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Digi EtherLite
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Building:

* Fetch srpm.  Install with ``rpm -ivv`` ::

    cd /root/rpmbuild/SPECS
    rpmbuild -bb dgrp-1.9.spec
    rpm --install RPMS/x86_64/dgrp-1.9-30.x86_64.rpm

Cabling
-------

XREF ftp://ftp1.digi.com/support/cabling/90000253_E.pdf

For a standard RJ-45 to D-shell converter, the RJ-45 side enumerates
onto colors as ::

    Blue(1) Orange(2) Black(3) Red(4) Green(5) Yellow(6) Brown(7) White(8)

On Digi devices, these are labeled as ::

    RTS(1) DSR(2) DCD(3) RXD(4) TXD(5) GND(6) DTR(7) CTS(8)

To make a female DE-9 connector for mating with a standard PC,
its pinout is ::

    DCD(1) RXD TXD DTR GND
       DSR RTS CTS RI(9)

Notice that there is no analog for ring indicator in the EtherLite, so we
can't bring that across.  In any case, the mating pins are ::

    DCD TXD RXD DSR GND
      DTR CTS RTS RI

(The Digi manual has a bizarre thing going on with DCD and DTR; it suggests
shorting pins 1 and 6 of the DE-9 and leaving DSR (pin 2 of the RJ45)
unconnected.)

Our final wiring schematic, ignoring the Digi funniness above, is, staring
FORWARD INTO THE DEVICE, that is, with the colored wires facing you, ::

   Black(DCD) Green(TXD) Red(RXD) Orange(DSR) Yellow(GND)
     Brown(DTR) White(CTS) Blue(RTS) N/C

Alternatively, with the Digi funniness it's the less useful ::

   Brown(DTR) Green(TXD) Red(RXD) Black(DCD) Yellow(GND)
           Brown(DTR) White(CTS) Blue(RTS) N/C

For DB-25M connections (A-side; if that doesn't mean anything to you, ignore
it), the pinout to color guide is

    ============    ===================
    DB-25 Pin       RJ-45 Pin and Color
    ============    ===================
        2 (TXD)            5 (Green)
        3 (RXD)            4 (Red)
        4 (RTS)            1 (Blue)
        5 (CTS)            8 (White)
        6 (DSR)            2 (Orange)
        7 (GND)            6 (Yellow)
        8 (DCD)            3 (Black)
        20 (DTR)        7 (Brown)
    ============    ===================

Unfortunately, it looks like some of our serial converters ended up wired
thusly::

   Yellow Green Red Orange Black
     Brown White Blue   N/C

To compensate, rather than using straight-thru ethernet cables, crimp ones
which are straight-through, except swap pins 3 and 6.  This is even sort of
convenient since those pins are on one twisted pair in standard Ethernet
pinouts.  Or just fix the connectors so we don't end up with a pile of
miswired Ethernet cables.

Some random musings
-------------------

=========   ======  ===========
RJ45 DIGI   SERIAL  RJ45 SERIAL
=========   ======  ===========
1 WO        RTS        8 Br
2 O         DSR        2 O
3 WG        DCD        4 Bl
4 Bl        RXD        3 WG
5 WBl       TXD        6 G
6 G         GND        5 WBl
7 WBr       DTR        7 WBr
8 Br        CTS        1 WO
=========   ======  ===========

Equivalently, that means the "serial" end is: Br O Bl WG G WBl WBr WO

APC MasterSwitch
----------------

APC MasterSwitch uses a custom pinout.  When making an adapter for one of those
for use with a straight-thru ethernet cable, the pinout is, FORWARD INTO THE
DEVICE, that is, with the colored wires facing you, ::

   NC NC NC NC Red(RXD) Green(TXD)
     Black NC NC NC