Problem diagnosing through serial cable (Techstep style)

[BL!]

Hi!

I was thinking of testing out a serial cable in order to be able to diagnose motherboards when needed (inspired by the video Adrian Black posted a while ago). Using ZTerm on the Macintosh side and Tera Term on the PC/Windows side to verify the connection first. Adjusted the settings the same way Techstep is supposed to be communicating (9600/8/N/2 (and no flow control)) and I can write text and receive text without issues. When booting the Macintosh and pressing the NMI switch it seems "OK" until I start to type characters on the Windows side, then the Macintosh starts to output continuous junk on the screen. While testing this multiple times I've been able to see that the junk can contain the identifier string for the model. I've attached some screenshots if anyone here has a clue of what might be wrong? I mean communication obviously is working with the terminal programs so the cable must be correct I guess?

Tera Term - received text from the Macintosh:


ZTerm - received text from PC/Windows:


Garbled data received (managed to send *A and *5 so the identifier can be seen on every iteration of trash) and which also means that the data sent the Macintosh is correct since it accepts and execute the commands:

 

[robin-fo]

It‘s probably not tho only problem, but you need to correctly set the line ending character in TeraTerm. Try CR.

 

[BL!]

Thanks but it's already set to CR (tried setting it to different settings as well).

 

[adespoton]

Which VT emulator setting are you using on both ends?

 

[BL!]

In ZTerm I didn't choose anything apart from speed, stopbits, handshaking etc. and in Tera Term I think it's set to VT100 by default. But when in diag mode you cannot choose anything on the Macintosh side, it is what it is.

 

[adespoton]

Right; it's probably something that diag is emitting that VT100 is misinterpreting; might want to try a different terminal on the Tera Term side.

 

[BL!]

Well, Adrian Black is using Tera Term in his demonstration video so I have to assume it's working. I think the only mentioned thing apart from baud rate, stopbits etc. is a slight delay on character transmits. Below screenshot is from Adrians video (he sets the transmit delay to 1 msec/char). Other than the below I cannot see that he sets up Tera Term in any unique/special way at least.

 

[nathall]

I think he means try a different terminal emulation (ie, something other than VT100).

 

[Mk.558]

This makes me wonder if we can make software TechStep equivalent.

 

[BL!]

This makes me wonder if we can make software TechStep equivalent.

I was thinking the same. I don't know how Techstep operates and looks "IRL" but a GUI similar to that would be nice.

 

[Mk.558]

Could ask the guy who made modern replicas.