Checked wires, measured voltages, -0.5 and +2.0 on TX and RX.
Bob
----- Original Message -----
From: "Steve Rooke" <[email protected]>
To: "Discussion of precise time and frequency measurement" <[email protected]>
Sent: Monday, May 24, 2010 10:10 AM
Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
Bob,
On 25 May 2010 00:27, Robert Benward <[email protected]> wrote:
Bob,
I just went out an ordered a bunch of gender changers and null modem cables,
and a DB9 tester (with a NM switch!). I started doing the same as you,
using a sharpie to mark my cable.
An update, the unit has been running overnight, the holdover light is on,
but nothing else. I still suspect the RS-232 is dead. I now have to
suspect my other antenna as well. It was good when pulled out of service,
but who knows. I wish I had my old Garmin 45 with the external antenna. I
also ordered an RS-422 adapter. I'm hoping I can connect with that.
Have you looked at the pins on the connector with a voltmeter at all?
If you have some voltage on pins 2 or 3 it will tell you which is the
transmitter for that end and give a good indication as to the life of
the interface. Just make pin 7 on the 25 way connector connect to pin
5 on the PC connector and then attach pins 2 and 3 to each end such
that the pin with voltage on at one end is attached to the pin with no
volts on at the other end. Sure if you cannot find any volts on any of
pins 2, 3, 4, 5 or 8, then you have a problem. You are using the lower
25 way connector on the Z3805A I hope. You need to talk to it a 9600,
8 bits, 1 stop bit and no parity.
Steve
Bob
----- Original Message ----- From: "Bob Camp" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Monday, May 24, 2010 7:15 AM
Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
Hi
Gotta label them *something* or sorting through them in the cable bin
becomes pretty difficult.
In addition to the wiring options you can (obviously) have either a male
or female on either end. There are so many "odd" pieces of gear out there
that you can have pretty much any combination.
Bob
On May 23, 2010, at 11:22 PM, Robert Benward wrote:
My experience with the term "straight through" is that I've seen RS-232
cable that have the ground pin connected to the shell. In a "straight
through" the pins are one to one and the only thing connected to the shell
would be the shield if one is available.
Bob
----- Original Message ----- From: "Bob Camp" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Sunday, May 23, 2010 9:21 PM
Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
Hi
Long ago I decided to go with the terms "straight" and "null modem" for
the cables I use. NM and ST are easy to mark and hard to confuse.
Bob
On May 23, 2010, at 8:58 PM, jimlux wrote:
Stanley Reynolds wrote:
<snip>
Dec computers / terminal servers were as I described, but many brands
were different. Still have a BOB aka break out box with LEDs to
indicate levels, matching transmit and receive is easy, getting the
hardware flow control / signaling right was a little more difficult.
straight cable = pin to pin
crossed cable = null modem = swapped pins
The phrase "null modem" comes from no modems or the configuration
that allows two singular ports to be connected, this cable would
cross the receive and transmit pins, and some would call it a cross
over cable. A null modem cable would be used to connect two computers
together and a program like kermit used to transfer files.
Yep.. DTE cable to DCE communications medium(phoneline) DCE to DTE
DCE == Modem (e.g. a Bell 202 or 212, for instance)
There were the flow control (RTS/CTS) used to turn around a half duplex
link. And, there are also the secondary transmit and receive (for a low
rate reverse channel). If you were receiving data from the link (DCE),
you'd assert RTS, and when the modem had switched, it would tell you CTS,
and off you'd go. (fancy modems used the reverse channel to send the
request to the far end, which would acknowledge... others just use a fixed
time delay) There are also pins for the clock (since some of these modems
were used on synchronous data links).
the "crossover" occured in the DCE to DCE link (that is, you'd transmit
from one DCE to the other DCE's receiver)...
the nominal cable between DTE and DCE was straight through. With no
real convention on male/female.. most devices had female sockets, and the
cables usually were male male plugs. IBM PCs had male on the chassis for
DTE, as did some PDT-110 (VT-100/LSI-11 smart terminals), but most other
terminals (the LSI ADM-x, Hazeltines, etc.) all seemed to have female, as
did the TI 800 series printer/terminals.
So, a "null modem" was a cable that emulated the DCE to DCE
connection..
there are/were various strategies on how sophisticated the reverse is..
do you also send the secondary channel? What about clocks? Most folks
ignored all that and used RTS/CTS
Or you strap RTS to CTS on your side, the other side does the same.
I think the phrase "standard cable" which could be null or straight
depending on the use is the confusing part.
Phone cables RJ11 and RJ45 swap the wires which is standard. Network
cables match the wires with the same color always on the right which
is standard. But even when a phone cable is standard it is not
interchangeable with a standard network cable. Again we have a need
for cross as well as straight network cables.
And, to make things worse, there are different "pair" arrangements.
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--
Steve Rooke - ZL3TUV & G8KVD
A man with one clock knows what time it is;
A man with two clocks is never quite sure.
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