After installing Arduino IDE 1.8.12 the Serial Monitor does not set the baudrate I selected. I have to choose the twice as low baudrate as it actually is, i.e. 57600 instead of 115200, 115200 instead of 230400 and so on.
Which board do you have selected from the Arduino IDE's Tools > Board menu?
The problem happens to be only with Arduino Pro Mini 3.3V. Tried with ESP32 Dev Kit, it works properly.
I have double checked selecting Pro Mini 3.3V, the problem persists.
The problem is the Pro Mini 3.3V board selection is configured for an 8 MHz clock, but the board you are using has a 16 MHz clock. You can't make your Pro Mini run at 8 MHz just by selecting the Tools > Processor > ATmega328P (3.3V, 8 MHz) option. It's going to run at the clock speed of the resonator that's soldered on the board regardless of which setting you choose from the menu. The only difference is the F_CPU macro is set to 8000000L instead of 16000000L, which throws all timing related functions off, including serial communication.
If you really want to run your board at 8 MHz, you do have the option of using the internal oscillator. You'd need to:
- Install a board definition that is configured to use the internal oscillator. MiniCore will provide that: GitHub - MCUdude/MiniCore: Arduino hardware package for ATmega8, ATmega48, ATmega88, ATmega168, ATmega328 and ATmega328PB
- Connect an ISP programmer to your board.
- Do a Tools > Burn Bootloader to configure the fuses on your board to use the internal oscillator.
I am pretty sure that it is 8 Mhz 3.3V. It has a tiny 8Mhz crystal. I have even tried programming it to 16Mhz. Nothing has changed. I will restart my PC after saving my project and will try again.
Restarted my PC, nothing has changed. Printing a text at 230400 baud, but Serial Monitor needs to be set to 250000.
Could not burn the boot-loader. Maybe the serial adapter is damaged.