Add libraries, picocalc notes.

libraries/TFT_eSPI/examples/Sprite/One_bit_Yin_Yang/One_bit_Yin_Yang.ino

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+// This sketch draws a rotating Yin and Yang symbol. It illustrates
+// the drawing and rendering of simple animated graphics using
+// a 1 bit per pixel (1 bpp) Sprite.
+
+// Note:  TFT_BLACK sets the pixel value to 0
+// Any other colour sets the pixel value to 1
+
+// A square sprite of side = 2 x RADIUS will be created
+// (80 * 80)/8 = 800 bytes needed for 1 bpp sprite
+//              6400 bytes for 8 bpp
+//             12800 bytes for 16 bpp
+#define RADIUS 40      // Radius of completed symbol = 40
+
+#define WAIT 0         // Loop delay
+
+// 1bpp Sprites are economical on memory but slower to render
+#define COLOR_DEPTH 1  // Colour depth (1, 8 or 16 bits per pixel)
+
+// Rotation angle increment and start angle
+#define ANGLE_INC 3
+int angle = 0;
+
+#include <TFT_eSPI.h>                 // Hardware-specific library
+
+TFT_eSPI    tft = TFT_eSPI();         // Invoke library
+
+TFT_eSprite img = TFT_eSprite(&tft);  // Sprite class
+
+
+// -------------------------------------------------------------------------
+void setup(void)
+{
+  tft.begin();
+  tft.setRotation(0);
+  tft.fillScreen(TFT_BLUE);
+
+  img.setColorDepth(COLOR_DEPTH);
+  img.createSprite(RADIUS*2+1, RADIUS*2+1);
+  img.fillSprite(TFT_BLACK);
+}
+// -------------------------------------------------------------------------
+// -------------------------------------------------------------------------
+void loop() {
+  // Draw Yin and Yang symbol circles into Sprite
+  yinyang(RADIUS, RADIUS, angle, RADIUS);
+
+  // Set the 2 pixel palette colours that 1 and 0 represent on the display screen
+  img.setBitmapColor(TFT_WHITE, TFT_BLACK); 
+
+  // Push Sprite image to the TFT screen at x, y
+  img.pushSprite(tft.width()/2 - RADIUS, 0); // Plot sprite
+
+  angle+=3;                   //Increment angle to rotate circle positions
+  if (angle > 359) angle = 0; // Limit angle range
+
+  // Slow things down
+  delay(WAIT);
+}
+// -------------------------------------------------------------------------
+
+
+// =========================================================================
+// Draw circles for Yin and Yang - rotate positions to create symbol
+// =========================================================================
+// x,y == coordinate center within Sprite
+// start_angle = 0 - 359
+// r = radius
+
+void yinyang(int x, int y, int start_angle, int r)
+{
+  int x1 = 0; // getCoord() will update these
+  int y1 = 0;
+
+  getCoord(x, y, &x1, &y1, r/2, start_angle); // Get x1 ,y1
+  img.fillCircle( x1,  y1, r/2, TFT_WHITE);
+  img.fillCircle( x1,  y1, r/8, TFT_BLACK);
+
+  getCoord(x, y, &x1, &y1, r/2, start_angle + 180);
+  img.fillCircle( x1,  y1, r/2, TFT_BLACK);
+  img.fillCircle( x1,  y1, r/8, TFT_WHITE);
+  
+  img.drawCircle(x, y, r, TFT_WHITE);
+}
+
+// =========================================================================
+// Get coordinates of end of a vector, pivot at x,y, length r, angle a
+// =========================================================================
+// Coordinates are returned to caller via the xp and yp pointers
+#define RAD2DEG 0.0174532925
+void getCoord(int x, int y, int *xp, int *yp, int r, int a)
+{
+  float sx1 = cos( (a-90) * RAD2DEG );    
+  float sy1 = sin( (a-90) * RAD2DEG );
+  *xp =  sx1 * r + x;
+  *yp =  sy1 * r + y;
+}
+