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TRS-80 Model 100 communication vie DB9 to Ethernet cable advice needed

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retrotron

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May 11, 2016
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So here's my problem: I have a model 100, I have a (Arch)Linux netbook and both are connected via a DB9 to Ethernet cable where the DB9 end is plugged in the model 100, and the Ethernet end hooked to my netbook. Now here's the big question: how do I get both to communicate (as in file transfer), and what programs do I need to use? If I understand correctly, the DB9 port on the model 100 is another kind of rs232 port, right? Well... all of the instructions I googled up require me to use a nullmodem cable (or build one from scratch) and absolutely nothing about talking to the model 100 through the ethernet port. Can somebody help me out with this, preferrably with what I have? I'm a complete noob so my apologies if I sound completely clueless/oblivious. Thanks ahead :D
 
Retrotron,
You can't mix and match Ports on machines and expect to get communications working. I'd suggest unplugging that cable before you damage something
in one of your computers.

Stay with an RS-232C port to RS-232C Port. Your Linux machine should have two /dev/ttyS0 & /dev/ttyS1. You can verify if it also has the RS-232C
Hardware Port attached to your netbook. Of not, and you have a USB port, you can purchase a USB to RS-232C Adapter, as those work well with
Linux.

To locate the possible used COMM PORTS in *nix, cut and paste the following command:

Code: 
ls -l /dev/ttyS*

Notice that ttyS0 through ttyS3 are defined as shown

Code: 
crw-rw---- 1 root dialout 4, 64 2009-11-27 15:26 /dev/ttyS0
crw-rw---- 1 root dialout 4, 65 2009-11-27 15:26 /dev/ttyS1
crw-rw---- 1 root dialout 4, 66 2009-11-27 15:26 /dev/ttyS2
crw-rw---- 1 root dialout 4, 67 2009-11-27 15:26 /dev/ttyS3

User must be a member of group dialout.

Running this command will determine the Baud rate of the Port:

Code: 
stty -F /dev/ttyS5 -a

and to change it to 300:

Code: 
stty -F /dev/ttyS5 300
stty -F /dev/ttyS5 -a

If you have a DTE (Terminal versus DCE) you can connect Pin 2 (TX) to
Pin 3 (RX) to ECHO back what you transmit. You may also have to Jump
Pin 4 to 5, and Pin 6 to Pin 8 to Pin 20 to complete the NULL Modem
configuration, if it doesn't Transmit.

Code: 
echo Testing.... > /dev/ttyS5

Which proves characters were routed out to Pin 2 and back on Pin3.



Your Model 100 may have a RS-232C port attached to the DB9 connector. You will have to read up on the M-100 and then get a Null Model Cable
to test the DB9 connection.

You will also need software on both machines for the transfer of files. That might be a problem for the M-100.


Larry
 
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The M 100 has the following:

Ports: RS-232, parallel ports, bar code reader, 300 baud modem

So you are plugging into the Phone Line Jack versus an RS-232C Port.


Larry
 
You're using one of these cables, I'm guessing? As already said, unplug it before you roast something. These cables don't have any ethernet-to-serial magic inside of them, they're used to connect to (mostly) network equipment like routers and firewalls that have RS-232 ports in the form of an RJ-45 jack. Or alternatively you might plug the 9 pin end into a server computer with a standard PC serial port and the RJ-45 into a serial console equipped with that sort of port. If you have neither of these things around you should throw that cable away to avoid further confusion.

And also, as sort of noted, that 9 pin connector on the Model 100 isn't even a serial port. It was meant for a barcode reader. To talk to a PC you need a *25 pin* to 9 pin cable, appropriately wired, and on most modern computers you'll need a USB-to-Serial dongle with appropriate drivers given the scarcity of real built-in serial ports these days.
 
Scrap metal, I should have known.. Well, nothing smoked, sparked, smelled, and my model 100 seems to work just fine so I'm hoping for the best. I do have the reader pen (came with the machine) but need to find a way to test it. Back to my problem - So I do have an old Dell Latitude which has both a DB9 and DB25 serial ports (hence my false conclusion that the model 100's DB9 port was an alternative serial port), so let's say I find a standard nullmodem cable at a Goodwill, would it work as is with the DB25 serial port on the old lappy or do I still have to make a custom one myself? I have one of these phone connectors for the model 100 (the one with the 5 pin round plug and two phone cables) - could I use that? How would I establish a connection through the lappy modem's phone jack with, say for expample Putty?
 
Do be sure that the DB25 is a serial port and not a parallel or SCSI port. That poor D-sub "B" shell has been vastly overworked.

And, to be nit-picking, the 9 pin thing is in an E-sized shell, so it's a DE-9.

