vcc = ESP.getVcc() inaccurate in 2.4.0-rc2 version?

[sam77277]

Basic Infos

Hardware

Hardware: ESP-12
Core Version: 2.4.0-rc2

Description

I connected A0 pin to 3V pin and connected power to 3V pin. The value of "vcc = ESP.getVcc()" in 2.4.0-rc2 version is inaccurate, but the value in 2.3.0 version was accurate that was the same voltage as power. It was wired.

Settings in IDE

Module: ?Generic ESP8266 Module?
Flash Size: ?4MB?
CPU Frequency: ?80Mhz?
Flash Mode: ?qio?
Flash Frequency: ?40Mhz?
Upload Using: ?SERIAL?
Reset Method: ?nodemcu?

Sketch

ADC_MODE(ADC_VCC);

void setup() {
   Serial.begin(115200);
}

void loop() {
int vcc = ESP.getVcc();
Serial.println(vcc);
delay(1000);
}

[igrr]

IIRC you have to keep A0 disconnected if you wish to use getVdd.

…

On Sun, Nov 5, 2017, 18:43 sam77277 ***@***.***> wrote: Basic Infos Hardware Hardware: ESP-12 Core Version: 2.4.0-rc2 Description I connected A0 pin to 3V pin and connected power to 3V pin. The value of "vcc = ESP.getVcc()" in 2.4.0-rc2 version is inaccurate, but the value in 2.3.0 version was accurate that was the same voltage as power. It was wired. Settings in IDE Module: ?Generic ESP8266 Module? Flash Size: ?4MB? CPU Frequency: ?80Mhz? Flash Mode: ?qio? Flash Frequency: ?40Mhz? Upload Using: ?SERIAL? Reset Method: ?nodemcu? Sketch ADC_MODE(ADC_VCC); void setup() { Serial.begin(115200); } void loop() { int vcc = ESP.getVcc();//readvdd33(); Serial.println(vcc); delay(1000); } — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#3800>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AEJcevbB2DGCsAp8dkOs93ulMe8cVVVsks5szZFTgaJpZM4QSVQL> .

[sam77277]

Despite whether I connected or disconnected A0, the Vdd was 10% difference between using 2.4.0-rc2 or 2.3.0 version. If I want to get the accurate reading, I have to use 2.3.0 and connect A0 to 3V.
I still confused. By the way I use Wemos D1 mini.

[comino]

According to the nonOS datasheet :
Power voltage of VDD33; unit: 1/1024 V

So to get the 'correct' voltage in V you need to divided be 1024. Like:
float vccVolt = ((float)ESP.getVcc())/1024;

Did you do that?

[tablatronix]

The wemos d1 mini has a resistor divider on A0, so your test is flawed.

[devyte]

Previous comment is correct. Closing due to user error.

[ishwariyjoshi]

can we use ESP.getVcc(); funtion in ESP32 to read VCC voltage ?