Visicom Textphone Reverse-engineering

b/Hardware publicado por u/Keoni29 November 17, 2014, 10:39:48 PM

Visicom Textphone Reverse-engineering

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

.

Using javascript I made all addresses operands links so you can jump by clicking them.

Last Edit: November 17, 2014, 10:42:24 PM by keoni29

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u/novenary November 17, 2014, 11:37:24 PM

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

u/pimathbrainiac November 18, 2014, 12:58:24 AM

That is awesome! Is the textphone protocol proprietary, or is it a standard protocol? If it is proprietary, will you reverse engineer it?

u/Dream of Omnimaga November 18, 2014, 03:16:50 AM

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

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

u/aetios November 18, 2014, 12:22:53 PM

Only €10 gives you a bunch of fun~

u/novenary November 18, 2014, 01:41:28 PM

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

Apparently. Also SMS exists ever since mobile phones do.

u/Keoni29 November 18, 2014, 06:26:59 PM

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.

u/novenary November 18, 2014, 07:11:54 PM

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

u/Dream of Omnimaga 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~

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.

u/novenary November 19, 2014, 06:25:26 PM

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~
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.

u/Dream of Omnimaga November 19, 2014, 11:38:01 PM

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 >.<

Last Edit: November 19, 2014, 11:41:18 PM by DJ Omnimaga

u/novenary November 19, 2014, 11:44:23 PM

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

u/aetios November 20, 2014, 11:16:01 AM

Mostly, yes

u/Duke "Tape" Eiyeron November 25, 2014, 10:02:18 AM

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!

u/Keoni29 November 25, 2014, 07:48:30 PM

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