goes to flash mode when it is powered externally

Hasan Shadi
Posts: 26
Joined: Tue Mar 31, 2020 7:26 pm

goes to flash mode when it is powered externally

Postby Hasan Shadi » Mon Apr 20, 2020 9:41 am

I am working on windows 8.1 with ESP-IDF 4.0 release, using the ESP-IDF cmd that was installed automatically with the ESP-IDF setup '.exe' file. When I power the ESP32-NodeMCU externally, it starts the flash mode automatically, but rather than that, it should run its app by default. I have attached a picture of the ESP32 development board that I have. When I power it up externally along with the USB cable connected to it, it also goes to the flash mode automatically, even if I restart it multiple times, keeps getting the flash mode. As a proof, when I press the 'boot' button, it stops flashing, which is logical. When I disconnect the external power and restart it, it runs the app normally. The same thing applies when I feed the 3.3 V to the 3v3 pin. However, this is a real problem for me, I have no idea why is this happening. Moreover, I think that there is another problem that might be related to the same problem that I am facing now, when I power it up using the USB cable, it provides 2V from the 5V pin, but the GPIO pins provide 3.6V which correct. Even the 3.3v provides a very small voltage. I have sensed all the 3 voltage regulators, all of them are providing the correct voltage when I power them externally (not from the USB cable), which is 3.3 V as the correct voltage. But, when I power them up from the USB cable, all of them provide (as an output) a very low voltage, like 0.42 V. What is killing my mind is that it runs normally when I provide it with electricity from the USB cable and gives like 0.42 V out from the voltage regulators, knowing that the USB cable provides 5 V. I have provided all the information that I have until now. This is the product link on ali-express: https://www.aliexpress.com/item/32656775273.html
Attachments
ESP32_NodeMCU.PNG
ESP32-NodeMCU development board picture
ESP32_NodeMCU.PNG (297.58 KiB) Viewed 3402 times

Hasan Shadi
Posts: 26
Joined: Tue Mar 31, 2020 7:26 pm

Re: goes to flash mode when it is powered externally

Postby Hasan Shadi » Mon Apr 20, 2020 7:36 pm

I had a misunderstanding about the board that I have, there is nothing with the board, it is correctly manufactured from the company that I bought the chip from. My misunderstanding is that I am feeding it 5V from the 5V pin, the 5V is only meant to be used as an output voltage, not an input voltage, which is causing it to go to flash mode and weird stuff going on. But, the 3v3 pin can be used to output AND input 3.3V. However, this applies to my development board, it may differ from the other development boards. Even the GND that is next to the 5V pin has like 5 or 6 ohms as a resistance (I have measured it relatively with the USB cable, of course it is acting as a GND for the ESP32), how could a GND have some resistance? this is impossible!?
So I have just decided to leave the 5V pin and the GND pin that is near to it.

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