[refactor] Move screen class to separate file.

screen.py

@@ -0,0 +1,67 @@
+from machine import Pin, SPI
+import _thread
+from st7789 import ST7789
+from framebuf import FrameBuffer, RGB565
+
+
+
+def color565(red: int, green: int, blue: int) -> int:
+    """Convert RGB888 to RGB565."""
+    return (
+        (((green & 0b00011100) << 3) + ((red & 0b11111000) >> 3) << 8) 
+        + (blue & 0b11111000) 
+        + ((green & 0b11100000) >> 5)
+        )
+
+
+RED = color565(0, 0, 255)
+GREEN = color565(0, 255, 0)
+YELLOW = color565(0, 255, 255)
+BLACK = color565(0, 0, 0)
+WHITE = color565(255, 255, 255)
+
+
+class Screen:
+    """Class to handle the ST7789 display and framebuffer."""
+    def __init__(self, width: int, height: int, rotation: int):
+        self.spi: SPI = SPI(1,
+            baudrate=31250000,
+            polarity=1,
+            phase=1,
+            bits=8,
+            firstbit=SPI.MSB,
+            sck=Pin(10),
+            mosi=Pin(11))
+        self.width: int = width 
+        self.height: int = height
+        self.rotation: int = rotation
+        self.display = ST7789(
+            self.spi,
+            self.height,
+            self.width,
+            reset=Pin(12, Pin.OUT),
+            cs=Pin(9, Pin.OUT),
+            dc=Pin(8, Pin.OUT),
+            backlight=Pin(13, Pin.OUT),
+            rotation=self.rotation)
+        # FrameBuffer needs 2 bytes for every RGB565 pixel
+        self.buffer_width = self.width
+        self.buffer_height = self.height + 1
+        self.buffer = bytearray(self.buffer_width * self.buffer_height * 2)
+        self.fbuf: FrameBuffer = FrameBuffer(self.buffer, self.buffer_width, self.buffer_height, RGB565)
+        self.render_frame = False
+    
+    def refresh(self):
+        self.display.blit_buffer(self.buffer, 0, 0, self.buffer_width, self.buffer_height)
+
+    def clear(self, refresh: bool = True):
+        self.fbuf.fill(BLACK)
+        if refresh:
+            self.refresh()
+
+    def render_thread(self):
+        """Threaded function to handle SPI rendering on a separate core."""
+        self.display.blit_buffer(self.buffer, 0, 0, self.buffer_width, self.buffer_height)
+        self.fbuf.fill(BLACK)
+        self.render_frame = False
+        # thread will exit and self clean removing need for garbage collection