[GreenKeys] Model 43 and Altair 8800

[Paul Wills (CKT&T)]

Jon,

It sounds, to me, like it's coming from the computer end.  The computer 
is echoing the character you typed.  I had that problem with my CP/M 
computer years ago and ended up writing a driver that would "eat" the 
next outgoing character if it matched the last incoming character.

Hopefully, you can find an easier way.

PDW

On 9/30/2024 2:10 AM, Del Rey Custom Shop wrote:
> Hi, new to the list...and wondering if anyone has any ideas about an 
> issue I'm having with a Model 43 KSR with TTL board, hooked up to an 
> S-100 computer, in this case a Vector Graphic, from the laste 70's.
>
> I am going through a DB25 null modem, so handshaking is there along 
> with the correct pin assignments, yada yada. The Altair correctly 
> prints out the monitor prompts to the Model 43 and I'm able to issue 
> commands to it from the Teletype, as well as receive back the correct 
> data. The data received back from the computer looks fine and 
> characters aren't doubled.
> A problem arises when I type in commands from the 43. Characters are 
> repeated, eg, typing 1234 will yield 11223344. I'm not sure what is 
> causing this.
>
> An interesting thing is that when I communicate to my PC's terminal 
> program, from the 43, the doubling of characters doesn't occur. On 
> that I have it set to 7 data bits, Even parity, 1 stop bits.
>
> Currently, both machines are set to 300 baud. On the 43 I have Parity 
> Off and on Full Duplex. I'm not sure if the problem is on the computer 
> or Teletype side.
>
> Thanks for your input,
> Jon
>
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