Project page: http://8times8.eeems.me:81/project/software/visicom/

The Visicom is a textphone for deaf people from the 80's. It has a keyboard, video output and built in modem. You could use it as a textphone using the textphone protocol or as a teletype (tty) using the built in modem.

I bought this at a thriftshop because it looked interesting.
I decided to crack it open and find out exactly what makes it tick. Detailed documentation can be found on my project page.


Guts

Left: Video output. You're greeted with a dutch menu. This image shows B&W video, but there is a switch inside the device which enables 8 color video.
Right: Rom reader device I built to dump the firmware. The disassembly can be found here: http://8times8.eeems.me:81/project/software/visicom/disassembly.php

I found an open-source disassembler written in Golang for the tms7001 microcontroller that is inside the visicom, but it was really buggy. I managed to fix a lot of the bugs. I published the disassembled rom on my website. Using javascript I made all addresses operands links so you can jump by clicking them.
Rom disassembly can be found here: http://8times8.eeems.me:81/project/software/visicom/#h2

I am now able to write my own code for the device. So far I can:
- Set up the serial clock generator.
- Control the MCU's internal I/O port.
- Use interrupts
- Read and write data over serial (using the ACIA)
- Read keystrokes from the keyboard

I solved some interrupt problems by looking at the disassembly. It seems like the people who designed this thing ran into the same problems as I did
Next I want to output characters on the screen.