From 7c9067b7b15a72ec5a8d59a571ec098a355b43c4 Mon Sep 17 00:00:00 2001
From: Theo Arends <11044339+arendst@users.noreply.github.com>
Date: Wed, 10 Feb 2021 15:56:06 +0100
Subject: [PATCH] Fix NTC calculation for ESP32

Fix NTC calculation for ESP32 (#10906)
---
 tasmota/xsns_02_analog.ino | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tasmota/xsns_02_analog.ino b/tasmota/xsns_02_analog.ino
index 73193a8af..6d581c4fd 100644
--- a/tasmota/xsns_02_analog.ino
+++ b/tasmota/xsns_02_analog.ino
@@ -42,7 +42,7 @@
 #define TO_KELVIN(x) ((x) + 273.15)
 
 // Parameters for equation
-#define ANALOG_V33                    3.3              // ESP8266 Analog voltage
+#define ANALOG_V33                    3.3              // ESP8266 / ESP32 Analog voltage
 #define ANALOG_T0                     TO_KELVIN(25.0)  // 25 degrees Celcius in Kelvin (= 298.15)
 
 // Shelly 2.5 NTC Thermistor
@@ -410,9 +410,9 @@ void AdcEverySecond(void) {
     if (ADC_TEMP == Adc[idx].type) {
       int adc = AdcRead(Adc[idx].pin, 2);
       // Steinhart-Hart equation for thermistor as temperature sensor
-      double Rt = (adc * Adc[idx].param1) / (1024.0 * ANALOG_V33 - (double)adc);
-      double BC = (double)Adc[idx].param3 / 10000;
-      double T = BC / (BC / ANALOG_T0 + TaylorLog(Rt / (double)Adc[idx].param2));
+      double Rt = (adc * Adc[idx].param1) / (ANALOG_RANGE * ANALOG_V33 - (double)adc);  // Shelly param1 = 32000 (ANALOG_NTC_BRIDGE_RESISTANCE)
+      double BC = (double)Adc[idx].param3 / 10000;                                      // Shelly param3 = 3350 (ANALOG_NTC_B_COEFFICIENT)
+      double T = BC / (BC / ANALOG_T0 + TaylorLog(Rt / (double)Adc[idx].param2));       // Shelly param2 = 10000 (ANALOG_NTC_RESISTANCE)
       Adc[idx].temperature = ConvertTemp(TO_CELSIUS(T));
     }
     else if (ADC_CT_POWER == Adc[idx].type) {