TX管脚可以悬空不接。RX管脚可以下拉到地。请参考下面的帖子说明。
The Tx pins that are not used can be left open. The Rx pins that are not used should be connected to GND through a 50 ohm resistor, we are not expecting RF transmission so a standard resistor is OK. The Rx inputs are AC coupled. e2e.ti.com/.../737123
