Date   : Thu, 16 Oct 2008 17:21:00 +0100
From   : jumbos.bazzar@... (Mark Haysman)
Subject: master keyboard

Hi Folks.

The BBC Micro keyboard was scanned with the VIA thru some discreet logic 
contained on the KB itself, but the KB in the master has no logic on it at 
all, and is scanned with one of the cutsom chips, and that data is then fed 
to the VIA. However, I still don't think that Custom IC provides an ASCII 
output, as there is a direct connection on the Master PCB for a BBC B 
keyboard direct to the same VIA, so the Custom may just simulate the logic 
on the Bs keyboard.

A microcontroller sounds like a good solution. PICs was something I've never 
got into, I alway use an 8x51 when I need something like that, as they're 
pretty quick at 24MHz and cheap at under a quid for an Atmel Flash version.

Mark.

----- Original Message ----- 
From: "Jules Richardson" <jules.richardson99@...>
To: "BBC micro mailing list" <bbc-micro@...>
Sent: Thursday, October 16, 2008 1:49 PM
Subject: Re: [BBC-Micro] master keyboard


> Rob wrote:
>> Sorry, no.
>>
>> It's a matrix which is scanned by the system VIA and decoded by the
>> OS.   There is no decoding to ASCII or otherwise done on the board.
>
> Yeah, I guess they changed as it was cheaper to do it that way; the 
> earlier
> System keyboard was ASCII. I had a heck of a job tracking one of those 
> down
> (or indeed any parallel ASCII keyboard as a substitute) when I needed one.
>
>> I used to have (might still have) an old viewdata terminal keyboard
>> that was RS232 ASCII based, but that's going back well over 20
>> years...
>
> That could work if fed through the appropriate gubbins. Although when 
> looking
> for parallel keyboards as above I considered doing this, but even finding 
> a
> serial ASCII setup was proving hard (I found a couple of such 1970s 
> terminal
> keyboards, but they were built like tanks and would have required a 
> complete
> rebuild to get rid of oxidisation problems)
>
> I believe the RML 380Z keyboards were parallel ASCII - but they're rare as
> hens teeth these days (380Z systems seem to be found keyboardless 90% of 
> the
> time). 'Sacrificing' one probably wouldn't be good classic computer karma.
>
> My feeling would be that if you're building a Z80 system from scratch then 
> you
> probably know enough about what you're doing to rustle up something that 
> can
> take the stock BBC keyboard and spit ASCII out at the far side via a 
> little
> PIC micro or similar (or just use the VIA approach and do the scanning in
> software as with the BBC) :-)
>
> cheers
>
> Jules
>
>
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