iduino FTDI Basic Program Downloader USB to TTL 3.3V-5V FT232 Module Board for Arduino Compatible Chipset FT232RL almost like the original one with stable performance. With a build-in signal voltage switch  select 5V or 3.3V(3V3) for the power at TXD and RXD as you switch. With RXD and TXD transceiver communication indicators. Turn ordinary USB serial port, using TTL module, download on STC microcontroller Packing list: 1 * USB to Serial Adapter Module