On 9/27/23 16:01, Jesse Bertier wrote:
Fellow M100 Enthusiasts:
I kept at it, trying all the various suggestions from the group. I
finally solved the issue - the TNC had a loopback connection from DTR to
DSR. The problem disappeared entirely when I removed that loopback
connection the TNC was doing.
It's still curious, because looping back those two lines is perfectly
"legal".
It may possibly have a bad effect in some cases simply because of any
signal being a lie, but electrically it's perfectly legit. And it's not
even a data problem if neither side is looking at the signal.
I say, this indicates a problem in the 100 (in the design of the
circuit, not a damage you can repair) not a problem in the radio.
Though the work-around is still fine. I just mean that the conclusion
that "aha, the radio is the culprit" isn't really the case in my
opinion. But even if I think the root blame belongs to the 100, I'm not
sure there is anything you can do practically to fix the 100, and it was
simple to make use of an optional configuration in the radio that was
put there basically just for this reason, to cater to the failings, or
more generously, quirks of other equipment that might need it.
--
bkw
If interested, I posted the details here:
https://n1ugk.com/2023/09/trs-80-model-100-with-the-kpc-3/
<https://n1ugk.com/2023/09/trs-80-model-100-with-the-kpc-3/>
With that mystery solved, I can now use the M100 for what I intended to
use it for.
On Sep 8, 2023, at 7:28 PM, Daryl Tester
<dt-m...@handcraftedcomputers.com.au> wrote:
On 9/9/23 00:10, Jesse Bertier wrote:
I wanted to follow up with this issue - As it turns out, the TNC itself
seems to be the culprit, at least with the M100. Even small text strings
get garbled, with software flow control enabled on both sides. That TNC
works fine with a PC, just not the M100. Next time I have the scope out,
I’ll take a look at the line and compare, and work back into the M100 as
needed out of curiosity.
Sounds suspiciously like clocking tolerances (of the serial line). I
thought
it used to be 20% (from the "olden days") with 16x oversampling), but
current
Internet Wisdom (for what that's worth) says ~ 5%. If you've got one
device
that's slightly fast, and the other slower, you''ll see this sort of
behaviour.
(I used to work on a serial port switch in the 80's. That sod had
something like
a +0.5% tolerance, although its negative was relatively normal. The
above fault
was well known).
Cheers,
--dt
--
bkw