That's correct for a straight connection, i.e. not through the null-modem.
Maybe you can tell us the actual exact connection sequence between the 9 pin
male on the USB cable to the 25-pin female on the M100, especially at which end
the null modem is?
m
----- Original Message -----
From: Thomas Morehouse
To: m...@bitchin100.com
Sent: Tuesday, April 09, 2019 8:58 PM
Subject: Re: [M100] 102 com port power drain?
Thanks Kurt.
Testing the DB9-DB25 adapter only - not the usb/serial cable - I have
continuity NOT from pin 4 of the DB9 to pin 6 of the DB25. I have continuity
from pin 4 of the DB9 to pin 20 of the DB25. That's using the numbers printed
at the pins themselves.
Should I even bother testing the others you suggest? Sounds like the adapter
already fails the test.
Tom M.
On Tue, Apr 9, 2019 at 8:48 PM Kurt McCullum <ku...@fastmail.com> wrote:
Ignore the USB to serial piece of the puzzle. As Brian said, it's just a
serial port. Test the 9 to 25 adapter. One end will be female so it's easier to
put something like the end of a paper clip into one hole at a time then put the
probe on that.
Kurt
On Tue, Apr 9, 2019, at 5:22 PM, Thomas Morehouse wrote:
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 <bw.al...@gmail.com> 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 <ku...@fastmail.com
> <mailto:ku...@fastmail.com>> 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 <ku...@fastmail.com
>> <mailto:ku...@fastmail.com>> 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.
>>>
>>
>
