Rs-485 Wiring Diagram; Rs-485 (4-Wire) Operation And Rs-422 Operation - Digi XBee User Manual

RS-485 wiring diagram

The following figure shows the RF Modem in an RS-485 (2 wire) half duplex:

RS-485 (4-wire) operation and RS-422 operation

XCTU that with the RS-485 variant of the 900HP RF Modem, the RF Modem is defaulted with the D7 command (AT
parameter) to 7. This parameter controls the TX enable signal and allows the modem to output any data in the DO
buffer to the host device for the RS-485/422 interface. In the event that the parameter is accidentally changed, which
would halt RS-485 communication, a USB mini cable should be plugged into the modem to reconfigure it. You can
reconfigure by using Digi's XCTU.
With the USB plugged in:
1. Open XCTU and select the Com port of the USB.
2. Select the Terminal tab and type "+++". The system will respond with "OK".
3. Type "ATD77" then <Enter>, and the system will respond with "OK".
4. Type "ATWR" then <Enter>, and the system will respond with "OK".
5. Type "ATCN" then <Enter> to exit command mode, and the system will respond with "OK".
6. Unplug the USB and return to the existing RS-485/422 interface. The 900HP RF Modem is now ready to
communicate in RS-485 mode.
Note Failure to enter AT Command Mode is most commonly due to baud rate mismatch. Ensure the 'Baud' setting
on the "PC Settings" tab matches the BD (Interface Data Rate) setting of the RF modem (by default, BD
parameter = 3, which is associated with 9600 baud).
XBee/XBee-PRO 900HP RF Modem User Guide
RS-485 (4-wire) operation and RS-422 operation
16