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Using an RJ45 Adapter to Connect to a DB9 Connector

In some situations it is necessary to interface the RS232 or RS485 signals to RJ45, terminal strips or other physical connections. The Digi radio modem has the RS232 and RS485/422 signals available on a DB9 connector. To facilitate adapting the DB9 connector interface to work with other physical connection types Digi offers RJ45 to DB9 adapters.

These adapters are shipped unassembled so that they may be put together to accommodate the needs of the application. Two adapters are available:

DB9 Male to RJ45 connector, Yellow adapter (p/n:JE1D2-CDA-A)
DB9 Female to RJ45 connector, Green adapter (p/n:JE1D3-CDA-A)
 
Wire color (Adapter) RJ45 pin # Wire color (Ethernet cable - EIA/TIA 568B )
Blue 1 White/Orange
Orange 2 Orange
Black 3 White/Green
Red 4 Blue
Green 5 White/Blue
Yellow 6 Green
Brown 7 White/Brown
White 8 Brown


An example application for these adapters would be to extend the RS232 serial connection so that the radio modem might be located closer to the antenna location so that the antenna cable will be as short as possible.

To build a 3-wire RS232 serial cable ( 3-wire refers to the three signals: RXD, TXD and GND), use a standard CAT-5 networking cable to act as the extension between the computer and the radio modem. (This cable will be carrying RS232 signals, not ethernet signals.)

  1. Assemble both the yellow and green adapter according to this table:

    DB9 pin RS-232 Signal Name Wire color (Adapter) RJ45 pin # Wire color (Ethernet cable)
    2 RXD Yellow 6 Green
    3 TXD Green 5 Blue/White
    5 GND Red 4 Blue

  2. When the adapters are assembled, test the cable by attaching the loopback plug into the yellow adapter and the CAT-5 cable, and the green one into the PC and the CAT-5 cable.
  3. Use the loopback test in the XCTU software to determine that packets can be transmitted correctly.
  4. Remove the loopback adapter and attach the radio modem.


To build an 8-wire RS232/RS485 serial cable for use with the Nema-4 enclosure, use a standard CAT-5 networking cable to act as the extension between the computer and the radio modem. (This cable will be carrying RS232 signals, not ethernet signals.)

  1. Assemble both the yellow and green adapter according to this table:

    DB9 pin RS-232 Signal Name RS-485 Signal Name Wire color (Adapter) RJ45 pin # Wire color (Ethernet cable)
    1 DCD   Orange 2 Orange
    2 RXD TX- Red 4 Blue
    3 TXD RX- Yellow 6 Green
    4 DTR   Blue 1 White/Orange
    5 GND GND White 8 Brown
    6 DSR   - - -
    7 RTS RX+ Black 3 White/Green
    8 CTS TX+ Green 5 White/Blue
    9 PWR(RI) PWR* Brown 7 White/Brown

  2. When the adapters are assembled, test the cable by attaching the loopback plug into the yellow adapter and the CAT-5 cable, and the green one into the PC and the CAT-5 cable.
  3. Use the loopback test in the X-CTU software to determine that packets can be transmitted correctly.
  4. Remove the loopback adapter and attach the radio modem.
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