[GreenKeys] The last days of the serial terminal

[Harold Hallikainen]

That's great! As I've mentioned previously, I used a Lear Siegler ADM-1
terminal in the early 1970s. It had a huge circuit board filled with small
scale ICs. I'm amazed they got it to work. I used the ADM-1 in a product
for radio stations (program logging system at
http://bh.hallikainen.org/wiki/index.php?pagename=HallikainenAndFriends ).
The program logging system eventually went to a less expensive terminal
whose name I don't remember. I also used the ADM-1 with a home brewed Bel
103 modem using XR2206 and XR2211 to talk to the Source time share
service.There I wrote assembly language 6800 code for my wire wrapped 6802
system. I'd download the hex file into a Sunrise Electronics EPROM
programmer, burn a chip, plug it in and try to figure out why stuff did
not work. Eventually it did. I still remember some of the MC6800 op codes
such as BD for gosub and 7E for jump. I got good at counting forwards and
backwards in hex for hand assembling branch instructions.

I later used a Fluke touchscreen terminal in a broadcast transmitter
remote control system for a network in Kansas. On the home screen, there
was a button for each site. The button would flash if there was an issue
at the site. The user could then touch the button to get a detailed view
of the site with "lit buttons" to control all the equipment there. This
was all done in Basic on the system I designed with communications with
the terminal at 9.6 kbps over RS232. To give the user feedback that stuff
was happening, the terminal would beep when an area was touched. My code
then sent a beep when the command was received. That way you could tell
stuff was working.

It was a fun project! Intersite communications was Bell 202 AFSK over UHF
radios. Since the FCC required CW ID on the radios, I wrote an ASCII to
Morse routine that would send the CW ID.

All this stuff was written on a Cromemco CP/M computer with 6800
crossassembler. Eventually I got a DOS 286 machine and ran Z80MU to
emulate CP/M on it. Z80MU also ran DBASE 2 which handled our inventory
control system. I still have that computer in the garage. Need to power it
up some day. The Cromemco had a Z19 terminal connected to it. I used
Dasoft software under CP/M to do schematic capture and board layout. Both
the schematic and PCB used graphics characters on the Z19 terminal. The
schematic and PCB were then plotted on a Houston Instruments plotter. I
still have that plotter in the garage.

So... ham radio RTTY got me into FSK data transmission which I then used
for the rest of my career (most recently for the closed caption equipment
at https://www.qsc.com/cinema/products/accessibility-solutions/ which uses
10 kbps FSK over IR to carry four languages of closed captions in movie
theaters).

Harold
https://w6iwi.org






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