The standard way to connect a serial port (RS232) to an Arduino (or any 0V/5V based serial interface) is to use a dedicated IC like MAX232A. With this IC, you don't need a 9V battery like with my ...

Arduino has shrunk the UNO R4 with the Arduino Nano R4 board equipped with the same 48 MHz Renesas RA4M1 32-bit Arm ...