Started by add30417, November 19, 2021, 12:44:19 PM

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Hello Together,

I have a issue with one of my ESP32-PoE-ISO. When I'm plugging on my MAC, no additional Serial Port is shown in the Arduino IDE (with a other ESP32-PoE-ISO is working fine). So I guess, it is HW issues with this one device.

I was trying to use a Arduino USB2Serial Adapter ( for flashing. So far, I can read the log on the Serial Console, but flashing isn't possible. (I already entered the FLASH Modus)

I guess some settings (e.g. Board) are wrong at Arduino IDE.

Have someone the same case in the past? Which Settings should I use for flashing?



Maybe the UART responsible for programming was disabled by either software or hardware means? Double-check that.

Where did you connect the external USB-serial adapter? The firmware defines which pin is meant for programming and which is general purpose UART. You can't connect it to the UART at the UEXT and expect to program the board from there.

By the way, a lot of people reported similar ESP32-MAC issues here, you might find some of the suggestions helpful:
Technical support and documentation manager at Olimex


I connected like:

TX on Pin3
RX on Pin1

As i mention, i can see the Serial logs from my flashed sketch with this Setup.

When the Board is starting, i keep pressing the Reset boot to enter the flash mode, right?


No need to press reset. The board auto-connects in bootloader mode.

You see logs yes, and that is a sign this is not the serial interface used to program the board. It is other serial meant for general usage.
Technical support and documentation manager at Olimex


Thanks for support.

But how can I flashing the board with a external device?


There are software ways and hardware ways.

For example, in ESP-IDF you can change which UART to be used for debugging from make menuconfig -> component config -> ESP32-specific -> UART and change from UART0 to UART1. Then you can access UART1 at the UEXT and UART0 will be free.

For the hardware approach - it doesn't make a lot of sense but probably you would need to disconnect the built-in CH340T USB-serial converter and connect your external USB-serial converter at the same data lines. These U0RX and U0TX pins can also be found at the EXT headers for easier access.
Technical support and documentation manager at Olimex