[Coco] Mechanical keyboard upgrades for the CoCo

Zippster zippster278 at gmail.com
Tue Aug 25 22:17:18 EDT 2015


Well, really the behavior could be pretty much whatever you want, especially if you take each switch in
on it’s own IO pin.  There’s more you can work with in a CPLD than strictly a bunch of logic gates.

But absolutely agree that everybody should build what they want to.  There’s not much reason to do it otherwise.

- Ed


> On Aug 25, 2015, at 7:59 PM, Mark J. Blair <nf6x at nf6x.net> wrote:
> 
> 
>> On Aug 25, 2015, at 15:59 , Brian Blake <random.rodder at gmail.com> wrote:
>> 
>> And all of the above is why it makes sense to just use off the shelf key
>> caps and use a CPLD to remap those keys that need to be done - that removes
>> the cost of custom key caps.
> 
> 
> I don't like the CPLD approach. I would expect weird things to happen. For example, if one was to perform the following sequence:
> 
> 1) Press and hold the 2 key.
> 2) Press a shift key.
> 3) Release a shift key.
> 4) Release the 2 key.
> 
> On a regular CoCo keyboard, that's the exact sequence that would be seen by any keyboard polling routine. But with a PC layout being translated to the CoCo matrix, the sequence would necessarily look like this (with implementation-specific make/break ordering) as seen by the CoCo:
> 
> 1) 2 key pressed
> 2) 2 key released, shift key pressed, @ key pressed
> 3) @ key released, shift key released, 2 key pressed
> 4) 2 key released
> 
> This might not cause any actual problems with existing software, but it's just not the thing that I want to make. I want a passive matrix, electrically identical to original CoCo keyboards, and using a layout very close to one of the original ones. Just constructed with better keyswitches. Basically, a new implementation of the old HJL-57 keyboard upgrades, since I can't order up a new HJL-57 from an ad in Rainbow Magazine any more.
> 
> I may or may not actually build the keyboard that I have in mind, but I certainly won't build a CPLD-based keyboard with PC-style mapping, nor will I build any sort of external keyboard interface (which exists as a product from Cloud 9 anyway, for anybody who wants one). If somebody else would like to build a CPLD-based keyboard, USB keyboard adapter, etc., then I think that's just great! There's plenty of room for folks to build all sorts of cool projects to get exactly what excites them, and I think it's wonderful that the CoCo still has such an involved community after 35 years.
> 
> -- 
> Mark J. Blair, NF6X <nf6x at nf6x.net>
> http://www.nf6x.net/
> 



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