RS-232 Problem?

[toml_12953]

I had been using an ASR33 Teletype with my Altair Clone with no problems. Last night I hooked it up again after Wayne Durkee (He's da TTY man!)fixed the paper tape reader. Now when I start up the Altair, I get something like this (with different garbage every time):

Code: Select all

%^!!%^@ORY SI@@!^?
LINEPR@YHD@?
HIGHES43&*&@BER?
&*^@W MAN&&@#*&#$ES?
H&*@@#DOM@@LE&#@?

7342-2 BY@#@!^F#!#

OK

As you can see, some of the characters are correct (different ones every time). I have the 2SIO baud rate set to 110 and I've tried various combinations of CTS and DTR with no change. The manual says there's a way to disable CTS and DTR but I don't see that choice in the EPROM setup menu (version 1.81). I tried disabling RTC interrupts and the Turnkey ROM. No change with those disabled, either. I also tried booting with the sense switches set to 1 and 2 stop bits (The TTY uses 2). This is really bugging me! I can use the TTY with my Lubuntu box with no problem at all so I'm pretty sure it's OK. I can use the Altair with a 9600 bps dumb terminal with no problems also so I think the 2SIO is OK. Can anyone shed some light on this? Thanks for any insights!

Tom L

[AltairClone]

I can duplicate your symptoms if I run with one stop bit instead of two. Are you setting A15-A12 (leftmost four switches) to zero before depressing run?

Mike

[toml_12953]

I can duplicate your symptoms if I run with one stop bit instead of two. Are you setting A15-A12 (leftmost four switches) to zero before depressing run?

Mike

Yes, I am. I've tried both one and two stop bits with the same results. When I boot from the turnkey module, I have all switches down when I turn on the machine.

[AltairClone]

Since I can generate similar symptoms when running with one stop bit, it sounds like you may be running up against framing errors. It's not going to be anything to do with CTS, RTS, etc. Sounds like it's time to bring out a scope.

I assume this is the same RS-232 to current loop adapter you were using previously? The Altair Clone uses fairly low RS-232 voltage levels (less than +/-5v), so it may be you've been running on the hairy edge of working with your adapter, and now things have moved just a fraction to the not-working side of that hairy edge.

Mike

[toml_12953]

I assume this is the same RS-232 to current loop adapter you were using previously? The Altair Clone uses fairly low RS-232 voltage levels (less than +/-5v), so it may be you've been running on the hairy edge of working with your adapter, and now things have moved just a fraction to the not-working side of that hairy edge.

Mike

You're right again, Mike!
I don't know if you remember but I had TWO power supplies on my converter when I found out the Clone didn't provide enough voltage to supply the interface. Back then you recommended I eliminate one and tap the one supply for both sides of the interface. Since it was working, I didn't take your advice and left it alone. Now, since you mentioned the voltage again, I measured the output of both AC adapters. One was fine at 12v, the other was 0.
I finally took your advice and am now using just the one supply and it works like a dream. Thanks again for your help and patience. I promise to follow your advice in the future even if I don't see the need for it immediately! :) Seriously, I do want to thank you for making such a fine piece of hardware and for your continued involvement with and support for your customers. I'm sure everyone who bought a Clone from you appreciates you as I do.

[AltairClone]

Glad to hear you're up and running again!

I'm very glad to be involved and help. Sad to say, this is the most exciting part of my life :)

Mike

[waltermixxx]

Add some excitement, Come to the midwest vintage computer festival in Elk Grove ILL. this weekend :)

I'm going, it will be my first time going to such an event ( been to many world of commodore meetings in toronto ) but first time going to one not centered on a particular machine)... :) Very excited. :) I have wallet sized photo's of my Altair Clone to show folks... (talk about old school :) )

Cheers. :)