Thanks. I'll give that a good read.1024MAK wrote: ↑Thu Mar 14, 2024 3:31 pm I can point you to the schematic for my Kempston compatible joystick interface. It's in [url=viewtopic.php?f=7&t=3242]this
Atari joystick without ZXpand+
Re: Atari joystick without ZXpand+
All that I've learned - https://msknight.com/bbc/index.html#zx81
- 1024MAK
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Re: Atari joystick without ZXpand+
Still active, has visited this week.
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor 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 being good this year.
ZX81 Chip Pin-outs
ZX81 Video Transistor 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 being good this year.
Re: Atari joystick without ZXpand+
I was looking at the schematic and wondering how external keyboards work via the edge connector if there is no access to the five KBD lines that go to the ULA. Is the ROM checking for keypresses? I haven't yet tripped over how this actually works yet.
All that I've learned - https://msknight.com/bbc/index.html#zx81
- 1024MAK
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- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: Atari joystick without ZXpand+
As far as I am aware, all the later Kempston versions did have the longer ZX Spectrum edge-connector sockets.
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor 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 being good this year.
ZX81 Chip Pin-outs
ZX81 Video Transistor 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 being good this year.
- 1024MAK
- Posts: 5302
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: Atari joystick without ZXpand+
That's an entirely new subject...
The simple answer is that for an external keyboard connected to the expansion port/edge-connector, you need a bunch of circuitry that duplicates some of what the ULA does. Hence if you look at the Memotech Keyboard, it has a Keyboard Interface...
Because the ULA has outputs similar to "open collector data bus output drivers", other I/O devices can override its outputs. Hence an external interface can detect when the Z80 (machine code) tries to read the keyboard, then it outputs its data overriding the ULA. The Z80 and hence the code then sees the key pressed on the external keyboard
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor 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 being good this year.
ZX81 Chip Pin-outs
ZX81 Video Transistor 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 being good this year.
Re: Atari joystick without ZXpand+
I've been doing something very dangerous... thinking.
Games use keyboard presses. External keyboards, "barge in," to the conversation that's going on.
So why, when the ZXpand+ is programmed with keypresses for joystick maps... do some games need to be re-written?
I believe... and this is very dangerous for me... that the ZXpand+ is putting the keypress in a buffer and is not actually barging in to the ULA-Z80 conversation.
So other joystick solutions that do barge in to the conversation, wouldn't need the games to be re-written?
Games use keyboard presses. External keyboards, "barge in," to the conversation that's going on.
So why, when the ZXpand+ is programmed with keypresses for joystick maps... do some games need to be re-written?
I believe... and this is very dangerous for me... that the ZXpand+ is putting the keypress in a buffer and is not actually barging in to the ULA-Z80 conversation.
So other joystick solutions that do barge in to the conversation, wouldn't need the games to be re-written?
All that I've learned - https://msknight.com/bbc/index.html#zx81
Re: Atari joystick without ZXpand+
As long as games use the inkey equivalent they don't need to be rewritten. That's what zxpand offers to the zeddy or otherwise it's own API.
Joy81 on the other hand implemented the exact keyboard behaviour and so games need not be rewritten.
Joy81 on the other hand implemented the exact keyboard behaviour and so games need not be rewritten.
In theory, there is no difference between theory and practice. But, in practice, there is.
Re: Atari joystick without ZXpand+
Joy81 is no miracle and we can make new boards if you're interested (or others as well)
It also offers multiple key presses and diagonal keys not only up and down.
It also offers multiple key presses and diagonal keys not only up and down.
In theory, there is no difference between theory and practice. But, in practice, there is.