Creating a USB to RS485 converter with FT232RL chip
Document ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf, page 33 says that CBUS2 - TXDEN (RS485 direction select)

Default configuration of CBUS2 – Transmit data enable for RS485 is enabled.

Check the pins used to enable the TXDEN.