Hi all. I'm contemplating keyboard options for my build. Currently Using serial connection to laptop for input. I've recently finished my homebrew VGA text controller, so video is in the bag (all 7400 logic. Details coming if interested)

My current plan is a PS/2 style keyboard interface. Its readily available, and I could do all the decoding in hardware, which is my preference. Can't really think of a con to this plan, except I guess it isn't period accurate. Period accuracy is a plus to me, but not a deal breaker.

Are there other options? I know you can get laptop keyboards easily, but I can't find any info on the interface.

Are there options I don't know about? USB is out, even with a serial interface. Too modern for my sensibilites.

Daryl (8BIT) offers a couple of solutions:
http://sbc.rictor.org/pckbavr.html
http://sbc.rictor.org/pckb6522.html

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

There's also the RC2014 Universal Micro Keyboard, which can interface over serial, USB(with a caveat), or as a raw key matrix(you need to scan this yourself). Its layout is QWERTY-based, but definitely not standard.
I use the serial option, and the ATMega on board can be re-programmed to change the key map, if you so desire(the firmware is open-source).
The main reason I mention it is that kits are available (https://www.tindie.com/stores/Semachthemonkey/).

You can buy keys and keycaps on aliexpress (search for MX keys) in many different varieties, including blank ones. I have a set at home that I'm planning to use for a project.

Which period though

Apple I and Apple II used a commercial keyboard that presented 7-bits + strobe... Before that, the 8-bit stuff was mainly serial terminals and after that, it was a few years before the micro makers started to do their own key matrix scanning by the cpu rather than use an off-the-shelf keyboard decoder chip (mainly to get the prices down AIUI).

I think using a PC ps/2 type keyboard with an ATmega (or PIC) presenting a 7/8-bit port + strobe out (and ack back) is a good compromise though - so you could treat the keyboard + microcontroller as the keyboard in total, so your micro still sees an older parallel interface and doesn't have to worry about the scanning, decoding, etc.

There are microcontrollers (e.g. ATmega 32u4) that have USB interfaces, so could use a usb keyboard and still present the same 8-bit interface back to the micro though - again treating it as a black-box keyboard so your micro only sees the parallel interface.

Actually - hm. an interesting project, maybe, although I'm sure it's already been done - ah yes: http://sbc.rictor.org/pckbavr.html and if you have a big old ps/2 keyboard you might even be able to squeeze that inside the keyboard case somewhere with nothing more than a ribbon cable coming out.

Cheers,

-Gordon

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Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

One guy at the retrobrewcomputers forum has a design for a keyboard for an MSX2-style computer: https://www.retrobrewcomputers.org/forum/index.php?t=msg&th=252&goto=5838&#msg_5838. This might be a good option for other designs, too.

Or use a 2nd 6502 processor.

There's a small subculture of folks building their own keyboards from the boards up.

There's board designs, firmware for microcontrollers, sources for cap and buttons.

I don't know why you can't take $20 keyboard, open it up, cut the traces to the on board controllers, and then wire it up to your project.

They're all matrix keyboards, they all poll their keys, not a lot of new work being done here.

You could use a 6502 to make a keyboard controller. You could use the W65C134S to reduce chip count, since it has a bunch of ports and such. You'd need a *ROM of some kind for the firmware, but 192 bytes of onboard RAM should be enough.

You can bit bang the keyboard protocol for AT keyboards, or do your own thing.

Point being there's opportunity to start at as high or low level as you like.

A serial interface with a standard connector would be interesting, giving you the option of removing keyboard and using a PC with terminal program instead.

Yes please.

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Cat; the other white meat.

The adaptor that comes with PS/2 compatible USB keyboards contains no electronics. Its just passes through the signals and power.

Several USB keyboards test for USB protocol on startup and if they don't find it revert to PS/2 mode.

On one of my boards I used a USB socket rather than a PS/2 DIN to save board space.

Just a thought.

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Andrew Jacobs
6502 & PIC Stuff - http://www.obelisk.me.uk/
Cross-Platform 6502/65C02/65816 Macro Assembler - http://www.obelisk.me.uk/dev65/
Open Source Projects - https://github.com/andrew-jacobs