(I really shouldn't let this bother me--people have been calling anything in a D-subminiature shell "DB"--but it does all the same. :) )
 
Chuck(G) said:
Do be sure that the DB25 is a serial port and not a parallel or SCSI port. That poor D-sub "B" shell has been vastly overworked.

And, to be nit-picking, the 9 pin thing is in an E-sized shell, so it's a DE-9.

(I really shouldn't let this bother me--people have been calling anything in a D-subminiature shell "DB"--but it does all the same. :) )
Click to expand...

Heheh.. I'll try to remember to call it by it's real name. Something hit my mind: What if I used an DB.. er.. DE9 to DB25 adapter and used that on the 100, would that work? It would be def. cheaper to acquire, especially from the computer recycling store nearby..

PS: How about the 5 pin phone jack on the 100? As mentioned before, I have the cable for that and my old lappy has an RJ-something jack next to the ethernet port. Any idea how I can utilize that for communications, avoiding the RS232 port altogether? That would certainly save me the trouble of hunting down additional peripherals/cables.
 
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Ok, I finally found a serial cable to connect my model 100 to my old linux lappy. However, I'm still struggling a bit here though. I use Telkom and Minicom to communicate between the two, well.. except they don't. I set the serial configs to proper values on both machines, but I just can't get it going. Minicom uses /dev/ttyS0 for the serial port, so if I if I hit F4 (Term) then in theory, they should automatically connect, right? However Ctrl A-Z tells me that Minicom is offline. What am I doing wrong? This is like pulling teeth from a tasmanian devil geez...
 
I found the following information on the M100's Serial Port. I assume it is correct.

M100 (and T200) Serial Port Pinout

1 GND Ground
2 TXR Transmit data
3 RXR Receive data
4 RTS Request to send
5 CTS Clear to send
6 DSR Data Set Ready
7 GND Ground
8 - 19 No connection
20 DTR Data Terminal Ready
21 - 25 No connection

If it is in fact transmitting on Pin 2, this port is a DTE (Data Terminal Equipment)


Linux DB25 DTE Serial Port

1 GND Ground (Shell)
2 TX Transmit Data
3 RX Receive Data
4 RTS Request to Send
5 CTS Clear to Send
6 DSR Data Set Ready
7 GND Ground
8 CD Carrier Detect
20 DTR Data Terminal Ready
22 RI Ring Indicator

Liux Port is also a DTE.


Your connections should be the following for a NULL Modem

NIX M100
02------->03
03<-------02
04->| |<-04
05<-| |>-05

20->| |<-20
06<-| |->06
08<-|


Is this what you have so far?

You can unplug the M100's cable and short Pin 2 to Pin 3, then type characters from the Terminal in Linux, and they
should be repeated on the screen. Then unplug the Linux Terminal, and type on the M100 with Pins 2 & 3 shorted
together and see if characters are echoed on your display. That should prove everything is working on each end.


Larry
 
The model 100 is definitively a DTE. The test on my lappy failed miserably. When I do "stty -F /dev/ttyS0" it just hangs. I tried "echo test > /dev/ttyS0" in another terminal without success. Then again I just now noticed (and I can't believe that I didn't notice this before) that the rs232 port on my lappy is marked as a printer port. But, hasn't the rs232/printer port on older PCs/laptops been used for other purposes, including communications, as well? Are there any linux programs/drivers to make this function as a DTE? I really want to avoid going Frankenstein on that cable.

PS: I have this cable that connects to the portable disk drive. I was thinking, since one end has a rs232 plug, and the other a proprietary female plug, maybe I could make the right connections using solid core wires? What is the pinout of that cable? If it turns out that I can't use the rs232/lappy, I have a DE9 plug with solder lugs, so perhaps I could solder some wires on there and stick them in the appropiate pin holes at the floppy end of the disk cable. That way I might at least avoid butchering some perfectly good cables.
 
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A parallel printer port is not, and never has been, an RS232C serial port. Period. Don't try to use it as one as you can damage it--the parallel port is not designed to be immune to +12/-12 EIA signal levels.

The way I've handled interconnection of serial ports is with a "straight through" cable and an RS232 "jumper box". exempli gratia. In that way, I don't have to try to figure out what any cable really is--just find the appropriately-labeled jumper box and tack it on.
 
Oh, well... I guess I'll have to whip one up myself. That cable only cost me $.50 anyways but it's kind of a bummer to butcher a perfectly good cable. I have one more question though - as mentioned before, I have a modem cable for the model 100, which I could connect to my lappy's modem jack - what would stop me from using that instead? And why can't I find any instructions on how to connect to a PC/laptop that way?
 
