How to Build a keystick port internally to zx81

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RS232
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How to Build a keystick port internally to zx81

Post by RS232 » Fri Apr 12, 2019 9:04 am

Was just thinking about squeezing a joystick pork inside a zx81. Taping the 5 6 7 8 and 0 keys should be possible with some careful soldering to the keyboard membrane sockets on the board. Tried it yet anyone?
I thing the tophalf of the membrane leads to one socket the bottom half to the other..

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siggi
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Re: How to Build a keystick port internally to zx81

Post by siggi » Fri Apr 12, 2019 10:28 am

Connecting a joystick directly to the keyboard lines will overload the Z80 addressbus (driving the keyboard lines), because the capacitive load of the long cable to the external joystick is too high.
At least some additional components (transistors or driver ICs) are necessary to drive this long cable.

HTH Siggi
My ZX81 web-server: online since 2007
http://zx81-siggi.endoftheinternet.org/index.html

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mrtinb
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Re: How to Build a keystick port internally to zx81

Post by mrtinb » Fri Apr 12, 2019 2:41 pm

Or you could get a JoyKey from the German forum.

This needs an external keyboard buffer like Wilf Rigter’s BKBv3 or German team’s keyboard pcb.

http://forum.tlienhard.com/phpBB3/viewt ... f=2&t=2776

http://www.user.dccnet.com/wrigter/inde ... XKBDv3.htm
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

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RS232
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Re: How to Build a keystick port internally to zx81

Post by RS232 » Sat Apr 13, 2019 1:23 pm

Thanks for feedback appreciated

2late
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Re: How to Build a keystick port internally to zx81

Post by 2late » Fri Apr 26, 2019 8:25 pm

I once had such a thing with at least 1 meter of cable and a connector on the 81. I may have been quite naive, but it worked.

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Re: How to Build a keystick port internally to zx81

Post by 2late » Sat Apr 27, 2019 4:34 pm

I should have noted, that this used no commercial joystick, but microswitches connected to the lines for the cursor keys.

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