Mike_Z
Veteran Member
A few years ago, I acquired a Friden Flexowriter SFD-V. After a year or so, doing a lot of cleaning, adjustments and replacing the drive platen, my Friden is working. I would like to connect the Friden to my older computers. I started out by making a level converter. The Friden logic uses 100 Volts DC and only has contacts and magnet coils. Next I made a Raspberry PI to convert the Friden code to ASCII code. The Friden is a 1959 machine, from some of my reading ASCII code was not used until the early 1960's. Anyway, I have successfully made a circuit that will take a RS232 signal, supply that to the Raspberry PI, which converts the ASCII to Friden code and finally convert the logic levels from 5 volts to 100 Volts for the Friden.
My first problem is that the Friden Code does not have many of the ASCII codes, but I think I can get around that. For example there is no ESCAPE code or exclamation point. The exclamation point can be printed, using an Apostrophe, backspace, period. The Friden code contains many punch tape/card control characters some of which are actual keys on the key board. I think I can just convert some of these keys in the PI code conversion.
The second problem is whenever a key is pressed, the Friden code is sent to the PI AND the typing machine will independently print that character. If I connect this circuit to the RS232 comm port of my DEC PDP8E, a key press, the Friden will print the character and the PDP8E will send back that character. The key pressed character will be typed twice.. I'm a little confused on how the Friden could be used as a terminal with any computer that has a full duplex comm port, as the PDP8E. There is no way to stop the Friden from typing a character when a key is pressed. Is there a way to convert the comm port or operating system to half duplex? If that can not be done, I suppose the Friden could be just used as printer. Thanks, Mike
My first problem is that the Friden Code does not have many of the ASCII codes, but I think I can get around that. For example there is no ESCAPE code or exclamation point. The exclamation point can be printed, using an Apostrophe, backspace, period. The Friden code contains many punch tape/card control characters some of which are actual keys on the key board. I think I can just convert some of these keys in the PI code conversion.
The second problem is whenever a key is pressed, the Friden code is sent to the PI AND the typing machine will independently print that character. If I connect this circuit to the RS232 comm port of my DEC PDP8E, a key press, the Friden will print the character and the PDP8E will send back that character. The key pressed character will be typed twice.. I'm a little confused on how the Friden could be used as a terminal with any computer that has a full duplex comm port, as the PDP8E. There is no way to stop the Friden from typing a character when a key is pressed. Is there a way to convert the comm port or operating system to half duplex? If that can not be done, I suppose the Friden could be just used as printer. Thanks, Mike