* If the main script doesn't exist, or exits, REPL (read-evaluate-print-loop) mode is entered. This gives you a standard Python interpreter prompt over the USB serial device. Exiting from this will soft-reset the board. | * If the main script doesn't exist, or exits, REPL (read-evaluate-print-loop) mode is entered. This gives you a standard Python interpreter prompt over the USB serial device. Exiting from this will soft-reset the board. |