Why does this sort of thing bother you? Why do you feel it's so important to insist that the term 'null-modem' is only valid if the modems it replaces are both RS-232 and not if one of them is a USB modem? A modem is a modem (although technically the box that connects your computer to the internet may not be a modem, something else for you to rant about ;-) )
I certainly had much better results googling for "USB serial null modem" than "USB Provides a DB25M wired as DCE"... If Tripp-Lite calls their U209-18N-NULL cable a "USB to Null Modem Serial FTDI Adapter Cable" (and most people who've never heard of DTE or DCE know what that is) then I'd say that there is such a thing, despite the fact that you "know better" and don't want to use the term. https://www.tripplite.com/usb-null-modem-serial-ftdi-adapter-cable-com-retention-usb-a-db9-m-f-18in~U20918NNULL IMO you should have put it all under "opinion". Or are you really just trolling? ----- Original Message ----- From: "Brian K. White" <[email protected]> To: <[email protected]> Sent: Friday, May 31, 2019 2:19 PM Subject: Re: [M100] possibly ideal serial cable? > It's no great mystery that web sites, who wish to sell things, employ as > many keywords as possible so that even uneducated people who search for > things by the wrong terms can still find them and buy them. > > That doesn't make the term any less incorrect, nor does it mean anyone > else, in any other context (meaning me, and here), should use the wrong > terms for things if they know better and don't want to. > -- > bkw > > On 5/31/19 1:51 PM, Mike Stein wrote: >> >> For something that "there's no such thing as", there sure are a lot of >> various null-modem adapters and cables out there. >> BTW, while we're picking nits, USB/is/ a serial protocol, so a >> USB<>RS-232 adapter /does/ have two serial ports! >> As the name suggests, a null-modem cable/adapter/whatever /replaces >> a serial modem-to-modem/ connection between two computers regardless >> of the protocol used; RS-232 and RS-232 modems have been obsolete for >> decades, so the term 'crossover' has become more popular, but it's the >> same thing: a cable or adapter to directly connect two computers together. >> A pair of modems would connect the transmit signal (pin 2 on an M100) >> on one end to the receive pin (pin 3) on the other end. When you >> replace those 2 modems (RS-232, USB, whatever) with a null-modem cable >> you emulate those modems and do the same thing, connect transmit to >> receive etc. (instead of straight-through, connecting transmit to >> transmit etc.) >> Good luck in your quest to eliminate the term "null modem" in >> reference to USB cables; I suspect it'll be around for a while and >> more easily understood by many folks than "Provides a DB25M wired as DCE" >> FWIW, here's a USB-RS-232 Null modem cable; better send them an email >> to let them know that "there's no such thing" ;-) : >> https://www.startech.com/ca/Cards-Adapters/Serial-Cards-Adapters/USB-to-Null-Modem-RS232-DB9-Serial-Adapter-Cable-DCE-FTDI~ICUSB232FTN >> Here's an example of a USB-USB null-modem RS-232 replacement; DTE and >> DCE have no meaning here whatsoever. >> https://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_USBNMC.pdf >> And here's an Ethernet null-modem (crossover) cable: >> http://www.nullmodem.com/10BaseT-Crossover.htm >> m >> ---- Original Message ----- >> >> *From:* Brian White <mailto:[email protected]> >> *To:* [email protected] <mailto:[email protected]> >> *Sent:* Friday, May 31, 2019 5:56 AM >> *Subject:* Re: [M100] possibly ideal serial cable? >> >> Technicality: >> >> There's really no such thing as null-modem in a usb adapter. >> Null-modem vs straight through describes the wiring between two >> serial ports. A usb adapter only has one serial port. >> >> That single serial port can be wired to be either a DCE port or a >> DTE port. Most computers or host devices (like terminals) have DTE >> ports, and most peripherals (like modems) have DCE ports, so that >> a modem can connect to a terminal with a simple straight-through >> cable. >> >> Most usb adapters are meant to drop in place of the serial ports >> that computers no longer have, and so they provide a DTE port. >> >> A custom non-standard one could provide a DCE port instead, and >> could be made even more non-standard by having a DCE port with a >> female connector. >> >> So, it's not null-modem, but it is "Provides a DB25M wired as DCE" >> >> ------ >> >> Opinion: >> >> I personally wouldn't like to combine the serial cable and the usb >> adapter in one, especially not if the serial port will be so >> unusual. I don't like uneccessary adapters and connection points, >> but I do like standard interfaces. So there is a tug of war or a >> balance between those two aims. I like the usb part to be >> generically useful on it's own with anything else, and if the usb >> part breaks, you can swap in any other standard usb adapter. Same >> for the serial cable. It doesn't have a chip that could go poof, >> but a wire or a pin could just break. If it's a standard cable, it >> can be replaced with any other standard cable. >> >> I also don't like adapters hanging off of device ports directly. >> I'd rather have the rigid plug that sticks out of a usb port or a >> serial port be as small as possible. Aside from being generally >> less annoying, it puts the least mechanical strain on the port, >> and reduces the chance that you'll break the usb or serial port in >> your laptop or other device. So if I have to use adapters, I try >> to use a standard cable on each device, and stick any adapters in >> cabling in the middle. Although, those mini adapters that are just >> like two plugs back to back, a single one of those on an existing >> plug isn't *too* bad. >> >> I also