Johan_Ha:
Well, the Canon typewriter has an LCD. Probably for typing and editing one line at a time before printing. But I've already done some harm to the original electronics, so I guess I've destroyed my chances to actually take over the character handling logics. The typewriter seems to be from 1987 and I don't think I'm going to hack into the LCD. But I could still use the keyboard for something.
Oh, that sucks.
All the printer i've seen with LCD can be put into "direct" mode where it's printing right away, so that could have worked.
Anyhow, since you broke the electronics, you will have to sort out your own. I tried doing that but stopped the project since the old steppers found ind typrwriters are high-voltage (30-45V), high-inductance motors, not suited for "modern" hybrid-stepper-drivers unfortunately.
If the darlington-drivers on the PCB are still ok, i would just remove the CPU and drive the darlington-drivers directly from the Arduino.
// Per.