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retrotron said:
... I just now noticed (and I can't believe that I didn't notice this before) that the rs232 port on my lappy is marked as a printer port.
Click to expand...
If it's marked as a printer port then that is almost certainly what it is; what makes you think it's an RS-232 port? Listen to Chuck ! ;-) The type of connector does NOT tell you what it is used for: the M100's DB25S is indeed its serial port whereas on your laptop the identical connector is used for the totally incompatible printer port; on the laptop the DE-9P is its serial port while the M100's DE-9S is the (again, totally incompatible) barcode port.

If you haven't already damaged any of your ports (fortunately the M100's RS-232 levels are only +/- 5V) then I'd recommend you read the manual that you can find at http://www.club100.org/ and the various articles and hints about exchanging data or logging into another computer there and also on http://bitchin100.com/

Bottom line: at a minimum you need a null-modem cable and any necessary adapters to connect the M100's DB-25S to your laptop's DE-9P; if you want to use it to log into a Linux system you'll need appropriate software and a full-null-modem cable that allows hardware handshaking because Linux does not handle the M100's native XON/XOFF handshaking very well.

All explained on the above sites.

mike
 
Back to the idea with the disk drive cable - I was thinking if the pinout of the drive end of the cable provides the necessary connections for serial communication, then I could theoretically save myself some work, butcher the DE9 to RJ45 cable and stick the wires into the pin holes of the disk cable. Hmmm.. a pinout diagram of the disk drive cable would be helpful..
 
retrotron said:
Back to the idea with the disk drive cable - I was thinking if the pinout of the drive end of the cable provides the necessary connections for serial communication, then I could theoretically save myself some work, butcher the DE9 to RJ45 cable and stick the wires into the pin holes of the disk cable. Hmmm.. a pinout diagram of the disk drive cable would be helpful..
Click to expand...
You're really determined to damage something, aren't you... the disk drive cable is not just a cable, there are active parts inside; as to a DE-9 to RJ45... :rolleyes:

Whatever... good luck with that.
 
Well I thought it would be an option since it has a RS232C end. What active parts could there possibly be inside such a cable? No pun, just being curious. And I agree, I rather leave the toasting to actual toasts :p
 
As MikeS mentioned just get a null modem cable with DB25 and DB9 on each end plus a suitab
le adapter. Hopefully that will work. With any luck you haven't already damaged a port on either of the systems.
 
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Do you mean the printer port on the back of your model 100? That's not a floppy port, it's for connecting a parallel printer, and if you have the cable, it ends in a 36 pin Centronics parallel printer connector, not serial.

If you have a Tandy Portable Disk Drive (TPDD) or TPDD 2, they do connect to the serial port on the model 100. You'll need to bootstrap in the DOS, it's not built in to the system, instructions are available here: http://www.club100.org/library/libdoc.html If you do have a TPDD, it's possible there's a TS-DOS ROM installed in your system, there are instructions on the club 100 site for that too.

Please don't cut up the TPDD cable if that's what you have, regular 9 pin female to 25 pin male serial null modem cables aren't that hard to come by, if you just want to use your model 100 as a terminal. Like this one, for $6.80: http://www.amazon.com/StarTech-com-10-Feet-Cross-Wired-Serial/dp/B00066HL50

Here's a model 100 owner's manual, enjoy and RTFM: ftp://ftp.whtech.com/club100/doc/TRS80-M100-User-Guide.pdf
 
retrotron said:
Well I thought it would be an option since it has a RS232C end. What active parts could there possibly be inside such a cable? No pun, just being curious. And I agree, I rather leave the toasting to actual toasts :p
Click to expand...
You mean a DB-25P end; whether it's full or minimal RS-232, DTE or DCE, parallel or who knows what depends on what it's intended for and plugged into. If you're going to play with funny cables the first thing you'll have to determine is which wire connects to what. The disk drive cable contains diodes or transistors and a resistor or two, effectively an RS-232<>TTL converter IIRC.
 
retrotron,
On your Linux Laptop, when you list the serial ports it shows you the permissions and group for users:

larry@debian:~$ ls -l /dev/ttyS*
crw-rw---- 1 root dialout 4, 64 May 14 16:53 /dev/ttyS0
crw-rw---- 1 root dialout 4, 65 May 14 16:53 /dev/ttyS1
crw-rw---- 1 root dialout 4, 66 May 14 16:53 /dev/ttyS2
crw-rw---- 1 root dialout 4, 67 May 14 16:53 /dev/ttyS3
larry@debian:~$

So, I have to be a member of dialout to use the Serial port.

The groups (or groups larry) command will show what groups I am a member of:
larry@debian:~$ groups
larry cdrom floppy sudo audio dip video plugdev netdev scanner bluetooth lpadmin vboxusers

To add myself to the dialout group:

useradd -G {group-name} username

useradd -G dialout larry

Now, I should have access as loggedinuser to the serial port through the Linux software.

I'd just make myself a Null Modem cable versus hacking up a good functional cable.


Larry
 
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