HeltecTM ESP32+Arduino Series Frequently Asked Questions


This page contains the most frequently questions from user. If this page’s detail can’t solve your problem, you can also talk in our forum: community.heltec.cn


Can’t Download Firmware

  • Use a better USB cable, or change a USB socket;

  • Check and make sure the CP210x drive had been correctly installed, users can refer to this document: Establish Serial Connection;

  • Press “PRG” button before upload.


Another Communication Bus Usage Example


System Reset All the Time

According to the situation we have collected so far, the most likely to cause a constant reset problem may have two reasons:

  • Power supply problem: please make sure the voltage of USB ≥ 4.7V, 300mA;

  • You chose an error board: because each type of board may have a different FLASH size, and they have a different partition map, it will cause the internal logic error.

Vext Control

The Vext is a power source for external devices. Refer from the schematic diagram, It’s controlled by GPIO21:

  • GPIO 21 --> LOW --> Vext(3.3V/250mA) ON

  • GPIO 21 --> HIGH --> Vext(3.3V/250mA) OFF


The Vext features is very important for some devices without deep sleep mode. When the system need in deep sleep status, we can turn off the Vext by set GPIO 21 to HIGH, then to save energy.