feat(ui-lvgl): power saving, review fixes, shared helpers

Power: the UI loop sleeps until something is due (never with packets
queued); screen off puts the CPU at 80 MHz, the GT911 to sleep (unless a
tap wakes the screen) and the LP5814 in standby. GPS off now cuts the
L76K's rail and UART on the L2 (L2GpsProvider). The battery divider is
powered only for a reading (measured: settles at once); readings within
2 s are reused. The SD mount is retried at most every 5 s.

Fixes: WiFi left on after leaving a scan, live tiles' WiFi kept with the
screen off on the map, an ADC read every second for the status bar, touch
polled on every pass while dark, a scan cutting an update's WiFi, relay
count not refreshing in a channel thread, raw @[nick] in room previews.
Labels skip unchanged text (no redraw).

Helpers: scrollList, dimOverlay, settingRow, flexBox, nvs::get/put,
trailFilePath (a second save in the same minute no longer overwrites),
unreadTotal. Dead code removed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

variants/wio-tracker-l2/WioTrackerL2Board.cpp

@@ -14,6 +14,11 @@ static const uint8_t ADS_REG_CONFIG     = 0x01;
 static const uint16_t ADS_CFG_BATT = 0x8000 | 0x4000 | 0x0200 | 0x0100 | 0x0080 | 0x0003;
 // +/-4.096V FSR -> 125uV/LSB; battery is behind a x2 divider -> 0.25 mV/LSB
 static const float ADS_MV_PER_LSB = 0.125f * 2.0f;
+static const uint32_t BATT_SETTLE_MS = 1;       // divider on -> input settled (measured: at once)
+static const uint32_t BATT_REUSE_MS  = 2000;    // the UI, diagnostics and the app all ask
+
+// GT911: its command register; 0x05 = sleep
+static const uint8_t GT911_ADDR = 0x5D;
 
 bool WioTrackerL2Board::expWriteReg(uint8_t reg, uint8_t val) {
   Wire.beginTransmission(TCA9535_ADDR);
@@ -64,7 +69,7 @@ bool WioTrackerL2Board::initExpander() {
   delay(10);
   expSetOutput(EXP_PIN_TF_EN, HIGH);
   delay(10);
-  expSetOutput(EXP_PIN_BAT_ADC_EN, HIGH);
+  expSetOutput(EXP_PIN_BAT_ADC_EN, LOW);   // the divider only draws while a reading is taken
   delay(10);
   expSetOutput(EXP_PIN_GNSS_EN, HIGH);
   delay(10);
@@ -216,15 +221,40 @@ int16_t WioTrackerL2Board::adsReadRaw() {
 // A failed or zero ADS1115 read (the I2C bus busy or the ADC not answering)
 // keeps the last good value instead of reporting 0 mV -- that read as 0 % in
 // the status bar and could trip the low-battery shutdown. Retried once first.
+// The divider is powered only around the reading; one taken in the last 2 s
+// is reused.
 uint16_t WioTrackerL2Board::getBattMilliVolts() {
   if (!expander_ok) return 0;  // BAT_ADC_EN rail never came up
+  if (batt_mv_last && millis() - batt_read_ms < BATT_REUSE_MS) return batt_mv_last;
 
+  expWritePin(EXP_PIN_BAT_ADC_EN, HIGH);
+  delay(BATT_SETTLE_MS);
   for (int attempt = 0; attempt < 2; attempt++) {
     int16_t raw = adsReadRaw();
     if (raw > 0) {
       batt_mv_last = (uint16_t)(raw * ADS_MV_PER_LSB);
-      return batt_mv_last;
+      break;
     }
   }
+  expWritePin(EXP_PIN_BAT_ADC_EN, LOW);
+  batt_read_ms = millis();
   return batt_mv_last;
 }
+
+void WioTrackerL2Board::touchSleep() {
+  if (!expander_ok) return;
+  expWritePin(EXP_PIN_TP_INT, LOW);   // held low while it sleeps (it is, from the reset sequence on)
+  Wire.beginTransmission(GT911_ADDR);
+  Wire.write((uint8_t)0x80);
+  Wire.write((uint8_t)0x40);
+  Wire.write((uint8_t)0x05);
+  Wire.endTransmission();
+}
+
+void WioTrackerL2Board::touchWake() {
+  if (!expander_ok) return;
+  expWritePin(EXP_PIN_TP_INT, HIGH);   // 2-5 ms high wakes it
+  delay(5);
+  expWritePin(EXP_PIN_TP_INT, LOW);
+}
+

