USB-Serial Bridge: OK to leave GPIO 0 to 7 of CY7C65213 floating? (KA-03327)
GPIOs can be left floating if configured as output pins. If the ports are configured as input pins, these ports must be connected to pull-up/pull-down resistors. Recommend resistor power is 10 kW. More https://community.infineon.com/t5/Knowledge-Base-Articles/USB-Serial-Bridge-Controller-FAQs-KBA22405... here.