Wemos S2 Mini Serial Monitor issue (and fix)

I recently purchased some Lolin/Wemos S2 Mini boards (the ESP32 successor to the popular Wemos D1 Mini that uses the ESP8266).

Whereas there were hardly any changes required for programming and uploading to the D1 Minis, there were several additional steps for uploading sketches to the S2 Mini.

Namely you have to hold the 0 button down and then press the RST button to put the board into a firmware update mode, before you can upload you sketch. So far so good.

My issue though was that despite apparently matching all the settings in the Wemos documentation (Get started with Arduino [S2 series] — WEMOS documentation) and being able to upload sketches, nothing would appear on the Serial Monitor. Nothing, not even garbled text. Serial monitor would remain blank.

I've been playing around and have just discovered that setting the board to "ESP32S2 Native USB" appears to have fixed the issue. Serial monitor now works. Hopefully this will help others.

2 Likes

Thanks. That worked for me also. I was just getting to the cursing stage when I saw your post.
I ran Coremark against it and it scored 361.38. I measured it at 0.137W while running it also. Compared to an ESP-WROOM-32 at 351.23 Coremarks and 0.37W, this is a great little module. Cheap also. I just wish it was easier to get in the US. My order from AliExpress took several weeks to arrive.
I need to look at battery powering now. Thanks again! Bill

Glad it helped somebody!

I actually ended up with more issues trying to get stuff to work with those modules, so I've mothballed them and am back to using D1 Minis again, for now. Hopefully an IDE update or two will make the process a bit smoother.

I'm running the Arduino IDE on a Mac
In my case I had to use the ESP32S2 dev module and the setting kind of like the documentation (outdated..) is saying.

It would not print to my serial console either until I pressed the RST (reset) button on the S2 mini.

I got this message in the IDE:

Leaving...
ERROR: ESP32-S2FH32 chip was placed into download mode using GPIO0.
esptool.py can not exit the download mode over USB. To run the app, reset the chip manually.
To suppress this error, set --after option to 'no_reset'.
To suppress this error, set --after option to 'no_reset'.

My IDE settings: (note: Upload Mode:"Internal USB" or "UART0" doesn't make a difference.)

There are a lot of extra options in Arduino IDE for the ESP32 S2. Like shown in the above picture.
Where can I find a description of the meaning of them all. I can only guess some of them.

Another question: where does the Serial output go to? I made a sketch which spews out serial data, but I scoped all pins and found nothing.
When the board was brand new, a COM port appeard in Windows when connected. But after uploading the first Arduino sketch, that port is gone. Now there is only a COM port in bootloader mode.

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.