don't like relying on things that are too custom that you >> couldn't find from other sources or 15 years later. >> >> But I myself spent some time hunting down the ususual "ideal" >> serial cables to document on tandy.wiwk, so that you could have a >> serial cable that had everything but the usb all in a single cable >> with no adapters. Partly for the neatness and convenience, and >> also to document something that a new user could buy and it "just >> works" even if they have no idea how rs232 works. Those cables are >> off-the shelf, not made custom by a single person, but they are >> still non-standard cables that are really only good for this one job. >> >> So, I'm guilty of violating that "standard interfaces" rule a >> little myself, because those cables look like modem cables but >> they're not. The really ideal minimal as possible arrangement, yet >> that maintains all standard parts and interfaces all the way, is a >> standard 9-25 modem cable, a standard usb adapter, and a 9m/9f >> mini null-modem adapter in the middle. (Except I think no one >> makes one of those mini-null modems with complete wiring, while >> some of the cables I found are more complete.) >> >> I have to admit, for the purposes of simplicity and removing all >> the variables that people are mystified by... this does remove all >> opportunities to get anything wrong, and makes the smallest and >> simplest object to include in a laptop bag along with the M100. It >> only does one thing, but if you're only doing this one thing, this >> is the simplest way to do it. >> >> I would put a label right on the plug that says For Model 100 >> though if I got one. Or at least one that says Port is DCE or >> something. >> >> It's bad to have objects lying around that look like one thing, >> but are actually something else. If I didn't know the extremely >> bizarre special purpose this object was wired for (let's say I'm a >> young relative 10 years from now) and I came across it in a box of >> junk, and tried to use it, it wouldn't work, I'd watse time >> spinning my wheels trying things that *should* work, and then >> throw the thing away. Or I'd stumble upon some combination of >> adapters that worked, and then I'd think I leaned how serial ports >> worked except what I learned wouldn't work anywhere else. (and >> then if I somehow ever found out out that it wasn't broken, it was >> just wired up in an insane way, I would curse whoever made it, and >> whoever didn't put big explanatory labels all over it). >> >> All that said, it's a cool find and I'll probably get one! >> >> For an example of what I mean about not combining too much... >> >> Say you don't buy into any of that nonsense I just bloviated so >> much about, and you like this all-in-one cable because, duh, look >> how slick that is! Right from the laptop to the m100 in one shot! >> >> Now you want to use mComm on your phone instead Laddie on your laptop. >> >> Now what? You need... an adapter. You need an "otg" usb adapter to >> go from the phones usb-c or micro-usb to provide a usb-a port. Do >> you really want to go back to that guy on ebay and have him make >> another special cable with a micro-usb on the end instead of >> usb-a? If not, why not? What was the point of getting this custom >> cable in the first place? >> >> And then next year when you get a new laptop that only has usb-c >> ports. You need an adapter again, or you need yet another custom >> cable whose only difference is a usb-c plug on the end... >> >> Maybe I won't get one after all because both those last two >> examples are already true for me. I have an android phone and an >> android tablet with only a micro-usb. My next phone will probably >> have usb-c. I already have old and new laptops with both usb-a and >> usb-c, including one with only a single usb-c port. >> >> -- >> bkw >> >> On Thu, May 30, 2019, 4:38 PM Jim Anderson <[email protected] >> <mailto:[email protected]>> wrote: >> >> I ran across this eBay seller while looking for ham radio >> programming cables for my various radios - the seller is a ham >> and makes custom serial programming cables for hundreds of >> varieties of radios. I did not think to look deeply at his >> inventory when placing my order with him, but it occurred to >> me today that he might also make different varieties of >> regular DB-9 and DB-25 based USB serial cables, and what do >> you know, he does! >> >> One of the cables seems like it might be perfect for our hobby >> - USB with an FTDI chip on one end, DB-25 male wired null with >> full handshaking on the other end, and what seems to be a >> fairly thin and flexible cable in between. The only downsides >> are that it's a bit pricey ($37 US) and that the DB-25 >> connector shell he uses may be too bulky to properly fit a >> Model 100 without cutting extra clearance on the connector >> shell or the M100 housing (this is a known problem with some >> cables and the 100, but doesn't affect the 102 or 200). Also >> AFAIK he only sells on eBay, not through other retailers, >> which may be a problem for some people. >> >> >> https://www.ebay.com/itm/FTDI-USB-DB-25-Male-Serial-RS-232C-Null-Modem-Full-Han >> dshake-Cable-NM-25M/151495441948 >> >> <https://www.ebay.com/itm/FTDI-USB-DB-25-Male-Serial-RS-232C-Null-Modem-Full-Handshake-Cable-NM-25M/151495441948> >> >> http://tinyurl.com/y3wln2l3 >> >> I really wish I'd bought one while I was ordering cables from >> him, even just to try it out (it would have been cheaper >> because shipping to Canada is $$$ and I was getting three >> cables sent already for the shipping price of one). If I have >> a reason to buy anything else from this guy I'll definitely >> get one of these and give it a whirl if nobody else has tried >> and vetoed it by then. >> >> >> >> >> >> >> >> jim >> >
