Running teletype with an apple ii plus

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Thatguyagain's picture
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Running teletype with an apple ii plus

So i have a unusual project.  I have a model 15 teletype and i would like to try and make it behave with my apple ii plus though an interface board and a rs-232 to 25 pin null cable.  Im using an apple super serial two card set to 300 baud and terminal mode.  I could use some words of wisdom or ideas.  Is there a program made i could try to find or dip switch settings i could try?  Any test ideas to verify my super serial 2 card is even working (total unknown i located it just for this project).  I have located and consulted the manual for the card and think im close.

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Baudot, not ASCII

The Teletype Model 15 was introduced in 1930, 30 years before the ASCII character set existed. It uses 5-bit "Baudot" characters.

It may be possible to program the SSC for 5-bit words, but changes to software to support 5-level character sets are also needed.

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bps

The unit also operates at 45.5 bps, which may be a challenge for any serial card using a modern UART.

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One solution would be to plug

One solution would be to plug an Arduino on the interface board you mentioned, which could convert the 45.5 bps 5bit Baudot data to an ASCII RS232 stream - which you connect to the SSC. This allows you to use any Apple II terminal programs to display the data.

Alternatively, 45.5bps is slow enough to allow the 6502 to decode the data manually. You would only need a one bit interface at the Apple II. You could even use the Apple II audio-in jack to read the data. Then write some 6502 code to read the audio input, measure the bit timing, decode the 5bit Baudot to ASCII - and display it on the screen.

In any case, you will need some interface to convert the 120V current loop signal of the teletype to some acceptable voltage level. You cannot connect it to the audio-in jack directly (nor to the SSC).

Did you watch CuriousMarc's video on using a 1930's teletype as a Linux terminal? He made a little interface with proper galvanic isolation to connect the teletype's signal - and then also used an Arduino to convert the baudot to ASCII/RS232.

 

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