Canon Typestar 10-II electronic typewriter main board. CPU is a Renesas 3806-family, directly controlling keyboard matrix, LCD display, paper feeding and indirectly controlling printing head. i wanted to make it into a serial printer by emulating the keyboard matrix but no luck
turns out emulating a matrix keyboard is a bit more involved than just pulling a wire high or low, and would require quite a few ancillary ICs than just a microcontroller. unfortunately i see no other point of attack to automate keypresses on this rn, defeating my plan for now
the typewriter itself is neat but clearly a very cost-cut model about a decade into the typestar line. earlier models had options such as serial and typeface cartridges, which this lacks. it can print on regular paper, provided you have the rare thermal tape, or any thermal paper
however, this presents an interesting hack: those ink tape cartridges are not supposed to be reusable, but since so much ink is left on them, if you're careful enough you can take it apart and re-spool the tape anew. the print will be far from perfect, but it works
by the way before someone corrects me yeah i know it's not exactly ink that's on those tapes, it's more like a layer of toner adhered to a plastic film tape, which then melts with the printing head, forming letters on the paper. i'm just using "ink" to work around character limit
oh: the ROM chip you see on the top side of the board in the OP: that's labelled as the "DICT. ROM" which i assume is just for the spellchecker dictionary. IIRC is writable since you can add words to the spellcheck, but that function isn't terribly interesting for me to dump it
i'm really quite frustrated i couldn't go through with my plan to turn this into a serial printer to play with printing out ASCII art onto thermal fax paper, so my brain is just shutting down about it. hopefully i can just put this back together and enjoy it as a typewriter
if you have ideas on how else i could approach this other than several 4066 chips, please let me know
bonus: since i put it back together, here's the Typestar 10-II in action. although the ink cartridges are no longer made, it works fine with readily-available fax paper rolls
incidentally, these types of thermal ink tape typewriters are infamous for being notorious security liabilities. the way they print on regular paper is thru melting off ink similar to toner onto paper, leaving a very clear negative of whatever you wrote onto the disposable tape