Simple USB to serial converter
This USB to serial (TTL) converter project is easy to build, it is simple and inexpensive. It is based on the PL2303SA USB to USART bridge from Prolific. The PL2303SA chip is not required an external crystal as the internal clock oscillator is continuously tuning up to USB bus frequency. Having chip in SO-8 packaging does not require special soldering skills to assemble the project. Please note: the TX and RX signal levels are 3.3 Volts.
PL-2303 SA is exclusively designed for mobile phones and embedded solutions, its small footprint easily installable to fit any connectors and handheld devices. With very small power consumption in either operating or suspend mode, PL2303SA is perfect for bus powered operation with plenty of power left for the attached devices.
PL2303SA provides a convenient simple solution for connecting an RS232-like full-duplex asynchronous serial device (TX-RX only) to any Universal Serial Bus (USB) capable host. PL2303SA highly compatible drivers could simulate the traditional COM port on most operating systems allowing the existing applications based on COM port (using TX-RX only) to easily migrate and be made USB ready. Flexible signal level requirement on the RS232-like serial port side also allows PL2303SA to connect directly to any 3.3V~1.8V range devices.