I have a Panasonic "Penwriter" model RK-P400C electronic typewriter/plotter from circa 1985 I'd like to be able to connect to a modern PC. And hopefully even use to draw graphics! Bought in almost new condition from eBay in its original packaging, it looked basically unused, with all the original pens. Which still work fine after probably 30 years sitting in a box.

I don't think this was ever a big seller in the United States where I'm located, the pen-plotter gimmick may have been originally designed as a way to draw higher-quality Japanese characters prior to injket/laser printers being commonly available to consumers. I can find limited information about it online except some mediocre reviews in a couple archived PC mags from the mid 1980s and a brief mention in the "Rainbow" Tandy CoCo newsletter from around the same time. I'm having difficulty even finding a PDF format scan of the owner's manual.

It has an RS-232 interface on the side on a female DB-25 connector so it can be connected to a PC or computer of some kind, but I haven't had any success getting it to print characters from Linux (Xubuntu 17.10), via either the "screen" command and attempting to directly connect to it at 300 baud over an FTDI chip-based USB to serial cable, or configuring it as a generic "IBM compatible" serial printer in the printer setup utility.

I've heard from a knowledgeable source that it likely uses a variant of the ALPS/Tandy plotter engine CGP-115 also used in the Atari 1020 pen plotter from around the same time, but that's all the intel they had on it.

It has a switch labeled "KBI, KBII, EXT" and when "EXT" is selected the display says "OFF LINE." pressing the key below labeled "ON LINE" changes the display to "ON LINE." I've made all the attempts at communication in that mode as intuitively that seems like what you'd want but there's no response.

Here's an ad for the Penwriter from Spin magazine, December of 1985. Wow.

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Update 10/9/18:

I was able to get my hands on a manual, however the only one I could find for a reasonable price was for a similar model, the RK-P200C. After some more head scratching and looking at a few pictures of the different models I think I understand the situation. It seems the RK-P200C was the budget model, it came with a 9 pin serial interface port on the side:


They made an expansion box, the RP-K100 that allowed you to connect a PC with a Centronics/parallel port and provided a serial output, and also I guess provided a memory buffer so you didn't lose your print job if the PC went down:


The model I have is the RK-P400C, the "flagship" model (or perhaps just a later variant.) This one has some of the same controls as the interface box "On Line", etc. integrated into its keyboard and so I'm guessing it's like the RK-P200C but with the RP-K100 features built-in, perhaps. And that the 25 pin connector may just be a regular PC printer/parallel port, not RS-232 on a 25 pin connector as I thought originally, which could certainly explain why it's not responding that way. It's not labeled on the typewriter in any way and has no "sheet of paper" glyph which may have become common later, so what it was was just a guess and I may have guessed wrong.

Edit 2: I may have been right the first time, I somehow managed to bring up a serial parameters display by mashing keys in "Online" mode. :) The default baud rate is 600 bps, data 8 bit no parity


  • 2
    300 baud sounds much too slow for a printer. I would guess the default speed would be 9600. Try all the speeds you can, all the combinations of start and stop bits, and all the handshaking options (RTS/CTS, AK/NAK, etc).
    – alephzero
    Sep 30, 2018 at 8:28
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    Not realy an answer, but AFAIR it was running at 2400 bd 8n1. ALso, there is a menue option on the typewriter to check/set the serial seting. These printers in general, and typewriter applications from Panasonic and Brother especial where quite popular around 1985. Ther wheree smaler ones by ALPS for Commodore, Tandy and otehres.
    – Raffzahn
    Sep 30, 2018 at 10:04
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    It only printed 6.5 characters per second, so low baud rates would be more than ample. Also there were apprently six pages of commands in the manual, which sounds like what you need to find (there's one on ebay). Gleaned from a review at americanradiohistory.com/Archive-Hands-On-Electronics/… Sep 30, 2018 at 19:05
  • 3
    I'm skeptical that it's a 25-pin parallel port because that would be uncommon. I think the first step is to get it to show "online" with the switch set to "ext". I think it says offline because it's waiting for DTR? Oct 10, 2018 at 1:51
  • 2
    Related (and a possible starting point): retrocomputing.stackexchange.com/questions/7371/…
    – tofro
    Oct 10, 2018 at 12:03

1 Answer 1


I successfully got the RK-P400C printing from a serial console (minicom on Linux) today. Here's how to do it for future reference...;)

The DB25 connector on the right side is a 25 pin serial port. At the top right of the typewriter there are sets of switches to select font and size, at the far right of those are two switches with the labels "KBI, KBII, EXT" and "DP, LL, COMMAND". For printing from the serial port set the first to "EXT" and the second to "DP" (direct print) mode.

When the switch is flipped to "EXT" the display will show "OFF LINE." On this screen by pressing return on the typewriter keyboard it will show the baud rate, parity, and line feed settings. Pressing space when a given setting is on the screen will adjust it. The possible baud rates are 110, 150, 300, 600, 1200, and 2400, with the choice of either 8 bit no parity or 7 bit even parity. A USB to 25 pin serial port adapter with an FTDI chipset works fine for me, but it seems to require a crossover-type cable or null modem adapter cable. No hardware flow control or software flow control enabled. Toggle the blue "ON LINE" key at the bottom right of the typewriter keyboard and it's ready to receive commands/ASCII characters.

That's it for now, I haven't had a chance to experiment with the graphics commands yet but this should print plaintext OK.

  • 3
    crossover/null modem makes sense - computer & most printer-like devices are both normally DTE. Oct 11, 2018 at 3:42
  • 1
    If you somehow can, also try to input information about the graphics commands online somewhere - if it's something well-known like HPGL, the fact that it uses a HPGL variant is probably enough, otherwise a list of commands would be nice. I tried googling for it when I saw this question, and essentially came up empty, so this would be good for anyone else who has one and wants to play around with it.
    – dirkt
    Oct 11, 2018 at 5:29
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    @dirkt I'm going to upload scans of the commands table from the RK-P200C manual soon as I get a chance, and then perhaps the rest of the manual. It's a very intricate piece of kit (in the Japanese style) with many special functions and complex menus/code commands without the manual pretty much hopeless to figure out
    – MattyZ
    Oct 15, 2018 at 17:17
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    As far as I can tell the RK-P200C and P400C are more-or-less identical except the 400C has a different serial interface connector and some of the features of the optional interface box built in, plus there are more switches for easy access to font/character size settings at the top right as compared to having to change them via the LCD menu interface. my guess is the 200C was more or less a direct port of a domestic Japanese product except for language changes/localization while the 400C was altered a bit for foreign or US market
    – MattyZ
    Oct 15, 2018 at 17:22
  • @bitrex did you manage to scan this?
    – chx
    Jun 7, 2019 at 8:57

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