Despite what the hipster who carries an old Smith Corona to the coffee shop will tell you, typewriters are not practical machines in our modern world. Even the most basic word processing software is superior in every conceivable way. In the ’80s, as personal computers became commonplace, typewriter manufacturers tried to stay relevant by adding new electronic features. The Brother AX-25, for example, has 9kb of internal storage and the ability to display stored text on a small 16-character LCD. YouTuber Artilllect has a Brother AX-25 typewriter and decided to convert it to a paper terminal that connects to a modern computer.
This project is similar to my own TI Silent 700 project, where I connected a vintage ’70s paper terminal to a Raspberry Pi. But Artilllect’s project has one big difference: his typewriter was never intended to interface with a computer to act as a terminal. The Brother AX-25 was just a nice (for the time) electric typewriter. Instead of mechanical linkages, the keyboard sends electronic signals to the daisy wheel print head. Other than that and the internal memory, it works like a normal keyboard. But that electronic keyboard turned out to be the key to Artilect’s ability to interface with this typewriter.
Like a standard computer keyboard, the Brother AX-25 uses a keyboard matrix. It may be possible to read key presses by monitoring the rows and columns of the matrix. It also makes it possible to simulate key presses, which is exactly what Artilllect does. He connected and Arduino Uno development board to row’ and columns’ pins through multiplexers. By setting the appropriate pins HIGH or LOW, Artilect can use the Arduino to trick the typewriter into thinking it has received a key press. It will then type the corresponding character, just as if a user had actually pressed a key.
Artillect can control what is typed on the typewriter, but something needs to be done with that ability. So he connected the Arduino to a Raspberry Pi 4 Model B single-board computer with UART serial output. Anything that the Raspberry Pi can output through the serial port, such as terminal prompts and commands, is sent to the Arduino, which then converts the text into simulated key presses printed by the typewriter onto paper.
The last step in the puzzle is to provide input to the terminal running on the Raspberry Pi. I’m not sure why Artilllect doesn’t just read the input from the typewriter keyboard, but for some reason it’s not an option. Instead, he connected his laptop to the Raspberry Pi to type commands. The typewriter still prints those commands, so the paper roll has a fully printed terminal log.
The result is a recreation of paper terminals made by TI and others in the ’70s. Artilllect even print ASCII art!