Cable info to connect a Mega ST keyboard to a standard ST

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JezC
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Cable info to connect a Mega ST keyboard to a standard ST

Post by JezC »

Hi, I'm hoping someone can help point me in the right direction.

I've got an original Mega ST keyboard & used to have this connected into a stock ST with an adaptor cable.

Sadly I've yet to find this cable :roll: & want to use the Mega keyboard with an ST (which has a broken keyboard) so I was wondering if anyone can provide the wiring info I would need to make a new cable (or two).

I believe that others are also interested in these details so if I find the lead I will obviously spread the knowledge.

TIA
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DoG
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Re: Cable info to connect a Mega ST keyboard to a standard ST

Post by DoG »

Keyboard connectors all Ataris.png
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JezC
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Re: Cable info to connect a Mega ST keyboard to a standard ST

Post by JezC »

Fantastic!
I'll trawl through my parts and order up anything I'm missing.
Thanks for the info, much appreciated. :D
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rubber_jonnie
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Re: Cable info to connect a Mega ST keyboard to a standard ST

Post by rubber_jonnie »

Thought I'd add this as I need to build an adapter, hopefully it'll help somebody else too.

Mega_2_ST_KBD_Corrected.png
Mega_2_ST_KBD_Corrected.png (31.26 KiB) Viewed 8113 times

EDIT: 04/04/2020 Picture corrected to show correct TX/RX connection
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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DoG
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Re: Cable info to connect a Mega ST keyboard to a standard ST

Post by DoG »

It seems that my first post is a bit wrong. Tx should connect to Rx for it to work. And Rx to Tx. Would be great if you could confirm this and update us when you have tested the cable.

So pin 5 on the Atari to pin 3 on the RJ12 (MegaST connector).
Pin 6 on the Atari to pin 4 on the RJ12.


Mega ST keyboard connector pinout.jpg
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keyboard schematics Atari ST.jpg
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rubber_jonnie
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Re: Cable info to connect a Mega ST keyboard to a standard ST

Post by rubber_jonnie »

@DoG Cool I am hoping to have a look at this over the weekend, I'll let you know and I'll update my diagram too.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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rubber_jonnie
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Re: Cable info to connect a Mega ST keyboard to a standard ST

Post by rubber_jonnie »

So, what with postal delays, my RJ12 sockets literally just arrived today, so hopefully over the weekend I can have a look at wiring something up.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Steve
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Re: Cable info to connect a Mega ST keyboard to a standard ST

Post by Steve »

Yeah I can confirm dogs picture has that tx rx error, when I was building my rj12 port on my falcon for an external keyboard it really confused me at the time.

http://atari-forum.com/viewtopic.php?f=27&t=37822

Here is my process as I did troubleshooting. Might be helpful.
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rubber_jonnie
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Re: Cable info to connect a Mega ST keyboard to a standard ST

Post by rubber_jonnie »

Cool, thanks @Steve
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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rubber_jonnie
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Re: Cable info to connect a Mega ST keyboard to a standard ST

Post by rubber_jonnie »

Hmm, into head scratching mode now. I've wired up an RJ12 socket as follows:

Mega_2_ST_KBD_Corrected.png
Mega_2_ST_KBD_Corrected.png (31.26 KiB) Viewed 8028 times

The keyboard has power as the power LED is lit, but it's not working when plugged into my Mega ST. I've tried reversing the TX/RX connections as mentioned further up the post but no different.

I'm now wondering, that as I'm trying to connect the opposite way i.e. STFM KBD to Mega ST, if it actually works in reverse. I'd expect it should, but if anyone has any ideas I'd be grateful.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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