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Visicom Textphone Reverse-engineering

Started by Keoni29, November 17, 2014, 10:39:48 pm

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Keoni29

November 17, 2014, 10:39:48 pm Last Edit: November 17, 2014, 10:42:24 pm by keoni29
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: http://8times8.eeems.me:81/project/software/visicom/


The built in keyboard.

Guts

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.

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 even though I don't know Golang :P.

Using javascript I made all addresses operands links so you can jump by clicking them.
If you like my work, why not give me an internet?

Streetwalrus

Wow nice, I think we have our official hardware hacker already up and running ! :D

pimathbrainiac

That is awesome! Is the textphone protocol proprietary, or is it a standard protocol? If it is proprietary, will you reverse engineer it?
Well, I'm bach here too!

DJ Omnimaga

So they had some form of SMS way back in the 80's? Nice :P

Seriously though it's fun to see old hardware like this and knowing you do a lot of modding, I am interested to see what you will do with this ;)

aeTIos

ceci n'est pas une signature

Streetwalrus

Quote from: DJ Omnimaga on November 18, 2014, 03:16:50 am
So they had some form of SMS way back in the 80's? Nice :P

Apparently. Also SMS exists ever since mobile phones do. :P

Keoni29

The textphone protocol is pretty straightforward. It uses dial tone sequences to transmit characters. In theory you could dial characters in by hand on a regular phone.\
More info about the textphone protocol can be found here:
http://8times8.eeems.me:81/project/software/visicom/#h8
I don't think it is proprietary.
If you like my work, why not give me an internet?

Streetwalrus

Wow, if you already reversed this much then it's amazing. O.O

DJ Omnimaga

Quote from: aeTIos on November 18, 2014, 12:22:53 pm
Only €10 gives you a bunch of fun~ :D
It depends where you live nowadays, though. If you are unable to get your parts from the same seller and combine shipping, then you're in for $10-50 shipping per part. If you need to buy from 15 different international sellers, especially from America, and you live in Canada then you're in for between $150 and $700 worth of shipping fees, in addition to possible custom clearance fees if the post office figures out that the package is not a gift.

Streetwalrus

Quote from: DJ Omnimaga on November 18, 2014, 10:13:29 pm
Quote from: aeTIos on November 18, 2014, 12:22:53 pm
Only €10 gives you a bunch of fun~ :D
It depends where you live nowadays, though. If you are unable to get your parts from the same seller and combine shipping, then you're in for $10-50 shipping per part. If you need to buy from 15 different international sellers, especially from America, and you live in Canada then you're in for between $150 and $700 worth of shipping fees, in addition to possible custom clearance fees if the post office figures out that the package is not a gift.
I know right. Shipping and custom fees are awful. <_<

DJ Omnimaga

November 19, 2014, 11:38:01 pm #10 Last Edit: November 19, 2014, 11:41:18 pm by DJ Omnimaga
This is why sometimes I prefer to use local brick and mortal stores, since I will not only get the stuff immediately if I find it, but also no shipping. On the other hand, their prices are way higher since they have to cover extra costs (employee paychecks, the rent, equipment, etc) so you might still be in for over $100 worth of parts. Also, you have taxes, while if you are lucky online, you might not pay them, plus some stores check Ebay prices to fix theirs, so if an item on Ebay is $5 + $25 shipping then the store will charge $28  >.<

Streetwalrus

Hmmm that does suck but again, Keoni's stuff is all makeshift hacks from salvaged hardware. Well, a lot of it. :P

aeTIos

ceci n'est pas une signature

Duke "Tape" Eiyeron

I'd like to be able to hack things like you do... Shame that my school classes have never leant me electronics... Your thing could be a neat tty for devices like calcs or RaspberryPi!

Keoni29

They did not teach me electronics in high-school. My profile-essay got me interested in electronics especially digital systems. (TI-nterface, remember?)
Ever since I have been into hobby electronics and reverse-engineering. If I manage to write a firmware for this thing I am sure I can use the internal modem to connect it and perhaps attached devices to the internet! They teach us Datacommunication at school this semester, so soon I will be an internet guru :P
If you like my work, why not give me an internet?

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