Fix 3.5C board support per CYD_PROJECT_GUIDE: BL=27, GT911 INT separate.

Correct ST7796/cyd_35r backlight, leave INT as input after reset, export firmware/cyd_35r.

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

include/pins.h

@@ -1,6 +1,7 @@
 #pragma once
 
 // Board pins — 2.8" default; 3.5" when CYD_BOARD_3248S035 is set (env:cyd_35r)
+// See ../CYD_PROJECT_GUIDE.md §A
 
 #if defined(CYD_BOARD_3248S035)
 #define TFT_BL_PIN 27
@@ -8,19 +9,27 @@
 #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.
+ * BL=27; INT=21 (not shared with BL). Touch-btn OUT stays GPIO22. */
+#define CYD_GT911_SDA  33
+#define CYD_GT911_SCL  32
+#define CYD_GT911_INT  21
+#define CYD_GT911_RST  25
+#define CYD_TFT_CS     15
 #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: SoftSPI touch. BL=21; touch-btn OUT GPIO22. */
 #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
+#define CYD_TFT_CS     15
+#endif
 
 /* Map 320x240 design coordinates onto the active UI resolution (identity on 2.8"). */
 #define UX(x) ((int)(((long)(x) * (UI_HOR_RES)) / 320))
@@ -28,5 +37,12 @@
 #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
 
+/* Primary peripheral pin — same on 2.8 and 3.5 */
 #define BTN_PIN 22