The nonemcuv2 has only 1 ADC and it measures 0 to 1023 when the input voltage varies from 0 to 3.3vdc. However the 8266 core code says it is “restricted to 0 ~ 1.0V”. I just need to measure 20C to 30C from LM35.
In 'core_esp8266_phy.cpp'
vdd33_const the voltage of PA_VDD x=0xff: it can measure VDD33,
18<=x<=36: use input voltage, the value is voltage*10, 33 is
3.3V, 30 is 3.0V, x<18 or x>36: default voltage is 3.3V
the value of this byte depend from the TOUT pin usage (1 or 2):
1) analogRead function (system_adc_read()): is only available
when wire TOUT pin17 to external circuitry, Input Voltage Range
restricted to 0 ~ 1.0V. For this function the vdd33_const must
be set as real power voltage of VDD3P3 pin 3 and 4 The range of
operating voltage of ESP8266 is 1.8V~3.6V,the unit of
vdd33_const is 0.1V,so effective value range of vdd33_const is
[18,36] 2) getVcc function (system_get_vdd33): is only
available when TOUT pin17 is suspended (floating), this
function measure the power voltage of VDD3P3 pin 3 and 4 For
this function the vdd33_const must be set to 255 (0xFF).
/*[107] =*/ 33,