variants/wio-tracker-l2/WioTrackerL2Board.h

@@ -20,7 +20,7 @@
 #define ADS1115_ADDR   0x48
 
 // TCA9535 pin numbering: 0..7 = port 0 (P00..P07), 8..15 = port 1 (P10..P17)
-#define EXP_PIN_WAKE_BTN     0   // input  - side WAKE button
+#define EXP_PIN_WAKE_BTN     0   // input  - WAKE button (top edge)
 #define EXP_PIN_I2C_IRQ      1   // input  - shared I2C IRQ
 #define EXP_PIN_SD_DETECT    2   // input  - microSD card detect
 #define EXP_PIN_TP_INT       3   // output - touch panel interrupt (driven for reset seq)
@@ -57,8 +57,6 @@ public:
   // antenna away from class-D switching noise and to save battery
   void setSpeakerAmp(bool on) { expWritePin(EXP_PIN_PA_EN, on); }
 
-  // hardware reset pulse to the L76K GNSS (active HIGH on this board); the
-  // module keeps almanac/ephemeris across it, so this is a warm restart
   // GNSS rail: off saves the whole receiver when GPS is disabled; on re-runs
   // the power-up reset so the module comes back cleanly
   void setGnssPower(bool on) {
@@ -73,6 +71,10 @@ public:
   // Grove expansion port rail (nothing on-board depends on it)
   void setGrovePower(bool on) { expWritePin(EXP_PIN_GROVE_EN, on); }
 
+  bool gnssPowered() const { return (out_shadow[EXP_PIN_GNSS_EN >> 3] >> (EXP_PIN_GNSS_EN & 7)) & 1; }
+
+  // hardware reset pulse to the L76K GNSS (active HIGH on this board); the
+  // module keeps almanac/ephemeris across it, so this is a warm restart
   void gnssReset() {
     expWritePin(EXP_PIN_GNSS_RST, HIGH);
     delay(10);
@@ -82,6 +84,11 @@ public:
   // WAKE button on expander P00: pressed = level differs from boot baseline
   bool readWakeButton();
 
+  // GT911 touch controller: sleep (a few mA -> tens of uA) while the screen is
+  // off and a touch shouldn't wake it; wake with a pulse on its INT line.
+  void touchSleep();
+  void touchWake();
+
   // VBUS presence via the AW35615 USB-C controller (I2C 0x22)
   bool isExternalPowered() override;
   int awRead(uint8_t reg);   // AW35615 register, -1 on error
@@ -95,6 +102,7 @@ private:
   bool aw_ok = false;              // AW35615 USB-C controller responded at probe
   uint8_t wake_btn_baseline = 0;   // idle level of P00, captured at init
   uint16_t batt_mv_last = 0;       // last good battery reading (a failed read keeps it)
+  uint32_t batt_read_ms = 0;       // when it was taken (reads closer together reuse it)
 
   int expReadInputs();   // 16-bit input register pair, -1 on error
 

variants/wio-tracker-l2/WioTrackerL2Display.h

@@ -33,6 +33,7 @@ class WioTrackerL2Backlight : public lgfx::v1::ILight {
   static constexpr uint8_t REG_LED0_PWM = 0x18;
 
   uint8_t _brightness = 153;  // 60%
+  bool _standby = false;      // chip disabled (the screen is off)
 
   void writeReg(uint8_t reg, uint8_t value) {
     Wire.beginTransmission(LP5814_I2C_ADDR);
@@ -41,13 +42,7 @@ class WioTrackerL2Backlight : public lgfx::v1::ILight {
     Wire.endTransmission();
   }
 
