From 9451cf1cfd88c8a04e80d9cd255ecb1db10a7766 Mon Sep 17 00:00:00 2001
From: Theo Arends <11044339+arendst@users.noreply.github.com>
Date: Mon, 5 Jan 2026 12:07:01 +0100
Subject: [PATCH] Add optional define LM75AD_SKIP_NULL_SENSOR

---
 .../tasmota_xsns_sensor/xsns_26_lm75ad.ino    | 38 ++++++++++---------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/tasmota/tasmota_xsns_sensor/xsns_26_lm75ad.ino b/tasmota/tasmota_xsns_sensor/xsns_26_lm75ad.ino
index 8f818ec70..0877fdd14 100644
--- a/tasmota/tasmota_xsns_sensor/xsns_26_lm75ad.ino
+++ b/tasmota/tasmota_xsns_sensor/xsns_26_lm75ad.ino
@@ -28,20 +28,22 @@
  * I2C Address: 0x48 - 0x4F
 \*********************************************************************************************/
 
-#define XSNS_26                 26
-#define XI2C_20                 20    // See I2CDEVICES.md
+#define XSNS_26                   26
+#define XI2C_20                   20    // See I2CDEVICES.md
 
 #ifndef LM75AD_MAX_SENSORS
-#define LM75AD_MAX_SENSORS      8
+#define LM75AD_MAX_SENSORS        8
 #endif
 
-#define LM75AD_ADDRESS          0x48  // Start address
-#define LM75AD_COUNT            8     // Number of sequential addresses
+//#define LM75AD_SKIP_NULL_SENSOR         // Skip sensor instead of reporting null value
 
-#define LM75_TEMP_REGISTER      0x00
-#define LM75_CONF_REGISTER      0x01
-#define LM75_THYST_REGISTER     0x02
-#define LM75_TOS_REGISTER       0x03
+#define LM75AD_ADDRESS            0x48  // Start address
+#define LM75AD_COUNT              8     // Number of sequential addresses
+
+#define LM75_TEMP_REGISTER        0x00
+#define LM75_CONF_REGISTER        0x01  // Power On State is 0x00
+#define LM75_THYST_REGISTER       0x02  // Power On state is 0x4B00 = 75C - Used for I2C device detection
+#define LM75_TOS_REGISTER         0x03  // Power On State is 0x5000 = 80C
 
 struct {
   uint8_t address[LM75AD_MAX_SENSORS];
@@ -53,7 +55,7 @@ void LM75ADDetect(void) {
   if ((LM75AD_MAX_SENSORS < 1) || (LM75AD_MAX_SENSORS > 16)) { return; }  // Safeguard user changed LM75AD_MAX_SENSORS out of bounds
   for (uint32_t bus = 0; bus < 2; bus++) {
     for (uint32_t address = LM75AD_ADDRESS; address < LM75AD_ADDRESS + LM75AD_COUNT; address++) {
-      if (!I2cSetDevice(address, bus)) { continue; } // Do not make the next step without a confirmed device on the bus
+      if (!I2cSetDevice(address, bus)) { continue; }  // Do not make the next step without a confirmed device on the bus
       uint16_t buffer;
       if (I2cValidRead16(&buffer, address, LM75_THYST_REGISTER, bus)) {
         if (buffer == 0x4B00) {
@@ -72,14 +74,14 @@ float LM75ADGetTemp(uint32_t sensor) {
   uint16_t t;
   if (I2cValidRead16(&t, Lm75.address[sensor], LM75_TEMP_REGISTER, Lm75.bus[sensor])) {
     int16_t sign = 1;
-    if (t & 0x8000) { // We are getting a negative temperature value
+    if (t & 0x8000) {  // We are getting a negative temperature value
       t = (~t) +0x20;
       sign = -1;
     }
-    t = t >> 5; // Shift value into place (5 LSB not used)
+    t = t >> 5;        // Shift value into place (5 LSB not used, expect 11-bit resolution)
     return ConvertTemp(sign * t * 0.125f);
   }
-  return NAN;  // Will be changed to "null" by ext_vsprintf_P()
+  return NAN;          // Will be changed to "null" by ext_vsprintf_P()
 }
 
 void LM75ADShow(bool json) {
@@ -87,6 +89,9 @@ void LM75ADShow(bool json) {
   for (uint32_t sensor = 0; sensor < Lm75.count; sensor++) {
     // Takes 2ms / LM75
     float t = LM75ADGetTemp(sensor);
+#ifdef LM75AD_SKIP_NULL_SENSOR
+    if (isnan(t)) { continue; }    // Skip sensor instead of reporting null value 
+#endif  // LM75AD_SKIP_NULL_SENSOR
 
     char name[16];
     strlcpy(name, "LM75AD", sizeof(name));                                                             // LM75AD
@@ -118,8 +123,7 @@ void LM75ADShow(bool json) {
  * Interface
 \*********************************************************************************************/
 
-bool Xsns26(uint32_t function)
-{
+bool Xsns26(uint32_t function) {
   if (!I2cEnabled(XI2C_20)) { return false; }
 
   bool result = false;
@@ -132,11 +136,11 @@ bool Xsns26(uint32_t function)
       case FUNC_JSON_APPEND:
         LM75ADShow(1);
         break;
-  #ifdef USE_WEBSERVER
+#ifdef USE_WEBSERVER
       case FUNC_WEB_SENSOR:
         LM75ADShow(0);
         break;
-  #endif  // USE_WEBSERVER
+#endif  // USE_WEBSERVER
     }
   }
   return result;