How I convinced my 1987 Canon Cat to talk to my 2017 MacBook Pro

Marcin Wichary
2 min readNov 21, 2017


Canon Cat is a wonderful machine that means a lot me. I recently managed to get it to talk to my modern MacBook Pro. It took some time to figure it out, so I thought I’d share. It might also be useful info for connecting other older computers to newer ones via a serial port.

My Cat has a broken floppy drive — which is a common affliction — and my first attempts to connect it using a USB modem and phone cable failed. Here’s how to do the right way:


Setup on a Mac

Setup on the Cat

  • Press [Use Front]+[Setup] a few times to go to Serial Port Connection.
  • Make sure it says Connect to: SEND Command (and not alternate printer).
  • Switch Communications mode to Full Duplex.
  • Switch Line terminator to CR/LF.
  • Leave other options as 9600/8 bits/no parity/1 stop bit.

Starting a conversation

  • Connect the USB to my computer, and the other side to the Cat through the adapter.
  • Power up both machines.
  • On the Mac, open Terminal and type cat /dev/tty.Repleo-PL2303-00006114. Note that the last digits might be different, usually you can just type all the way to Repleo and press [Tab] to autocomplete.
  • Press [Ctrl]+[C] to abort. I am not sure why these last two steps are necessary, but without them the communication only works one way.
  • Type screen -L /dev/tty.Repleo-PL2303-00006114.

You’re done!!!

  • What you type on your MacBook will appear on Cat’s screen immediately. To send more stuff, just copy and paste into the Terminal window.
  • You can select text using leaping, and press [Use Front]+[Send] to send it back to the Mac.
  • The -L option makes sure that the output is saved in a screenlog.0 file.

This experiment was made as part of writing a book about keyboards.