ESP32 Forum

I am trying to run an ESP-IDF app on my ESP32 that sends sensor readings to a web server on my Ubuntu machine, I have attached it to 2 batteries and pins to Vin and Gnd with 3.40V. When I connect the ESP32 to a USB port on my PC, it transmits data just fine to my server. But when I connect it to the batteries it does not transmit any data. Both the ESP32 and the MPU6050's onboard LED power up though. What am I doing wrong here?

If it were me, I'd attach an external UART->USB connector to the RX and TX pins of the ESP32 and see what the console is saying during boot.

Which pins on the development board are you connecting the 3.4V out of the battery to?

To the VIN and GND pins.
@kolban thanks for the reply, unfortunately I don't have access to a USB->UART connector right now.

Vin is the LDO input (+5V pin from USB). If the battery voltage is 3.4V, it is probably not enough to give 3.3V on LDO's output (pin 3V3).
You could use the LiFePO4 battery connected directly to 3V3 pin to power the board.

Hi @loboris, if I connect my 3.4V connection to 3v3, where do I connect my I2C sensor's VCC then?

sheikhumar93 wrote:Hi @loboris, if I connect my 3.4V connection to 3v3, where do I connect my I2C sensor's VCC then?

It the sensors can be powered from 3.4V, connect them to 3.4V, if thay require some other voltage, you must use separate LDO to power them and some level shifter. Most of the I2C sensors should work with 3.4V.
Be carefull if using Li-Po batteries, fully charged they can have voltage too high for ESP32.