OK - looks like I wasn't clear. In Kurt's post, he writes:
"Take one probe of the meter and put it on pin 4 of the DB9 and
the other on pin 6 of the DB25. It should beep or light up
(however you meter functions to indicate a connection). Then do
the same for the DSR line on pin 6 to pin 20. And finally the
RTS and CTS pins 7->5 and 8-> 4. If they are crossed in some
manner, then you will not get a beep or a light."
If the usb/serial cable is a single unit (usb at one end, DB9 at
the other), how do I put one probe of the meter on the DB9 and
the other probe of the meter on the DB25? There's no DB25 on
the cable, unless I plug the 9-25 adapter into the DB9 - but
then I can't put a probe on the DB9. Jeez I feel dense.
I'm really sorry I can't follow this, but maybe I'm just
overlooking something really simple?
Thanks.
Tom M.
On Tue, Apr 9, 2019 at 7:56 PM Brian K. White
<[email protected] <mailto:[email protected]>> wrote:
You don't check continuity on the usb-serial adapter. That
isn't just a
cable, it's really a peripheral like a disk drive or a
printer, it just
happens to be a peripheral that all fits entirely inside the
plug
housing on one end of it. There is no simple direct wire
mapping between
the usb pins and the serial pins. Between the usb pins and
the serial
pins, there is circuit board with a chip and a few other
components
which is converting and translatine between two entirely
different kinds
of signals and protocols.
You treat the usb-serial adapter as just a serial *port*,
and ignore
that it looks like a wire. Just pretend it's like a serial
port built in
to the back of an old desktop.
You check the continuity of the serial cable, which IS "just
a cable".
Or, really, you check the continuity of the combined serial
cable with
any null-modem and gender-changer adapters, and treat that
all together
as one "cable".
--
bkw
On 4/9/19 6:56 PM, Thomas Morehouse wrote:
> Thanks Kurt. I'm even denser than usual tonight I guess.
>
> From earlier posts, seems the problem (102 screen
dimming) is likely
> caused by the usb/serial cable. One end of the cable is a
usb plug;
> other end is the DB9.
>
> So I'm afraid I don't know how to test continuity on the
cable. I can
> find pin 4 of the DB9 - but where does the DB25 fit in the
picture?
>
> Or, are you saying to test the cable with the DB9/DB25
adapter plugged
> into the cable?
>
> Sorry to be the dolt again.
> Tom M.
>
>
> On Tue, Apr 9, 2019 at 10:57 AM Kurt McCullum
<[email protected] <mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>>
wrote:
>
> There are store bought cables that work well. Brian
has done a
> great job putting together a list of those cables. For
my machines
> I have a mixture of custom made cables or slim
adapters. Both
> methods work and give me the pinout below. When you
get the cable
> right, your M102 will be happy.
>
> But to the question at hand, don't tear apart your
cable. Check
> it. Right now you know that pins 2,3 and 5 are all
going to the
> right locations. You will need to check pins 4,6,7 and
8. Since
> those are paired lines (4/6, 7/8) one or both pairs
will be flipped.
>
> If you have a multi-meter which has a continuity check
on it then
> you test both ends of the wire.
>
> Here is what I have found to work on all my machines
and I include
> this in the mComm manual.
>
> 7 Wire Cable
> PC
>
> Model-T
> DCD
> 1
> NC
>
>
> RX
> 2
> →
> 2
> TX
> TX
> 3
> ←
> 3
> RX
> DTR
> 4
> ←
> 6
> DSR
> GND
> 5
> ↔
> 7
> GND
> DSR
> 6
> ←
> 20
> DTR
> RTS
> 7
> →
> 5
> CTS
> CTS
> 8
> ←
> 4
> RTS
> RI
> 9
> NC
>
>
>
>
> Take one probe of the meter and put it on pin 4 of the
DB9 and the
> other on pin 6 of the DB25. It should beep or light up
(however
> you meter functions to indicate a connection). Then do
the same
> for the DSR line on pin 6 to pin 20. And finally the
RTS and CTS
> pins 7->5 and 8-> 4. If they are crossed in some
manner, then you
> will not get a beep or a light.
>
> Hope that makes sense.
>
> Kurt
>
>
> On Tue, Apr 9, 2019, at 7:38 AM, Thomas Morehouse wrote:
>> Thanks for the comments gents. Learn something every day.
>>
>> Kurt, on the "crossed wires" issue, what is the
procedure for
>> fixing the problem? I sure don't want to pull
something apart,
>> or buy even *more* adapters!
>>
>> Thanks.
>> Tom M.
>>
>>
>> On Tue, Apr 9, 2019 at 10:03 AM Kurt McCullum
<[email protected] <mailto:[email protected]>
>> <mailto:[email protected]
<mailto:[email protected]>>> wrote:
>>
>>
>> What you are describing happens to me when the
either the
>> CTS/RTS or DTR/DSR wires in your cable are crossed.
>>
>> Example. The CTS pin listens (checks for voltage)
to the RTS
>> pin on the other end. If you have a cable where
RTS goes
>> straight to RTS and CTS going straight to CTS,
then you have
>> two ends of the cable both feeding voltage to the
same wire.
>> This causes the screen to go dim. the DTR/DSR
pins can
>> produce the same issue.
>>
>> Kurt
>>
>> On Tue, Apr 9, 2019, at 5:33 AM, Thomas Morehouse
wrote:
>>> Now that I've got my usb/serial link working
(M102 to Dell
>>> laptop), I notice the 102's screen get quite dim
when the
>>> cable is in the 102's 25 pin serial port.
>>>
>>> Doesn't need to be connected to the Dell. Just
when you plug
>>> the usb/serial cable into the 102. Unplug the
cable, 102
>>> screen returns to normal visibility.
>>>
>>> Something to worry about? or just live with it?
I wouldn't
>>> have thought the usb/serial cable chip would put
such a
>>> drain on the system. Happens with battery power,
or even
>>> with external 6 volt poweer.
>>>
>>> Thanks.
>>> Tom M.
>>>
>>
>
