[lcd] add support for operating on virtual framebuffers

Current implementation contains full support for:
- transparent switching between direct and framebuffer rendering modes
- writing characters to framebuffers
- loading frame from memory to physical display

As well as partial support for instruction writes including:
- resetting the display (clears memory, sets cursor at 0:0, switches to increment mode)
- switching between increment/decrement modes
- setting cursor position

Core/Inc/lcd.h

@@ -7,6 +7,8 @@
 #define DISPLAY_RW  ((uint16_t) (0x1U << 10))
 #define DISPLAY_ENA ((uint16_t) (0x1U << 11))
 
+#define DISPLAY_FRAMES_AVAILABLE 14
+
 #define DISPLAY_POLL_UNTIL_READY do { while (display_read_status() & 0x80) {} } while (0)
 
 #define DISPLAY_SET_INCREMENT do { display_write_instruction_byte(0x06); } while (0)
@@ -16,11 +18,16 @@
 
 #define DISPLAY_CLEAR do { display_write_instruction_byte(0x01); } while (0)
 
+struct Display_emu_state {
+	size_t cursor_offset:5;
+	size_t next:1;
+};
 
 void display_init(void);
-uint8_t display_read_status(void);
 void display_write_instruction_byte(uint8_t code);
 void display_write_data_byte(uint8_t code);
 void display_write_data_seq(char *codes);
+void display_to_framebuffer(void);
+void display_to_direct(void);
 
 #endif

Core/Inc/main.h

@@ -32,6 +32,8 @@ extern "C" {
 /* Private includes ----------------------------------------------------------*/
 /* USER CODE BEGIN Includes */
 
+#include <string.h>
+
 /* USER CODE END Includes */
 
 /* Exported types ------------------------------------------------------------*/