Author Topic: Interface Keyboard to TRS-80 Model II  (Read 1473 times)

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Offline rthornquTopic starter

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Interface Keyboard to TRS-80 Model II
« on: November 24, 2017, 04:24:46 pm »
I just acquired a TRS-80 Model II in great condition.  One problem: It didn't come with a keyboard.

I'm searching for a keyboard, but the Model II wasn't that popular and I think it'll be tough to find one.  In the meantime, I was considering a way to interface a regular PC keyboard to the Model II.  I have some documentation for the Model II keyboard pinouts, codes, and timing - please see attached.

One idea was to use a Raspberry Pi.  The Pi already has a keyboard attached to it so all I'd have to do is attach a few GPIO pins to the keyboard connector on the Model II and generate the required signals.  However, I'm not sure the Pi has the ability to generate signals with such precision.

If anyone has any ideas on how would be a good way to do this, please let me know.  Thanks!

- Rick Thornquist
 

Online Ian.M

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Re: Interface Keyboard to TRS-80 Model II
« Reply #1 on: November 24, 2017, 04:58:02 pm »
There is no way that you can reliably meet 1us scale timing requirements on a Pi (or on anything else running Linux or other high level OS) without hardware assistance.   

The easy option would be an Arduino or other 8 bit MCU with similar capabilities.  The keyboard data and clock look similar to SPI but bit-reversed, and with an extra end pulse that would need to be bitbanged after each byte.   There are existing Arduino libraries for PS/2 keyboards.   Prototype it on an Arduino UNO then open up the keyboad and convert it to TRS-80 by shoe-horning in an Arduino Mini.
 

Offline rthornquTopic starter

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Re: Interface Keyboard to TRS-80 Model II
« Reply #2 on: November 24, 2017, 08:25:47 pm »
Ian -

I took a look at the Arduino and the PS/2 keyboard libraries and it looks like it should work nicely.  Thanks for your help!

- Rick Thornquist
 


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