-public:
-  bool init(uint8_t brightness) override {
-    Wire.beginTransmission(LP5814_I2C_ADDR);
-    if (Wire.endTransmission() != 0) {
-      return false;  // LP5814 not found
-    }
-
+  void configure() {
     writeReg(REG_DEVICE_CONFIG0, 0x01);  // chip enable
     writeReg(REG_MAX_CURRENT, 0x01);     // 51 mA max current
     writeReg(REG_ENABLE_CONTROL, 0x00);  // outputs off while configuring
@@ -59,12 +54,28 @@ public:
     writeReg(REG_ENABLE_CONTROL, 0x0F);  // enable all 4 channels
     writeReg(REG_UPDATE, 0x55);          // latch (LP5814 requires 0x55)
     delay(5);
+  }
 
+public:
+  bool init(uint8_t brightness) override {
+    Wire.beginTransmission(LP5814_I2C_ADDR);
+    if (Wire.endTransmission() != 0) {
+      return false;  // LP5814 not found
+    }
+    configure();
     setBrightness(brightness);
     return true;
   }
 
+  // 0 (LovyanGFX's sleep()) puts the chip in standby; the next level brings it
+  // back, set up again.
   void setBrightness(uint8_t brightness) override {
+    if (brightness == 0) {
+      writeReg(REG_DEVICE_CONFIG0, 0x00);   // chip disable: standby
+      _standby = true;
+      return;
+    }
+    if (_standby) { configure(); _standby = false; }
     for (uint8_t i = 0; i < 4; i++) {
       writeReg(REG_LED0_PWM + i, brightness);
     }

variants/wio-tracker-l2/target.cpp

@@ -10,7 +10,7 @@ WRAPPER_CLASS radio_driver(radio, board);
 
 ESP32RTCClock fallback_clock;
 AutoDiscoverRTCClock rtc_clock(fallback_clock);
-MicroNMEALocationProvider gps(Serial1, &rtc_clock);
+L2GpsProvider gps(Serial1, &rtc_clock);
 EnvironmentSensorManager sensors(gps);
 
 #ifdef DISPLAY_CLASS
@@ -22,6 +22,28 @@ EnvironmentSensorManager sensors(gps);
 void buzzerAmpPower(bool on) { board.setSpeakerAmp(on); }
 #endif
 
+void L2GpsProvider::begin() {
+  board.setGnssPower(true);   // with the power-up reset
+  if (_uart_off) {            // back from stop(): the UART again
+    Serial1.setRxBufferSize(1024);
+    Serial1.begin(GPS_BAUD_RATE, SERIAL_8N1, PIN_GPS_TX, PIN_GPS_RX);
+    _uart_off = false;
+  }
+  MicroNMEALocationProvider::begin();
+}
+
+void L2GpsProvider::stop() {
+  MicroNMEALocationProvider::stop();
+  // The UART's TX idling high would feed the unpowered module through its pin.
+  Serial1.end();
+  pinMode(PIN_GPS_RX, INPUT);   // PIN_GPS_RX: the module's RX, our TX
+  _uart_off = true;
+  board.setGnssPower(false);
+}
+
+void L2GpsProvider::reset() { board.gnssReset(); }
+bool L2GpsProvider::isEnabled() { return board.gnssPowered(); }
+
 bool radio_init() {
   MESH_DEBUG_PRINTLN("radio_init: rtc + sx1262 init");
   fallback_clock.begin();

variants/wio-tracker-l2/target.h

@@ -14,11 +14,24 @@
   #include <helpers/ui/MomentaryButton.h>
 #endif
 
+// The L76K's power and reset lines are on the IO expander, out of the NMEA
+// provider's reach: begin() / stop() / reset() drive them here, so GPS off
+// (Settings, duty cycling) really powers the receiver down.
+class L2GpsProvider : public MicroNMEALocationProvider {
+  bool _uart_off = false;
+public:
+  using MicroNMEALocationProvider::MicroNMEALocationProvider;
+  void begin() override;
+  void stop() override;
+  void reset() override;
+  bool isEnabled() override;
+};
+
 extern WioTrackerL2Board board;
 extern WRAPPER_CLASS radio_driver;
 extern AutoDiscoverRTCClock rtc_clock;
 extern EnvironmentSensorManager sensors;
-extern MicroNMEALocationProvider gps;
+extern L2GpsProvider gps;
 
 #ifdef DISPLAY_CLASS
   extern DISPLAY_CLASS display;