irrigation_system/software/test_modbus/boards/nucleo_f103rb.overlay

&usart1 {
	status = "okay";
	current-speed = <9600>;
	modbus0 {
		compatible = "zephyr,modbus-serial";
		status = "okay";
		// de-gpios = <&arduino_header 15 GPIO_ACTIVE_LOW>;	/* D9 */
	};
};