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My first wire wrap: Wilf's AT keyboard interface
Posted: Sun Dec 31, 2017 10:12 am
by mrtinb
Hi
I'm trying to create Wilf's AT keyboard interface
http://www.user.dccnet.com/wrigter/inde ... XATKEY.htm http://wilfr.000webhostapp.com/index_files/ZXATKEY.htm .
It's my first time trying a project with wire wrap. It's cool you can modify without soldering and reuse the parts in the final design. But I didn't expect the wire wrap sockets to be SO expensive. It's mostly because I can't buy them cheap in China but from local old storage with high prices.
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Sun Dec 31, 2017 7:50 pm
by 1024MAK
Yeah, there are lots of advantages to wire wrap. However, one painful thing is if you have to remove(unwrap) a wire on the "bottom" of a pin due to a mistake/error/change of mind after wrapping one or more other wires further along the pin...
And when properly constructed, a wire wrap board can have a service life of 30 or more years
Mark
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Sun Dec 31, 2017 7:56 pm
by mrtinb
You can just cut the bottom wire if there's room above
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Sat Jan 13, 2018 11:46 pm
by mrtinb
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Sun Jan 14, 2018 3:33 am
by gammaray
Exactly the reason to wirewrap, you can change your prototype!
Nice!
Were you able to find the program mentioned "keyb18xa.bas" or starting without?
Found this...
https://www.phanderson.com/picaxe/
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Sun Jan 14, 2018 10:14 am
by mrtinb
My plan is to replace it with an Arduino Pro Mini, but this first version will just have the DIP switches to see the concept working.
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Tue Jan 16, 2018 5:38 pm
by mrtinb
So now the wires have been wrapped and this is the first prototype with DIP switches in place of Arduino controller and keyboard.
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Tue Jan 16, 2018 5:48 pm
by mrtinb
Wilf's AT keyboard (
and backup copy here) uses only A0, A8 to A15. That means he reads these addresses:
11111110???????0
11111101???????0
11111011???????0
11110111???????0
11101111???????0
11011111???????0
10111111???????0
01111111???????0
That does not give I/O $FE, because all he ensures is that circuit answers to 0 in lowest bit. A1 to A7 is not connected.
Does his circuit not miss an address decoder so the circuit is only enabled on I/O $FE?
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Tue Jan 16, 2018 6:22 pm
by PokeMon
It is typical for the ZX81 that there is no full address decoding used and keyboard responds to all i/o addresses with D0=0.
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Tue Jan 16, 2018 6:27 pm
by mrtinb
But wouldn't this interface conflict with any other device with A0=0? Wouldn't it conflict with any device with even I/O address?
