This thread wasn't systematic from day1. Can we blame it on overworked and tired. It seems like Les and I were getting confused.
I was hoping initially for:
(Voltages relative to pin 5)
1
2
3
4
5
6
7
8
9
Similar voltages at the PC end, would have helped too.
Didn't realize you were breaking the cables in the middle and making connections.
Anyway, you got it. I just thin we could have gotten to the end point sooner.
The manual is the first line of defense. The breakout box is the second.
Measuring voltages is an ersatz breakout box. The reason why it helps is that you can't have voltage on the same pin on both sides.
Now write this cable information up (M,F) and put it somewhere - including here. Include the baud (9600), flow (Hardware), Data (), Stop bit() info.
So, yep there's a 9-pin connector of the "wrong" gender on the plotter.
"Wrong" is relative with RS-232.
The "good news" is that with RS-232 switching wires haphazardly won't screw things up. At least for the 9-pin version.
Note here:
https://www.arcelect.com/rs232.htm
under V.24/RS232 Interface nearly all of the signals on the 25 pin connector are used. They were even nice enough to provide test signals.
My two worst RS-232 issues were:
1. A Macintosh (RS-422) talking to an RS-232 motion controller. I had to introduce a better driver.
2. The RS-232 Driver chips kept blowing up on an X-ray diffraction machine. I had to add isolators.
I did work in the era when Bell (the telephone company) owned the modems.
18 alerts this morning. A record. It's great that Les and I are on opposite sides of the big pond. We often find that we complement each other. Thanks Les. I was about ready to throw in the towel out of frustration.