How can i use MAX485 to communicate with RS485 devices?

I have TXB0104 for voltage level translation and MAX485, but i don't
know how to generate the enable signal for MAX485.

It seems that the expansion header has only four pins for UART.

i googled a lot but didn't find any documents or a device driver for

Should i wirte my own RS485 device driver? Someone said that i could
use 'inverted TxD' as the enable signal for MAX485, but i'm not so
quite sure.

please help me.

You will definitely need a driver. You need something to tell it to switch. You could use the CTS signal for this purpose driven from the SW or you can make that pin a GPIO pin and drive it from SW as well. Just set it to the appropriate level to enable either transmit or receive via the MAX485.