A low-cost general-purpose SCI (Serial Communications Interface) to RS232 adapter that is powered by the PC's RS232 port. It provides TX, GND, and RX connections for the SCI port of whatever MCU you're using.
When ordering, you must specify whether you need 3V or 5V (TTL logic level) compatibility to match your SCI.
RS232 'self-powered' adapter for TX, RX, and GND (3V or 5V versions)
Design and Development of Electronics and Software Systems