameBufferAsPBM(const char* filename);
+
+ private:
+  // Pin configuration
+  int8_t _sclk, _mosi, _cs, _dc, _rst, _busy;
+
+  // Frame buffer (statically allocated)
+  uint8_t frameBuffer0[BUFFER_SIZE];
+  uint8_t frameBuffer1[BUFFER_SIZE];
+
+  uint8_t* frameBuffer;
+  uint8_t* frameBufferActive;
+
+  // SPI settings
+  SPISettings spiSettings;
+
+  // State
+  bool isScreenOn;
+  bool customLutActive;
+  bool inGrayscaleMode;
+  bool drawGrayscale;
+
+  // Low-level display control
+  void resetDisplay();
+  void sendCommand(uint8_t command);
+  void sendData(uint8_t data);
+  void sendData(const uint8_t* data, uint16_t length);
+  void waitWhileBusy(const char* comment = nullptr);
+  void initDisplayController();
+
+  // Low-level display operations
+  void setRamArea(uint16_t x, uint16_t y, uint16_t w, uint16_t h);
+  void writeRamBuffer(uint8_t ramBuffer, const uint8_t* data, uint32_t size);
+};