The FT4232HQ Quad USB-UART provides a UART connection through the micro-AB USB connector. The FPGA UART TX/RX (two-wire) connection is made through the FT4232HQ BD port. Channel BD implements a 2-wire level-shifted TX/RX UART connection to the FPGA. The FTDI FT4232HQ data sheet is available on the FTDI website: https://www.ftdichip.com/.