IBM 5121 Conversion

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snacksthecat
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IBM 5121 Conversion

Unread post by snacksthecat » 28 Dec 2018, 04:49

I have the next few days off so I'm going to get a start on trying to convert my IBM 5121 keyboard. I haven't done any research yet, but it seems like people almost always put an xwhatsit or commonsense controller in these. I might eventually go that route but I'd like to mess around with it a bit first.

Here are some photos of the keyboard.

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John Doe

Unread post by John Doe » 29 Dec 2018, 07:55

Nice find, continue the conversion progress with more photos, please.

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snacksthecat
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Unread post by snacksthecat » 31 Dec 2018, 21:28

I've got everything wired up based on the connector pinout found on kbdbabel

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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.

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Thanks!

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snacksthecat
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Re: IBM 5121 Conversion

Unread post by snacksthecat » 11 Jan 2019, 01:48

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.

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Muirium
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Re: IBM 5121 Conversion

Unread post by Muirium » 11 Jan 2019, 04:30

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!

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pansku
Member of the Beam Spring cult

Re: IBM 5121 Conversion

Unread post by pansku » 11 Jan 2019, 15:07

Personally I wouldn't try reinventing the wheel. There is a converter using the original controller already.

https://github.com/MMcM/ibm-5251-kbd

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