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Does RS422/RS485 work on Advantech PCM-5820?

Discussion in 'Embedded' started by Lewin A.R.W. Edwards, Jun 7, 2004.

  1. I just received an unpleasant surprise when trying to use differential
    serial on the Advantech PCM-5820. The system has jumpers for the
    second serial port; RS232, RS422 or RS485. In either RS422 or RS485
    mode, I see no activity at all on the TxD+/- pins.

    My software is asserting DTR and RTS, so I don't know what else I
    could possibly do to enable the drivers (and they should always be
    enabled in RS422 mode anyway, right?) I know I'm talking to the right
    I/O port and IRQ because when I jumper it back to RS232 I see activity
    on the TxD pin. I'm giving the board both +5 and +12, so it can't be
    missing an input voltage. I have ritually waved a White Castle
    hamburger over the machine and threatened it with a steak knife, with
    no discernible effect.

    I have jury-rigged the system to work on the port in RS232 mode by
    connecting Rx- on my DCE to gnd and Rx+ to TxD on the DTE, but
    although this proves my device is working, it is not deployable.

    Any ideas? Does this feature even work? Advantech's stellar
    documentation doesn't tell you how to use it at all, they just give
    you the pinout of the 14-pin connector on the board. You have to pull
    off the backshell to work out which pins go where on the "RS422/485"
    Lewin A.R.W. Edwards, Jun 7, 2004
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  2. Lewin A.R.W. Edwards

    Richard Guest

    I have a 5823, but I thought the com2 had a standard serial output connector
    for 232 and a seperate header for RS485.
    I'd have to check though.
    Richard, Jun 13, 2004
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  3. The 5820 has a 14-pin 2mm (7x2) header for COM2, and the board comes
    with a cable that has two DE9Ms on it; one for RS232, and one for
    Lewin A.R.W. Edwards, Jun 13, 2004
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