Just for fun, I found this: http://www.ossmann.com/5-in-1.html
Ah, quite a fun article.
That made me think that the pinout differences we see could be explained by whether the hardware is intended to act as the DCE or DTE, and what it expects to be connected to the port. It reminded me of old "null modem" setups for when you connect the "wrong" things directly together, and some assumptions had to be made.
You have got right to the relevant point.
And those "helpful" tables which just label a signal at one pin are generally
very unhelpful, often to the point of confusion.
I come from a time when DB-25 connectors were the standard and an RS-232 interface lead was only used to connect an item of DTE to an item of DCE. Progress occurred and I was regularly making up "special" interface leads for those who wished to connect an item of DTE to another (possibly different) item of DTE. Without much effort I can quote "2, 3, 4, 5, 6, 7, 8, 20 & 22" along the defined signal on each pin.
Here follows my
helpful table for a serial console lead to use with the gubbins --
Signal 8P8C DE-9 Signal |
- 1 6 DSR |
- 2 1 DCD |
- 3 4 DTR |
GND 4 5 GND |
TxD 5 2 RxD |
RxD 6 3 TxD |
- 7 8 CTS |
- 8 7 RTS |
The first column, headed "
Signal", relates to the second column, headed "
8P8C". A hyphen in the first column signifies that there is no connection made to the pin of the socket (within the gubbins). The fourth column, also headed "
Signal", relates to the third column, headed "
DE-9". For each of the eight rows, the pin number stated in column two is connected to the pin number stated in column three.
Having performed an experiment, I now know the above is correct.
The form of the experiment came to me whilst I was laying in my bed, considering the insides of my eyelids, early this morning. For the experiment I used the following items --
- A standard Ethernet patch lead (not a cross-over Ethernet lead).
- A 8P8C socket which was labelled "BT ISDN 2" and complete with the "prancing piper" logo.
- Three lengths of 0.5mm solid core, PVC insulated, wire.
- A DE-9, female, plug with screw terminals for the wires.
Having connected the 8P8C socket to the DE-9 plug as in the table, above, a connection was made from the gubbins' serial console port to the computer's RS-232 port. A logging screen session was started --
screen -L -U /dev/ttyS0 9600Upon powering up the gubbins its boot time messages, followed by an invitation to login, were displayed --
NBpNBfz
Covaro Bootloader: 08/06/09.15:04
Helium 500/400 PP boot v1.6
Loading from active partition.
NP
i 100%
Booting... Please wait.
Boot time: Mon Feb 14 13:51:39
Network Interface Device (NID) 2.1.6-406 (Sep 2 2010)
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