I'm having a problem with connecting to my ESP32S dev board using Thonny. When I connect to the board using the board's USB-to-serial port, I get a whole lot of rubbish output (as shown in the below image). How do I get it to stop so that I can flash/load MicroPython onto the board?

I've also tried using uPyCraft to flash the board, but the firmware download fails, as does updating the IDE.