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isochronic
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Joined: 21/01/2012
Location: Australia
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Posted: 11:21am 16 Apr 2018

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I rescued an old daisywheel typewriter a while ago. It works, very noisily !
The intent was...yada ...yada ... anyway... it looks like it had an
interface added so as to enable use as a printer. I very vaguely
remember there were popular articles written about that, I thought one
was in ETI but I can't see it. The interface has a 25 pin connector,
maybe Centronics parallel ?(!) Anyone remember these things ?

VK2MCT
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Joined: 30/03/2012
Location: Australia
Posts: 120

Posted: 11:41am 16 Apr 2018

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Daisywheel or Golfball ?
IBM Golfball and interface I know about.

JohnEdited by VK2MCT 2018-04-17

matherp
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Joined: 11/12/2012
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Posted: 12:53pm 16 Apr 2018

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Quote I very vaguely remember there were popular articles written about that

Can't help with the daisywheel but many years ago (April 1978) I had an article in issue 3 of Personal Computer World showing how to connect a teletype to a Commodore PET (110 baud, 20mA current loop) and providing 6502 machine code to allow you to print program listings and output from within a program - happy days

redrok

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Joined: 15/09/2014
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Posted: 12:54pm 16 Apr 2018

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Hi chronic;

chronic said I rescued an old daisywheel typewriter a while ago. It works, very noisily !
The intent was...yada ...yada ... anyway... it looks like it had an
interface added so as to enable use as a printer. I very vaguely
remember there were popular articles written about that, I thought one
was in ETI but I can't see it. The interface has a 25 pin connector,
maybe Centronics parallel ?(!) Anyone remember these things ?

I suspect it's a conventional RS-232 serial interface. That means the serial voltages are up to +- 12V or so.

To be fair there were 25pin Centronics parallel interface connector variants. Notably on the original IBM PC. But I don't think that is what you have, kind of rare.

I used to have a Brother Daisy wheel which has the standard 25 pin serial interface. It used standard ASCII protocol, and not the IBM EBDIC serial.

Kind of slow, but did very high quality printing.

redrok

Phil23
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Joined: 27/03/2016
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Posted: 10:38pm 16 Apr 2018

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I'd take a stab at it being serial as well.

Is the interface a 25 Pin D connector?

If so, look at the voltages on Pins 2 & 3 with respect to ground, (Pin 7).

Depending on which pin has the -12V? (or is it +12 idle), Pin 2 or 3 will indicate if it's a DTE or DCE calss device. Basically the two transmit & receive on opposite pins.

Cheers

Phil

CaptainBoing

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Joined: 07/09/2016
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Posted: 07:26am 17 Apr 2018

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Phil23 said
Depending on which pin has the -12V

You are right. "proper" RS232 Marks with -12V and is left in a marking state when idle. I am sure there are variations but I never met one.

I used to use this to steal a negative supply with a diode/capacitor pump on stuff connected to RS232 with no negative supply available

Edited by CaptainBoing 2018-04-18

isochronic
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Joined: 21/01/2012
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Posted: 12:40pm 17 Apr 2018

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Thank you all ! At this stage it looks most like the full rs232,
so I'll check that direction. It's a long time since I saw full RTS/CTS etc.
It was a third-party conversion so it is a bit unusual.
There is a sticker with the original service address on it - but that address has been beneath a shopping mall for decades.
Quite impressive engineering with a daisywheel and hammer etc all precisely located on a snap-to-grid using steel wire and steppers.
Originally I was thinking of using the 0.1 inch spacing for component layout on a pcb somehow, not much point now, considering the 3d printers available.

Quazee137

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Joined: 07/08/2016
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Posted: 01:36pm 17 Apr 2018

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easy check if pin 25 to I think 18 is all ground it the old IBM port interface.

Phil23
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Posts: 1667

Posted: 10:52am 19 Apr 2018

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chronic said Thank you all ! At this stage it looks most like the full rs232,
so I'll check that direction. It's a long time since I saw full RTS/CTS etc.

So now the fun begins!

Out with the break box with the LEDs, DIP switches & jumpers, try & work out how the Hell DTR/DSR & CTS/RTS need to be wired on this occasion...

Xon/Xoff.... Might be luck & be able to use that in a very few cases...

Phil.

Quazee137

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Posted: 02:54am 21 Apr 2018

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@chronic

here is a free windows tool to debug/test serial driven devices.
ComDebug

and a site with quick run down on usage of signals
Serial ref

Years ago I built a Z80 based IBM Selectric golf ball typewriter to printer
board. It had both serial and Diablo interfaces. Had 4k byte buffer expandable
to 128k with bank switching dram. The driver for CP/M was really a bios hook.
Sadly the design is in TANGO sch/pcb and all code is asm, and on 8" floppy.

Hope the test software can help see the needed pin functions.

QuazeeEdited by Quazee137 2018-04-22

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