Fix 3.5 CYD: backlight GPIO27, LCD SCL 21 via Wire1, GT911 INT as input.

Align cyd_35r with CYD_PROJECT_GUIDE so ST7796 is not black-screened, LCD does not steal GT911 Wire, and firmware/docs match 22+21 wiring.

Co-authored-by: Cursor <cursoragent@cursor.com>

include/pins.h

@@ -8,19 +8,25 @@
 #define SCREEN_HEIGHT 480
 #define UI_HOR_RES    480
 #define UI_VER_RES    320
+/* 3.5C capacitive GT911 (ESP32-3248S035C). GPIO33 is I2C SDA, not TOUCH_CS.
+ * Backlight is GPIO27; INT is GPIO21 — they are NOT the same pin. */
+#define CYD_GT911_SDA  33
+#define CYD_GT911_SCL  32
+#define CYD_GT911_INT  21
+#define CYD_GT911_RST  25
 #else
 #define TFT_BL_PIN 21
 #define SCREEN_WIDTH  240
 #define SCREEN_HEIGHT 320
 #define UI_HOR_RES    320
 #define UI_VER_RES    240
-#endif
-
+/* 2.8" CYD: dedicated SoftSPI touch bus. */
 #define CYD_TOUCH_IRQ  36
 #define CYD_TOUCH_MOSI 32
 #define CYD_TOUCH_MISO 39
 #define CYD_TOUCH_CLK  25
 #define CYD_TOUCH_CS   33
+#endif
 
 /* Map 320x240 design coordinates onto the active UI resolution (identity on 2.8"). */
 #define UX(x) ((int)(((long)(x) * (UI_HOR_RES)) / 320))
@@ -28,9 +34,20 @@
 #define UW(w) UX(w)
 #define UH(h) UY(h)
 
+/* Partial frame buffer: 3.5 needs smaller ratio to fit DRAM. */
+#if defined(CYD_BOARD_3248S035)
+#define DRAW_BUF_DIV 20
+#else
+#define DRAW_BUF_DIV 10
+#endif
 
+/* LCD1602A I2C backpack: 2.8 forever 22+27; 3.5 forever 22+21 (27 is BL). */
 #define LCD_I2C_SDA_PIN 22
+#if defined(CYD_BOARD_3248S035)
+#define LCD_I2C_SCL_PIN 21
+#else
 #define LCD_I2C_SCL_PIN 27
+#endif
 #define LCD_I2C_FREQ_HZ 100000
 #define LCD_COLS 16
 #define LCD_ROWS 2