diff --git a/README.md b/README.md
index 6d368ed..8976d2f 100644
--- a/README.md
+++ b/README.md
@@ -28,7 +28,8 @@ ESP32 Cheap Yellow Display + INMP441（I2S）+ LVGL 声级仪表盘（近似 dB
 | SCK | IO27（2.8）/ IO21（3.5） |
 | SD | IO35（P3） |
 
-> 不要接 5V；不要占用背光脚。I2S 需要三根信号线，仅 IO22+IO27 不够。
+> 不要接 5V；不要占用背光脚。I2S 需要三根信号线，仅两根扩展脚不够（还要 P3 的 IO35）。  
+> **3.5C**：`SCK=GPIO21` 与 GT911 INT 同脚；固件先完成触控选址，再把 21 交给 I2S，触控仅轮询。背光是 **27**，勿当 SCK。
 
 ## 功能
 
@@ -95,6 +96,7 @@ README.md
 
 | 日期 | 说明 |
 |------|------|
+| 2026-10-27 | 兼容 3.5C（`cyd_35r`）：WS22/SCK21/SD35、BL27、GT911 Wire1 轮询；导出 `firmware/cyd_35r` |
 | 2026-10-27 | 文档补充实测读数：安静约 55–60、说话/拍手 70+；说明为相对声级、绝对未标定 |
 | 2026-10-27 | 修复无声贝变化：I2S 改立体声读槽（ESP32 L/R 与麦脚常反相）+ 去直流后再算 RMS |
 | 2026-10-27 | 初版：INMP441 I2S 声贝仪表盘（WS22/SCK27/SD35），LVGL 圆弧 + peak/min/max + 趋势图 |
diff --git a/firmware/cyd_35r/VERSION.txt b/firmware/cyd_35r/VERSION.txt
new file mode 100644
index 0000000..4b7d2c3
--- /dev/null
+++ b/firmware/cyd_35r/VERSION.txt
@@ -0,0 +1,17 @@
+name: CYD inmp441test (cyd_35r)
+git: 78658e3
+date: 2026-10-27
+board: ESP32-3248S035 (ST7796 + GT911)
+inmp441: WS=GPIO22 SCK=GPIO21 SD=GPIO35
+tft_bl: GPIO27
+flash_size: 4MB
+offsets:
+  0x1000  bootloader.bin
+  0x8000  partitions.bin
+  0xe000  boot_app0.bin
+  0x10000 firmware.bin
+sha256:
+  bootloader.bin  3D234A7471F67B013686DABD4DEE7C1FA915C9928463616A94BC9297ACF1ABF8
+  boot_app0.bin   F94C5D786A7A8FAB06AC5D10E33BF37711A6697636DC037559EA19CC410A17F0
+  firmware.bin    54A9F577980859E69E06F28982A632245AB3D67C99893C8B6996C510E25DC205
+  partitions.bin  0A8B5720E7B77FF11F1462458C3A509DEE79224E5279898F26D6A2E3AE0517B7
diff --git a/firmware/cyd_35r/boot_app0.bin b/firmware/cyd_35r/boot_app0.bin
new file mode 100644
index 0000000..13562ca
Binary files /dev/null and b/firmware/cyd_35r/boot_app0.bin differ
diff --git a/firmware/cyd_35r/bootloader.bin b/firmware/cyd_35r/bootloader.bin
new file mode 100644
index 0000000..d592359
Binary files /dev/null and b/firmware/cyd_35r/bootloader.bin differ
diff --git a/firmware/cyd_35r/firmware.bin b/firmware/cyd_35r/firmware.bin
new file mode 100644
index 0000000..5122dbc
Binary files /dev/null and b/firmware/cyd_35r/firmware.bin differ
diff --git a/firmware/cyd_35r/flash.ps1 b/firmware/cyd_35r/flash.ps1
index a586008..c2521b3 100644
--- a/firmware/cyd_35r/flash.ps1
+++ b/firmware/cyd_35r/flash.ps1
@@ -1,4 +1,4 @@
-# Flash archived CYD SGP30 firmware (no rebuild needed)
+# Flash archived CYD INMP441 sound-meter firmware for 3.5C (no rebuild needed)
 # Usage:
 #   .\flash.ps1
 #   .\flash.ps1 -Port COM5
diff --git a/firmware/cyd_35r/partitions.bin b/firmware/cyd_35r/partitions.bin
new file mode 100644
index 0000000..21800fa
Binary files /dev/null and b/firmware/cyd_35r/partitions.bin differ
diff --git a/src/main.cpp b/src/main.cpp
index f573ba7..9a5db5b 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -591,10 +591,14 @@ void setup() {
                 lv_version_major(), lv_version_minor(), lv_version_patch(),
                 I2S_WS_PIN, I2S_SCK_PIN, I2S_SD_PIN, TFT_BL_PIN);
 
+  /* 3.5: GT911 may pulse INT(=21) during addr select; release before I2S SCK. */
   touch_init();
 
   bool ok = mic_init();
   Serial.println(ok ? "I2S mic OK" : "I2S mic FAIL — check wiring");
+#if defined(CYD_BOARD_3248S035)
+  Serial.println("3.5C: SCK=GPIO21 (shared GT911 INT; touch is poll-only)");
+#endif
 
   lv_init();
 
diff --git a/src/touch.cpp b/src/touch.cpp
index fec313a..542862a 100644
--- a/src/touch.cpp
+++ b/src/touch.cpp
@@ -6,7 +6,9 @@
  * 2.8": XPT2046 resistive SoftSPI bus (CS33).
  * 3.5C (3248S035C): GT911 capacitive on Wire1 SDA33/SCL32/INT21/RST25.
  * Feed coords are always native panel 320x480 for LVGL ROTATION_270.
- * Wire1 leaves Wire free for SGP30 (3.5: SDA22/SCL21; TFT_BL=27).
+ * Wire1 keeps GT911 off the INMP441 pins (WS22 / SCK21). After touch_init(),
+ * main claims GPIO21 as I2S BCK — touch stays poll-only (no INT IRQ).
+ * TFT_BL=27 on 3.5C.
  */
 
 static int16_t clampi(int32_t v, int32_t lo, int32_t hi) {
@@ -76,7 +78,7 @@ static void gt_hw_reset(bool addr_0x14) {
   delay(5);
   digitalWrite(CYD_GT911_INT, LOW);
   delay(50);
-  /* Backlight is GPIO27 — release INT(21) as input (may share SCL for SGP30). */
+  /* BL=27. Release INT(21) before main reuses it as INMP441 I2S SCK. */
   pinMode(CYD_GT911_INT, INPUT);
   delay(50);
 }