fix(wio-tracker-l2): USB power detection works - charge bolt, Power row, GPS hint

- The AW35615 USB-C controller (FUSB302-style registers, ID 0x91) only
  reports VBUSOK with its measure block on; POWER resets to bandgap only,
  so isExternalPowered() was always false. Board init turns it on
- Status bar shows a charge bolt on the cable, Diagnostics > Live has a
  Power row, the GPS screen notes that charging disturbs GPS, and the
  low-battery warning is skipped on USB as intended
- Roadmap: USB detection closed; GPS indoors still worse than the L1
  even on battery, left open for later

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

docs/development/l2-roadmap.md

@@ -196,13 +196,12 @@ this roadmap is done; the Cardputer follows whatever the spike shows.
 
 ## Backlog (found along the way)
 
-- [ ] USB power detection: `WioTrackerL2Board::isExternalPowered()` reads
-      STATUS0 (0x40) bit 7 of the chip at I2C 0x22 and always gets 0 with
-      USB plugged in (0x40 reads 0x01). Needed for a charging indicator and
-      for skipping the low-battery shutdown on the cable. Find the right
-      chip / register (devices on the bus: 0x14, 0x18, 0x21, 0x22, 0x2c,
-      0x34, 0x48, 0x5d). Found 2026-09-26. Also wanted for a hint on the
-      GPS screen while on the cable (see below).
+- [x] USB power detection (fixed 2026-09-26): the AW35615 at 0x22 has a
+      FUSB302-style register map (device ID 0x91); VBUSOK (STATUS0 bit 7)
+      needs the measure block on, and POWER (0x0B) resets to 0x01. Board
+      init sets PWR[1..2]; STATUS0 then reads 0x80 on USB. Used by the
+      status bar (charge bolt), Diagnostics > Live "Power", the GPS screen
+      hint and the low-battery warning (skipped on the cable).
 - [x] GPS screen (2026-09-26): Home > GPS and Settings > System > GPS
       details -- sky plot, C/N0 bar per satellite, fix / TTFF / DOPs,
       per-constellation counts (helpers/sensors/GpsSky.h, -D GPS_SKYVIEW;
@@ -214,6 +213,11 @@ this roadmap is done; the Cardputer follows whatever the spike shows.
       seconds, first fix after 377 s. Screen, WiFi, Bluetooth and LoRa TX
       were ruled out. Cause: noise from USB power / the charger -- a board
       property, not fixable in firmware. Test GPS on battery.
+- [ ] GPS indoors, still open (user, 2026-09-26): even on battery the L2
+      does worse than the L1 with the same L76K -- first fix after 377 s by
+      a window, 4 of 22 satellites used, the fix drops and comes back.
+      Something is still off (antenna / placement / another noise source);
+      look again later with the GPS screen, e.g. side by side with the L1.
 
 Ideas to come back to (2026-09-26):
 

examples/companion_radio/ui-lvgl/DiagScreen.h

@@ -10,7 +10,7 @@ namespace diagview {
 enum : uint8_t { TAB_LIVE, TAB_SYSTEM, TAB_FONT, TAB_COUNT };
 static uint8_t s_tab = TAB_LIVE;   // kept across visits
 static lv_obj_t* s_list = nullptr;
-static const int EXTRA = 3;   // GPS, last reset, last crash (L2 only)
+static const int EXTRA = 4;   // GPS, power, last reset, last crash (L2 only)
 static lv_obj_t* s_vals[diag::MAX_ROWS + EXTRA];
 static int s_rows = 0;
 
@@ -34,6 +34,7 @@ static int allRows(diag::Row* rows, bool gps_on) {
   if (!gps_on) extraRow(rows, n, "GPS", "off");
   else if (!data) extraRow(rows, n, "GPS", "no data (%lu B)", (unsigned long)c);
   else extraRow(rows, n, "GPS", "%s, %ld sats", gps.isValid() ? "fix" : "no fix", gps.satellitesCount());
+  extraRow(rows, n, "Power", "%s", board.isExternalPowered() ? "USB" : "battery");
 #else
   (void)gps_on;
 #endif

examples/companion_radio/ui-lvgl/GpsScreen.h

@@ -348,7 +348,7 @@ void UITask::refreshGps() {
   if (off) lv_obj_remove_flag(s_on_btn, LV_OBJ_FLAG_HIDDEN);
   else lv_obj_add_flag(s_on_btn, LV_OBJ_FLAG_HIDDEN);
 
