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IBM 5121 Conversion
Posted: 28 Dec 2018, 04:49
by snacksthecat
Posted: 29 Dec 2018, 07:55
by John Doe
Nice find, continue the conversion progress with more photos, please.
Posted: 31 Dec 2018, 21:28
by snacksthecat
I've got everything wired up based on the connector pinout found on kbdbabel
However, according to this I need to supply -5v to one of the pins. I'm not sure how to do that. Does anyone here know how I could power this keyboard?
I need to supply 5v, -5v, and 8.5v (I have a 9v step up regulator). I'm not opposed to purchasing something.
Thanks!
Re: IBM 5121 Conversion
Posted: 11 Jan 2019, 01:48
by snacksthecat
Bump
I don't understand electricity. Can any of the bright minds of DT help me learn? I need to power this keyboard with 5v, -5v, and 8.5v.
Re: IBM 5121 Conversion
Posted: 11 Jan 2019, 04:30
by Muirium
GND == 0 volts. Everything else is based off that. Put a 5v source's negative end on GND and positive end on +5 and you've got yourself +5v; swap it round and you've got -5v. GND is the common.
The pinout does kind of invite powering it up and watching those Scan Bit lines. Note how there's 7 of them: reminds me of
ASCII. Keyboard protocols are usually a bit more complex than that, however. I mean, if you did power it up, poked keys, and it spat out ASCII codes, it'd be 1KRO!
(And don't forget IBM had an iffy relationship with ASCII, what with
EBCDIC. Hopefully that all pre-dated this board and its mysterious protocol.)
Ultimately, you're turning towards CommonSense, I'm sure! But there's no obvious harm to be done playing with IBM's original controller first, I suppose. Just don't go frying batteries or power supplies with short circuits!
Re: IBM 5121 Conversion
Posted: 11 Jan 2019, 15:07
by pansku
Personally I wouldn't try reinventing the wheel. There is a converter using the original controller already.
https://github.com/MMcM/ibm-5251-kbd