implementing low battery brownout protection to prevent contacts file corruption caused by low voltage reboot loop; board goes to sleep at 2800mv

examples/companion_radio/DataStore.cpp

@@ -303,6 +303,38 @@ void DataStore::loadContacts(DataStoreHost* host) {
 
   File file = openRead(fs, "/contacts3");
     if (file) {
+      // --- Truncation guard ---
+      // If the file is smaller than one full contact record (152 bytes),
+      // it was truncated by a crash/brown-out. Discard it and try the
+      // .tmp backup if available.
+      size_t fsize = file.size();
+      if (fsize > 0 && fsize < 152) {
+        Serial.printf("DataStore: contacts3 truncated (%d bytes < 152), discarding\n", (int)fsize);
+        file.close();
+        fs->remove("/contacts3");
+        if (fs->exists("/contacts3.tmp")) {
+          File tmp = openRead(fs, "/contacts3.tmp");
+          if (tmp && tmp.size() >= 152) {
+            Serial.println("DataStore: recovering from .tmp after truncation");
+            tmp.close();
+            fs->rename("/contacts3.tmp", "/contacts3");
+            file = openRead(fs, "/contacts3");
+            if (!file) return;  // give up
+          } else {
+            if (tmp) tmp.close();
+            Serial.println("DataStore: no valid contacts backup — starting fresh");
+            return;
+          }
+        } else {
+          Serial.println("DataStore: no .tmp backup — starting fresh");
+          return;
+        }
+      } else if (fsize == 0) {
+        // Empty file — nothing to load
+        file.close();
+        return;
+      }
+
       bool full = false;
       while (!full) {
         ContactInfo c;

examples/companion_radio/ui-new/UITask.cpp

@@ -1289,10 +1289,11 @@ if (curr) curr->poll();
   if (millis() > next_batt_chck) {
     uint16_t milliVolts = getBattMilliVolts();
     if (milliVolts > 0 && milliVolts < AUTO_SHUTDOWN_MILLIVOLTS) {
+      _low_batt_count++;
+      if (_low_batt_count >= 3) {  // 3 consecutive low readings (~24s) to avoid transient sags
 
-      // show low battery shutdown alert
-      // we should only do this for eink displays, which will persist after power loss
-      #if defined(THINKNODE_M1) || defined(LILYGO_TECHO)
+      // show low battery shutdown alert on e-ink (persists after power loss)
+      #if defined(THINKNODE_M1) || defined(LILYGO_TECHO) || defined(LilyGo_TDeck_Pro)
       if (_display != NULL) {
         _display->startFrame();
         _display->setTextSize(2);
@@ -1304,7 +1305,9 @@ if (curr) curr->poll();
       #endif
 
       shutdown();
-
+      }
+    } else {
+      _low_batt_count = 0;
     }
     next_batt_chck = millis() + 8000;
   }

examples/companion_radio/ui-new/UITask.h

@@ -54,6 +54,7 @@ class UITask : public AbstractUITask {
   unsigned long _alert_expiry;
   int _msgcount;
   unsigned long ui_started_at, next_batt_chck;
+  uint8_t _low_batt_count = 0;  // Consecutive low-voltage readings for debounce
   int next_backlight_btn_check = 0;
 #ifdef PIN_STATUS_LED
   int led_state = 0;

variants/lilygo_tdeck_pro/TDeckBoard.cpp

@@ -78,6 +78,25 @@ void TDeckBoard::begin() {
     MESH_DEBUG_PRINTLN("TDeckBoard::begin() - Battery voltage: %d mV", voltage);
     configureFuelGauge();
   #endif
+
+  // --- Early low-voltage protection ---
+  // If we boot below the shutdown threshold, go straight to deep sleep
+  // WITHOUT touching the filesystem. This breaks the brown-out reboot
+  // loop that corrupts contacts when battery is deeply depleted (~2.5V).
+  #if HAS_BQ27220 && defined(AUTO_SHUTDOWN_MILLIVOLTS)
+  {
+    uint16_t bootMv = getBattMilliVolts();
+    if (bootMv > 0 && bootMv < AUTO_SHUTDOWN_MILLIVOLTS) {
+      Serial.printf("CRITICAL: Boot voltage %dmV < %dmV — sleeping immediately\n",
+                    bootMv, AUTO_SHUTDOWN_MILLIVOLTS);
+      // Don't mount SD, don't load contacts, don't pass Go.
+      // Only wake on user button press (presumably after plugging in charger).
+      esp_sleep_disable_wakeup_source(ESP_SLEEP_WAKEUP_ALL);
+      esp_sleep_enable_ext1_wakeup(1ULL << PIN_USER_BTN, ESP_EXT1_WAKEUP_ANY_HIGH);
+      esp_deep_sleep_start();  // CPU halts here
+    }
+  }
+  #endif
   
   MESH_DEBUG_PRINTLN("TDeckBoard::begin() - complete");
 }

variants/lilygo_tdeck_pro/platformio.ini

@@ -62,6 +62,8 @@ build_flags =
   -D EINK_MOSI=33
   -D EINK_BL=45
   -D EINK_NOT_HIBERNATE=1
+  -D HAS_BQ27220=1
+  -D AUTO_SHUTDOWN_MILLIVOLTS=2800
   -D EINK_LIMIT_FASTREFRESH=10
   -D EINK_LIMIT_GHOSTING_PX=2000
   -D DISPLAY_ROTATION=0