update NTC sensor.

Author: shaoziyang

sensor/NTC/README.md

@@ -1,18 +1,39 @@
 # NTC thermistor 
 
-NTC thermistor Sensor
+NTC thermistor Sensor.
 
 ![](ntc.jpg)
 
 
+There are two connection methods for NTC resistors: NTC connected to VCC or GND, as shown in the figure.
+
+![](ntc1.jpg)
+
+
+## description
+
+- NTC_GND(adc, max, B=3780)
+- NTC_VCC(adc, max, B=3780)
+
+  Convert numerical values to Celsius temperature.
+  
+  - adc, NTC input value, it can be voltage or ADC value.
+  - max, maximum value for ADC, it can be voltage (usually Vcc) or ADC value.
+  - B, B value of NTC resistor.
+
+If using esp32 series chips, use ADC.read_uv() to get ADC value for best optimal accuracy. 
+
 
 ## example
 
 ```python
 from machine import ADC, Pin
 
-ADC_TEMP = ADC(Pin(34))
-T = NTC(ADC_TEMP.read())
+ADC_T1 = ADC(Pin(34), atten=ADC.ATTN_11DB)
+ADC_T2 = ADC(Pin(33), atten=ADC.ATTN_11DB)
+
+T1 = NTC_VCC(ADC_T1.read_uv()/1000, 3300)
+T2 = NTC_GND(ADC_T2.read_uv()/1000, 3300, B=3950)
 ```
 
 From microbit/micropython Chinese community.  

sensor/NTC/ntc.py

@@ -2,13 +2,17 @@
     mpy drive for NTC thermistor Sensor
 
     Author: shaoziyang
-    Date:   2020.12
+    Date:   2024.4
 
     http://www.micropython.org.cn
 
 '''
 import math
 
-def NTC(adc, B=3780, bits=12):
-    t1 = math.log(adc/((1<<bits)-adc))/B + 1/298.15
-    return 1/t1 - 273.15
+def NTC_GND(adc, max, B=3780):
+    t1 = math.log(adc/(max-adc))/B + 1/298.15
+    return 1/t1 - 273.15
+
+def NTC_VCC(adc, max, B=3780):
+    t1 = math.log((max-adc)/adc)/B + 1/298.15
+    return 1/t1 - 273.15