On 3/29/19 3:12 PM, Thomas Morehouse wrote:
Thanks John. As one end of the cable is the USB plug, and the other
is the 9 pin plug, am I correct to say I need to add the null modem
adapter to the 9 pin end?
Thanks.
Tom M.
On Fri, Mar 29, 2019 at 3:09 PM John R. Hogerhuis <[email protected]
<mailto:[email protected]>> wrote:
Yes you need a cable wired as a null modem or you need a null
modem adapter on a straight through cable.
-- John
If you have a 9-25 modem cable like this:
https://www.cablewholesale.com/products/serial-modem-cable/at-modem-cables/product-10d1-02303.php
Then you need this:
https://www.monoprice.com/product?p_id=1203
That is, a 9pin female to 9pin male null-modem-adapter. That's the
smallest, least number of adapters way, if you're using a regular modem
cable (which 99% of random unidentified 9-25 serial cables will be).
For a single cable with no adapters (aside from the usb adapter):
https://www.cdw.com/product/C2G-null-modem-cable-6-ft-white/1153481?
That is specifically that one, not random ones that look like that or
say "9 to 25 pin serial"
It has female 9pin on one end, male 25 on the other end, and is wired
null-modem inside, and includes the hardware handshaking lines.
There are a few others, but they are real uncommon because that is just
not a standard configuration at all.
More details and more tested cables:
http://tandy.wiki/Model_100_102_200_600_Serial_Cable
Possible issue:
A little while ago on the list, Kurt or Mike or someone claimed to have
problems with cables that have DSR/DTR tied to DCD when used with model 200.
I personally don't believe there is anything remotely wrong with that
configuration, and so if there is a problem, it's failing hardware or
incorrect software.
In fact I think having dcd connected is more technically correct than
not, when you are not using an actual modem which supplies an actual dcd
signal.
It tells comm software that you are "on line" and that it's ok to start
sending bytes down the line.
But, it could be. I haven't proven otherwise by experiment. So on that
page the StarTech cable is one that has all the same correct wiring, but
no DCD connection at all.
--
bkw
