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Apple ][c, tcpser, and 1200 baud

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Divarin

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Mar 9, 2019
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Location
Cleveland, OH
I have an Apple ][c and I have been using it with TcpSer running on a nearby PC connected over a serial cable. I've been using various term programs to BBS. The term program I normally use is Apple Term which only supports 300 and 1200 baud. A few weeks ago for no apparent reason it stopped working at 1200 baud but would still work at 300.

By "not working" I mean you type in characters like "AT" and you get a strange characters back.

I have no updated my copy of tcpser or changed the terminal settings on the apple. I also tried some other terminal programs such as Proterm. In proterm I also was able to set higher baud rates so I tried 2400 and 9600 both with the same results.

When using ADTPro I can still transfer data over from PC to Apple at 57600 baud without any issues. I also tried connecting the pc through the same usb to 9-pin adapter to another neaby PC running dos and it can communicate at 1200 or any other baud rate just fine.

I'm kind of at a loss as to what could cause this or what I could investigate next. If it wasn't for the fact that ADTPro is working fine I would say it's the serial cable going into the apple.

I also tried 110 baud just to see what would happen that is working as well so it looks like anything above 300 is not working in any terminal programs I have but is working through ADTPro.
 
brake in the cable or modem fault are the two big things that jump to mind. If you want to test your serial card (internal IIC serial) use adt pro and specify different connection speeds and see how it works out.
 
okay. the only other speed ADTPro would let me specify is 19200 so I tried that (which is also one I had tried in proterm) it works fine in ADTPro, slower of course but no issues.
 
looking a little closer at what's going on when at 2400 baud (just to pick a baud rate at random, though the behavior above 300 baud is the same). it's not exactly garbage characters it's either one of two characters. ether pipe | or backtick ` and it's consistent when I press a key that key will either echo back a | or a ` always.
I added an input trace on tcpser and it shows that it's always getting:
RS<-|0000|ff
regardless of whether the echo is | or `
 
VERAULT said:
Does it support 600 baud?
Click to expand...

No, at least none of the term programs I have do.

To try to narrow down the culprit I decided to take the PC out of the loop and instead connect to two different devices: one is a raspberry pi which auto-runs tcpser on startup (I had been using this on another computer but now it's just sitting on the shelf unused) and also a stand-alone wifi232 device. both are configured for 9600 baud.
In both cases I can't get it to work but the behavior is different. With the PI I get garbage characters (not the same | and ` that I get when connected to my PC) and with the wifi232 device I get nothing at all, no echo.

I connected these two devices to my dos box (a pentium-2) to confirm that they are working, I can communicate at 9600 baud that way.

There is one other piece of the puzzle: Not too long ago (probably around the same time actually) the 9pin to usb adapter I was using just up and died, like windows just doesn't even see it anymore. I swapped it out with another one I had lying around and that's what I've been using. This is the same adapter I use on the dos box when I'm BBSing with that (which I have no issues with even at 57,600). But anyway just to try to rule out that adapter I took the apple's serial cable and plugged the 9pin side of it into the com port on my dos box.

I loaded term programs on both machines and matched the baud rate. I found that at 1200 baud anything I type on the apple would make it over to the pc just fine but nothing I typed on the pc appeared on the apple. I also found that I couldn't establish a connection at a higher baud rate.

If ADTPro wasn't working (or was flaky) I'd say it's definitely a bad cable or something wrong with the apple but the fact is ADTPro is working just fine which I can't explain.
 
Could it be that there is a failed component in the modem? Capacitor, resistor etc. Over 20 years ago when I was a service technician I would get so many systems that were fried from lightning/thunderstorm damage every summer. The massive surge would enter via the modem and usually burn up other things as well. My point is some of the modems still seemed like they were partially working even with bad components.
 
VERAULT said:
Could it be that there is a failed component in the modem?
Click to expand...

It doesn't sound like there is a modem. OP said they are using tcpser which is a program you run on a modern computer with a serial port and it pretends to be a modem. So I'm pretty sure this is a direct serial connection, null modem.
 
jafir said:
It doesn't sound like there is a modem. OP said they are using tcpser which is a program you run on a modern computer with a serial port and it pretends to be a modem. So I'm pretty sure this is a direct serial connection, null modem.
Click to expand...

That's right.
 
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