My first wire wrap: Wilf's AT keyboard interface

Discussions about Sinclair ZX80 and ZX81 Hardware
User avatar
mrtinb
Posts: 1906
Joined: Fri Nov 06, 2015 5:44 pm
Location: Denmark
Contact:

My first wire wrap: Wilf's AT keyboard interface

Post 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.

Image

Image
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
User avatar
1024MAK
Posts: 5102
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: My first wire wrap: Wilf's AT keyboard interface

Post 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 :mrgreen:

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
User avatar
mrtinb
Posts: 1906
Joined: Fri Nov 06, 2015 5:44 pm
Location: Denmark
Contact:

Re: My first wire wrap: Wilf's AT keyboard interface

Post by mrtinb »

You can just cut the bottom wire if there's room above
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
User avatar
mrtinb
Posts: 1906
Joined: Fri Nov 06, 2015 5:44 pm
Location: Denmark
Contact:

Re: My first wire wrap: Wilf's AT keyboard interface

Post by mrtinb »

I've redesigned the board after I got hold of a wire wrap version of the edge connector. There's still a lot to wire. :)

Image

Image
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
User avatar
gammaray
Posts: 590
Joined: Sun Apr 17, 2016 2:44 am
Location: Texas

Re: My first wire wrap: Wilf's AT keyboard interface

Post 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/
5-TS1000,UK ZX81<-Sheelagh, US ZX81, 2-TS1500/KDLX , 3-TS2040 printer, 2-TS2020 cassette decks, ZXPAND+AY, ZeddyNET, ZXBlast, UDG, ZX8CCB, AERCO, BUILDS/REPAIRS ZX Spectrum, ZX80 Minstrel, ZXMAX48 v1 v2, 2-TS-2068, ROM, 16kRAM
User avatar
mrtinb
Posts: 1906
Joined: Fri Nov 06, 2015 5:44 pm
Location: Denmark
Contact:

Re: My first wire wrap: Wilf's AT keyboard interface

Post 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.
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
User avatar
mrtinb
Posts: 1906
Joined: Fri Nov 06, 2015 5:44 pm
Location: Denmark
Contact:

Re: My first wire wrap: Wilf's AT keyboard interface

Post 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.
Image
Image
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
User avatar
mrtinb
Posts: 1906
Joined: Fri Nov 06, 2015 5:44 pm
Location: Denmark
Contact:

Re: My first wire wrap: Wilf's AT keyboard interface

Post 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?
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
User avatar
PokeMon
Posts: 2264
Joined: Sat Sep 17, 2011 6:48 pm

Re: My first wire wrap: Wilf's AT keyboard interface

Post 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.
User avatar
mrtinb
Posts: 1906
Joined: Fri Nov 06, 2015 5:44 pm
Location: Denmark
Contact:

Re: My first wire wrap: Wilf's AT keyboard interface

Post 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?
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
Post Reply