Don't the cisco cables have a rj45 on one end, and db9 on the other?
Don't you need a dupont connector for the tpdd, and a 9-25 adapter for
the M100?
And do they actually include dsr/dtr?
Myself I am hoping to no longer use the db25 pcb. I just made a new
version just for the heck of making a more optimized version of it. I
think the most optimal is with the pcb and transistors on the tpdd end,
because it takes care of the 2x4 plug for the tpdd in a much more
convenient way than crimping and assembling a dupont connector. And the
cable and db25 comes from any generic factory molded modem cable. The
latest version I added a place to zip-tie the cable end to the pcb, and
I think that will be the final most optimal version.
But my first samples haven't arrived yet so it's still a theory.
It might actually be worth making a little 3d-printed housing for the
tpdd-end, to fill up that opening in the case just like the original
cable does. Not just for polarity, but also to provide strain relief,
where the case opening is what holds the cable in place instead of the
pins soldered on the pcb inside the tpdd. But that's honestly not a
major worry and I haven't actually tried to design anything.
--
bkw
On 7/17/19 1:57 PM, Kurt McCullum wrote:
Brian,
I appreciate the insights. My first reaction to seeing your new board
was that this was a good solution. But after reading through your
post, I changed my mind. It's probably still much easier (and cheaper)
to buy the FTDI cable designed for CISCO routers, clip off the RJ45
end and then solder on the DB25. Those cables have the proper levels
and it's easy enough to solder the DB connector. The only thing I
don't like is the flat, light blue, cable.
Kurt
On Wed, Jul 17, 2019, at 10:49 AM, Brian K. White wrote:
Kinda sorta maybe possibly. I had thought about using one of the
variants of max232, instead of the 3 transistor hack. But in the end,
the 3 transistors is probably the cheapest and simplest circuit to make
a tpdd work, and this new circuit with the part that Rick Shear
identified, really does seem to be just like the original cable. I
haven't used a scope to compare the actual signals, but I have a scope
and an original cable so I could. I think I'll do that.
It was a while ago so I might have some of this wrong, but what I think
I remember was most of those ttl to rs232 level-shifter chips don't have
3 channels, and so you can't handle all 3 lines that the three
transistors handle, you wouldn't get DSR/DTR. And most of them also need
auxiliary caps for the charge pump to parasite power from the rs232
lines which do not actually deliver any power to speak of. There are
special ones that have their own caps built in, and there are special
ones with more channels, or you could use multiple regular ones. So, you
might only be trading 3 transistors for a max232 and two caps, or a big
expensive special max232 etc.
I still wouldn't mind tryng it just for the heck of it. The result would
be a cable that should be more technically correct, and so and more
reliable, when used with other random generic serial ports besides the
one on a model 100-200, yet still work perfectly on a model 100-200
(which has pullup resistors, which the original tpdd cable circuit banks
on).
But I don't think the result would be any cheaper or simpler to make.
--
bkw
On 7/17/19 10:59 AM, Kurt McCullum wrote:
> Brian,
>
> I noticed you have a new DB25 PCB on Osh Park. I suspect the whole
> TPDD cable was intended to take a TTL level floppy drive and bring it
> to a standard RS-232 level. I'm wondering if that same PCB could be
> used with one of the inexpensive TTL level FTDI USB to serial
> converters to create a PC to Model-T cable? The only problem I see is
> that the TTL level FTDI cables are all 6 wire and don't seem to have
> the DTR wire. But I suspect that could be hard wired some how.
>
> Kurt
>
> On Wed, Jul 10, 2019, at 11:28 PM, Brian K. White wrote:
>> I finally did the version of this that I had envisioned.
>> https://oshpark.com/shared_projects/Sk27mJwq
>>
>
