From a8b3fc5ce3fdca7fad0aa809d4aefe4feb1197ab Mon Sep 17 00:00:00 2001
From: Nick Dunklee <nick@dunklee.org>
Date: Mon, 16 Mar 2026 22:15:10 -0600
Subject: [PATCH] fix(t1000-e): fix extended uptime failures in GPS and sensor
 code - Fix millis() wraparound (49-day) in T1000SensorManager::loop() and  
 MicroNMEALocationProvider::loop() by switching from absolute comparison  
 (millis() > next_*) to elapsed-time arithmetic ((uint32_t)(millis() - last_*)
 >= interval)   with uint32_t timestamps; previous pattern could stall GPS
 updates and   time sync for up to ~24 days after wraparound - Fix
 division-by-zero crash in get_heater_temperature() when ntc_volt == 0   (open
 circuit or bad ADC read); now returns 0.0f safely - Fix out-of-bounds array
 access in get_heater_temperature(): loop exit at   i == 0 caused
 ntc_res2[i-1] / ntc_temp2[i-1] at index -1; loop exhaustion   at i == 136
 caused ntc_res2[136] one-past-end read; clamped i to [1, 135]   with
 early-exit returns for edge temperatures and guarded interpolation  
 denominator against zero

---
 .../sensors/MicroNMEALocationProvider.h       |  6 +++---
 variants/t1000-e/t1000e_sensors.cpp           | 21 ++++++++++++++-----
 variants/t1000-e/target.cpp                   |  8 +++----
 3 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/src/helpers/sensors/MicroNMEALocationProvider.h b/src/helpers/sensors/MicroNMEALocationProvider.h
index 1de7532758..e4f9286186 100644
--- a/src/helpers/sensors/MicroNMEALocationProvider.h
+++ b/src/helpers/sensors/MicroNMEALocationProvider.h
@@ -41,7 +41,7 @@ class MicroNMEALocationProvider : public LocationProvider {
     RefCountedDigitalPin* _peripher_power;
     int _pin_reset;
     int _pin_en;
-    long next_check = 0;
+    uint32_t last_check = 0;
     long time_valid = 0;
 
 public :
@@ -127,8 +127,8 @@ public :
 
         if (!isValid()) time_valid = 0;
 
-        if (millis() > next_check) {
-            next_check = millis() + 1000;
+        if ((uint32_t)(millis() - last_check) >= 1000) {
+            last_check = millis();
             if (_time_sync_needed && time_valid > 2) {
                 if (_clock != NULL) {
                     _clock->setCurrentTime(getTimestamp());
diff --git a/variants/t1000-e/t1000e_sensors.cpp b/variants/t1000-e/t1000e_sensors.cpp
index f02541382d..7bfa06f05d 100644
--- a/variants/t1000-e/t1000e_sensors.cpp
+++ b/variants/t1000-e/t1000e_sensors.cpp
@@ -32,11 +32,12 @@ static char ntc_temp2[136] = {
 };
 
 static float get_heater_temperature(unsigned int vcc_volt, unsigned int ntc_volt) {
+  if (ntc_volt == 0) {
+    return 0.0f;  // avoid division by zero on open circuit / sensor fault
+  }
   int i = 0;
-  float Vout = 0, Rt = 0, temp = 0;
-  Vout = ntc_volt;
-
-  Rt = (HEATER_NTC_RP * vcc_volt) / Vout - HEATER_NTC_RP;
+  float Rt = 0, temp = 0;
+  Rt = (HEATER_NTC_RP * (float)vcc_volt) / ntc_volt - HEATER_NTC_RP;
 
   for (i = 0; i < 136; i++) {
     if (Rt >= ntc_res2[i]) {
@@ -44,7 +45,17 @@ static float get_heater_temperature(unsigned int vcc_volt, unsigned int ntc_volt
     }
   }
 
-  temp = ntc_temp2[i - 1] + 1 * (ntc_res2[i - 1] - Rt) / (float)(ntc_res2[i - 1] - ntc_res2[i]);
+  if (i <= 0) {
+    return (float)ntc_temp2[0];
+  }
+  if (i >= 136) {
+    return (float)ntc_temp2[135];
+  }
+  int denom = ntc_res2[i - 1] - ntc_res2[i];
+  if (denom == 0) {
+    return (float)ntc_temp2[i - 1];
+  }
+  temp = ntc_temp2[i - 1] + 1 * (ntc_res2[i - 1] - Rt) / (float)denom;
 
   temp = (temp * 100 + 5) / 100;
   return temp;
diff --git a/variants/t1000-e/target.cpp b/variants/t1000-e/target.cpp
index da8fa48bb3..30395bb717 100644
--- a/variants/t1000-e/target.cpp
+++ b/variants/t1000-e/target.cpp
@@ -162,18 +162,18 @@ bool T1000SensorManager::querySensors(uint8_t requester_permissions, CayenneLPP&
 }
 
 void T1000SensorManager::loop() {
-  static long next_gps_update = 0;
+  static uint32_t last_gps_update = 0;
+  constexpr uint32_t GPS_UPDATE_INTERVAL_MS = 1000;
 
   _nmea->loop();
 
-  if (millis() > next_gps_update) {
+  if ((uint32_t)(millis() - last_gps_update) >= GPS_UPDATE_INTERVAL_MS) {
     if (gps_active && _nmea->isValid()) {
       node_lat = ((double)_nmea->getLatitude())/1000000.;
       node_lon = ((double)_nmea->getLongitude())/1000000.;
       node_altitude = ((double)_nmea->getAltitude()) / 1000.0;
-      //Serial.printf("lat %f lon %f\r\n", _lat, _lon);
     }
-    next_gps_update = millis() + 1000;
+    last_gps_update = millis();
   }
 }