old televideo terminal interfacing. any early 80s computer people out there?

[blackbeard]

so i recently got this from ebay. the thing came wrecked but after a ton of time i managed to at least get the electronics working as well as the monitor. it's a televideo 920c and it interfaces to a pc through an rs232 port through a db25 connector so i have no idea how i'm supposed to connect to the damn thing without an adapter. assuming i get that how do i send and receive information? is there any way to make it interface with something like a VB program to control software on my computer? anyway shoot me some ideas.

[waltr]

Well build a DB25 to DB9 (or USB) adapter. Wiki has pin-outs for the common RS232 connector pin-outs. You'll need to experiment with finding out the Baud rate. Or check with a local store that sells used computers for an adapter. I have at least one somewhere. They did come with serial cards when the DB9 for serial was rather new.

That is the basic Dumb Terminal. I used them back in the '70s and '80s to interface with mainframes.
I don't know of any method to use on to control a PC. Maybe if the PC is running DOS. There could be some programs out there to allow you to run 'command line' apps on the PC.

Good luck and have fun.

[Webbot]

As I'm sure you know: the DB25 connection just had 'so many' unused pins that they shrunk it into DB9. The only pins anything gives a damn about is: gnd, tx, rx, cts, rts. And the cts/rts pins are only needed for hardware handshaking. Google it

So what can you use the terminal for?

1. Connect the gnd, rx pins of the terminal to the gnd,tx pins of the Axon and its a terminal emulator. ie shows all uart output from the Axon. You need to disable any hardware handshake on the terminal

2. Can you use it to run a program in Windows? no. coz windows only has one user (kbd/scn) and your screen is probably char based anyway (ie no graphics)

So 'be happy' to just use it as a replacement for the usual laptop+terminal software - ie point 1 above

[billhowl]

1. Connect the gnd, rx pins of the terminal to the gnd,tx pins of the Axon and its a terminal emulator. ie shows all uart output from the Axon. You need to disable any hardware handshake on the terminal

Don't connect to Axon without level convertion, the output is +/-15V RS232 signal, this can damage your Axon if you connect directly.

[dunk]

one more useful term for your Googling:
the name of the cable to connect 2 terminal serial ports is a "Null Modem" cable.
(if you were connecting a terminal to a modem it would be a "Straight" cable.)

as for the usefulness of the terminal,
if you run any sort of Linux or Unix a dumb terminal can be connected to a serial port on the computer and used as a fully functional text console.
you would run the "getty" program on the serial port from the "innitab" file at boot time if i remember correctly then you should be prompted for username and password at boot time.


dunk.

[blackbeard]

Thanks for the info thus far. I found the manual and found that there is a dip switch for baud.   The manual says it's a "smart" terminal And I'm not entirely clear on what seperates a dumb terminal from a smart one. Does terminals send and receive information as hex?

[waltr]

If I remember correctly a 'smart' terminal can do some sorts of on screen manipulation mainly for text editing and accept commands like place cursor at x,y. Info should be in the manual.

Almost all of the terminals used ASCII encoded characters and commands (Extended ASCII). Google ASCII for the HEX values.

[Webbot]

There is a PDF manual available for download here http://vt100.net/manx/details/6,5484

[blackbeard]

There is a PDF manual available for download here http://vt100.net/manx/details/6,5484

ya i was actually lucky enough to find that too. it's looking like a nice little project!

[Soeren]

Hi,

As the manual will tell you, it was controlled wi using ESCape codes like most terminals back then.
Perhaps you can find an old IBM (PC) manual, it has tonnes of info you could no doubt use.