-  char used[48] = "", info[200] = "";
+  char used[48] = "", info[240] = "";
   if (!g) {
     lv_label_set_text(s_status, "Not available");
     lv_obj_set_style_text_color(s_status, lv_color_hex(theme::TEXT_MUTED), 0);
@@ -387,6 +387,10 @@ void UITask::refreshGps() {
       o += snprintf(info + o, sizeof(info) - o, "%.0f m  -  %.1f km/h\n", g->alt_m, g->speed_kmh);
     if (g->utc_valid) o += snprintf(info + o, sizeof(info) - o, "UTC %02u:%02u:%02u", g->utc_h, g->utc_m, g->utc_s);
   }
+  if (g && !off && _board->isExternalPowered()) {   // measured: on the cable the L76K never decodes indoors
+    size_t o = strlen(info);
+    snprintf(info + o, sizeof(info) - o, "%sOn USB power: charging disturbs GPS", o ? "\n" : "");
+  }
   lv_label_set_text(s_used, used);
   lv_label_set_text(s_info, info);
 

examples/companion_radio/ui-lvgl/UITask.cpp

@@ -616,7 +616,7 @@ void UITask::refreshStatusBar() {
     case battery::VOLTAGE: snprintf(level, sizeof(level), " %u.%02u V", mv / 1000, (mv % 1000) / 10); break;
     default: break;
   }
-  lv_label_set_text_fmt(_status_batt, "%s%s", batt, level);
+  lv_label_set_text_fmt(_status_batt, "%s%s%s", _board->isExternalPowered() ? LV_SYMBOL_CHARGE " " : "", batt, level);
 
   // Status icons, as the original's status bar (ui-new): Bluetooth (bright
   // when the app is connected), GPS (green with a fix), the alarm, mute, then

variants/wio-tracker-l2/WioTrackerL2Board.cpp

@@ -125,6 +125,20 @@ void WioTrackerL2Board::begin() {
 
   Wire.beginTransmission(0x22);
   aw_ok = Wire.endTransmission() == 0;
+  if (aw_ok) {
+    // AW35615 = FUSB302-style register map. VBUSOK (STATUS0 bit 7) only
+    // works with the measure block powered: POWER (0x0B) resets to 0x01
+    // (bandgap only), which reads "no USB" forever. Add the receiver /
+    // current references and the measure block (PWR[1..2]).
+    // Verified on hardware: device ID 0x91; STATUS0 0x01 -> 0x80 on USB.
+    int pw = awRead(0x0B);
+    if (pw >= 0) {
+      Wire.beginTransmission(0x22);
+      Wire.write((uint8_t)0x0B);
+      Wire.write((uint8_t)(pw | 0x07));
+      Wire.endTransmission();
+    }
+  }
   MESH_DEBUG_PRINTLN("WioTrackerL2Board: init done");
 
   esp_reset_reason_t reason = esp_reset_reason();
@@ -156,13 +170,18 @@ int WioTrackerL2Board::expReadInputs() {
   return lo | (hi << 8);
 }
 
-bool WioTrackerL2Board::isExternalPowered() {
-  if (!aw_ok) return false;
+int WioTrackerL2Board::awRead(uint8_t reg) {
+  if (!aw_ok) return -1;
   Wire.beginTransmission(0x22);
-  Wire.write((uint8_t)0x40);   // STATUS0
-  if (Wire.endTransmission() != 0) return false;
-  if (Wire.requestFrom(0x22, 1) != 1) return false;
-  return (Wire.read() & 0x80) != 0;   // VBUSOK bit
+  Wire.write(reg);
+  if (Wire.endTransmission() != 0) return -1;
+  if (Wire.requestFrom(0x22, 1) != 1) return -1;
+  return Wire.read();
+}
+
+bool WioTrackerL2Board::isExternalPowered() {
+  int st0 = awRead(0x40);   // STATUS0
+  return st0 >= 0 && (st0 & 0x80) != 0;   // VBUSOK
 }
 
 bool WioTrackerL2Board::readWakeButton() {

variants/wio-tracker-l2/WioTrackerL2Board.h

@@ -84,6 +84,7 @@ public:
 
   // VBUS presence via the AW35615 USB-C controller (I2C 0x22)
   bool isExternalPowered() override;
+  int awRead(uint8_t reg);   // AW35615 register, -1 on error
 
   bool expanderOK() const { return expander_ok; }