tune(touch): RTC を 2→5 に拡大 + サーボ電源 ON 後に recalibrate()

m5stack/StackChan-BSP#6 で提案された残り 2 つの対策を導入。

1. CTRL1 の RTC[2:0] を 2 → 5 に拡大。応答サイクルが 4 → 7 になり、
   software 側の firmly_touched() フィルタに加えて HW debounce が
   1 段乗る。radio coex バースト 1 発で抜けてくる単発スパイクを
   弾く目的。なで検出のレイテンシは ~30 ms 程度しか増えない。
2. Si12tTouch::recalibrate() を追加し、サーボ VM 電源 ON + 1.5 s
   settle 後に呼び出して baseline を再取得。サーボ電源が立ち上がる
   と内部電源環境が変わって以前の baseline が外れたまま FTC=10 s の
   slow auto-cal を待つことになり、その間 ghost touch が出る原因。

実機で「感度を Type_Low/L3 に下げても誤爆がまだ起きる」状態だったので
合わせ技で対策。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: ciniml

components/board/include/board/si12t_touch.hpp

@@ -65,6 +65,13 @@ class Si12tTouch {
     // intensities. Returns an all-zero Reading on bus error.
     Reading read();
 
+    // Force the chip to update its idle baseline for all channels. Call
+    // after a disturbance that's likely to skew the running baseline (e.g.
+    // servo VM rail switched on, Wi-Fi associated). Without this the chip
+    // can park its baseline mid-burst and report ghost touches until its
+    // own slow auto-calibration catches up (FTC = 10 s).
+    void recalibrate();
+
     std::uint8_t address() const noexcept { return address_; }
 
 private:

components/board/si12t_touch.cpp

@@ -45,8 +45,15 @@ constexpr std::uint8_t kRegOutput1 = 0x10;
 //     firmware (hal_head_touch.cpp). m5stack/StackChan-BSP#6 trial.
 constexpr std::uint8_t kSensitivityValue = 0x33;
 
-// CTRL1 = Auto Mode, FTC=01, response interrupt on Middle/High.
-constexpr std::uint8_t kCtrl1Value = 0x22;
+// CTRL1 = MS | FTC[1:0] | ILC[1:0] | RTC[2:0].
+//   0x25 = auto mode, FTC=01 (10 s first-touch recal), ILC=00 (interrupt on
+//   middle/high), RTC=5 → response cycle (RTC + 2) = 7 scan cycles.
+//   Was 0x22 (RTC=2 → 4 cycles); bumping to 5 stacks an extra HW debounce
+//   on top of our software firmly_touched() filter to reject single-spike
+//   noise from radio coex bursts. Trade-off: nadenade latency rises by
+//   roughly (5-2) scan cycles ≈ 30 ms at the chip's default scan rate,
+//   which is unnoticeable for head-petting. m5stack/StackChan-BSP#6 trial.
+constexpr std::uint8_t kCtrl1Value = 0x25;
 
 } // namespace
 
@@ -91,6 +98,19 @@ tl::expected<Si12tTouch, Error> Si12tTouch::probe(std::uint8_t address)
     return chip;
 }
 
+void Si12tTouch::recalibrate()
+{
+    // Pulse all-channel bits in Ref_rst1 (ch 1-8) / Ref_rst2 (ch 9-12) to
+    // force the chip to update its idle baseline (datasheet 12.2.4). Call
+    // after known disturbances — power-rail switching, radio coex bursts —
+    // that would otherwise leave the baseline biased and the chip stuck
+    // reporting low-level intensities with nothing touching it.
+    write_register(kRegRefRst1, 0xFF);
+    write_register(kRegRefRst2, 0x0F);
+    write_register(kRegRefRst1, 0x00);
+    write_register(kRegRefRst2, 0x00);
+}
+
 Si12tTouch::Reading Si12tTouch::read()
 {
     Reading r{};

main/app_main.cpp

@@ -1121,6 +1121,15 @@ extern "C" void app_main()
         // driving UART. SCS0009 needs ~1 s after Vmotor comes up before it
         // answers PING.
         vTaskDelay(pdMS_TO_TICKS(1500));
+        // Servo VM coming up is a known Si12T baseline disturbance: the
+        // chip's running baseline acquired with Vmotor off no longer
+        // matches the post-power-on environment, which we've seen as
+        // ghost head-touch firings in the first few seconds. Force a
+        // baseline update now (cheap: 4 I2C writes) so the chip starts
+        // clean instead of waiting for FTC=10 s to drift back.
+        if (auto* t = board.touch_sensor(); t != nullptr) {
+            t->recalibrate();
+        }
     } else if (!cfg.servo_enabled) {
         ESP_LOGW(kTag, "servo VM rail OFF: cfg.servo_enabled=false (set via settings UI)");
     }