null modem cable with Pi3 and TI

[Shift838]

Ok. So I am thinking that with all these Retro computers getting on line with a simple RS232 card and utilzing a Pi that we can do the same with the TI to telnet to BBS.

 

This would be another option to get online and not requiring a modem or UDS10.

 

the Pi can run the 'tcpser'to map a serial port and will respond to AT commands.

 

(I have already done this with some help on my Mist).

 

Does anyone know what the pinouts would be. I beleive it has to be a null modem cable.

 

so I need pinouts from a DB25 Male to DB9 Female.

 

Anyone have some they are willing to share so I can start testing it.

 

 

[ckoba]

It will be a straight DB25-DB9 cable. TI wired their serial ports as DCE rather than DTE (as was done with the rest of the world); in TI-land, a straight RS232 cable *is* a null-modem cable.

 

For a pinout, try this: http://lmgtfy.com/?q=serial+DB25+to+DB9+pinout

[+Ksarul]

I suspect they were stuck in the MIL-STD mode of their Government contracts. That mentality also explains the tank-like structure of the PEB and the cards they put in it (and I've even seen rare references to it in some of their internal documentation). Most military fixed communications equipment back then was either DTE or DCE, depending on where in the communications chain it was expected to operate. That way, they could use idiot-proof cables everywhere. . .so long as the hardware was connected in the right order.

Edited April 24, 2016 by Ksarul

[ckoba]

I suspect they were stuck in the MIL-STD mode of their Government contracts. That mentality also explains the tank-like structure of the PEB and the cards they put in it (and I've even seen rare references to it in some of their internal documentation). Most military fixed communications equipment back then was either DTE or DCE, depending on where in the communications chain it was expected to operate. That way, they could use idiot-proof cables everywhere. . .so long as the hardware was connected in the right order.

Yep, and that's why they used a DB25F for the serial connector. Stuff connected *one* way with *one* cable if it was going to be used in my particular segment of the service, period. I suspect that the PEB's RS232 card design was described to the GSA as a mainframe connection mechanism, which would mandate DCE. The Pr1me-100 that we *still* had running was DTE.

 

(I left that out of my initial reponse because, well, TMI )

[Shift838]

so I did a straight cable as follows but no go. did I miss something? With the below wiring when I issue an AT command (no echo shows), but when i press the T after the A my cursor freezes until I unplug the cable from the Pi3 USB to serial adapter. i know it's a wiring issue but not sure where.

 

DB9 DB25

 

3 2

2 3

7 4

8 5

6 6

5 7

1 8

4 20

Edited April 24, 2016 by Cschneider

[ckoba]

so I did a straight cable as follows but no go. did I miss something? With the below wiring when I issue an AT command (no echo shows), but when i press the T after the A my cursor freezes until I unplug the cable from the Pi3 USB to serial adapter. i know it's a wiring issue but not sure where.

 

DB9 DB25

 

3 2

2 3

7 4

8 5

6 6

5 7

1 8

4 20

That's the right wiring, except you might want to run a wire from DB9(9) to DB25(22) for the sake of completeness. I assume you read the little numbers on the connectors and are absolutely sure that you're soldering to DB9(1) instead of DB9(5) -- I often make that mistake.

 

I used tcpser awhile back on the Commodore side, and it was rather picky about command-line argument order.

 

Test with a terminal emulator on each end, don't jump straight to tcpser. If you're looking at tcpser, then you're probably running some form of UNIX, so fire up minicom on the server side (setting it to 1200/8N1, no hardware nor software handshaking) and telco on the TI side. Type a bunch of stuff on both keyboards. If you see things on both screens, then your cable is just fine, and you'll need to reread Jim Brain's docs on tcpser.

 

If you don't see anything, just get a bog-standard DB9-to-DB25 straight cable at your local PC store. You don't need to build it, it isn't fancy wiring, and you eliminate the possibility of it being a cable problem right out of the gate.

Edited April 24, 2016 by ckoba

[Shift838]

my sight is not what is used to be but I believe the back of the db 9 (solder side) if looking at it is

 

1 2 3 4 5

6 7 8 9

 

Correct ?

Edited April 24, 2016 by Cschneider

[+Lee Stewart]

my sight is not what is used to be but I believe the back of the db 9 (solder side) if looking at it is

 

1 2 3 4 5

6 7 8 9

 

Correct ?

 

Yes, for female. Backwards for male.

 

...lee

[Shift838]

ok. i got it figured out and THANK YOU all for your help.

 

the the cable was wired perfectly. the issue I had was connecting the DTR line. that is what was causing the cursor to freeze for some reason.

 

Once I disconnected the DTR line I was able to connect to telnet BBS' via the tcpser on the Raspberry Pi3.

 

a good thing is that the Pi3 now servers as a tcp server for my Mist for both Atari and Amiga cores and now the TI.

 

Another good thing is you don't have to remember the IP addresses you can use the DNS friendly name URL's!

 

i'll get something typed up.

 

it will be another option for TI'ers to get online..

[ckoba]

(removed: you fixed it. Completely forgot that TI pulled DTR high with that resistor

Edited April 24, 2016 by ckoba