Keyboard swap

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Bikerbob
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Keyboard swap

Post by Bikerbob »

Trying to put a mega (mechanical switch) keyboard in a 520ST

Simply swaping the keyboard does not work..

I cannot find a 520ST - original 520ST no F no M .. nothing.. schematic for the keyboard.

Anyone?


James
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Icky
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Re: Keyboard swap

Post by Icky »

@Bikerbob - there is a schematic here https://www.exxosforum.co.uk/forum/viewt ... 021#p24207
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Bikerbob
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Re: Keyboard swap

Post by Bikerbob »

Thanks Icky. but I already know that one does not match the original 520ST.

The orginal 520ST has a RESET wire in the header. I have figured it out with this 520ST_SAMS_Computerfacts_CSCS12_08974

What I dont know.. is it ok to operate that keyboard without the reset line.. I am not sure what it is resetting.. maybe the keyboard clock?

But everything later does not have that reset line. It is green.. and the last one on the keyboard header.

James
tzok
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Re: Keyboard swap

Post by tzok »

Both ST and STf/e keyboard schematics for comparison:
Image Image

All ST keyboards were electrically the same (from the ST side), only the ST keyboard had re-routed JOY0/1 signals to the motherboard.

\RESET is an input signal for K/B, it resets the IKBD MCU.It should be connected, as IKBD sends some data to ST after reset, but in most cases it will work without it.
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Bikerbob
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Re: Keyboard swap

Post by Bikerbob »

So if the reset was removed later why is that? Just asking?

I have got them both working.. without the reset connected. If I do connect it.. just run a jumper wire from the header pin to the pin on the chip?

Also your one diagram there is showing all 18 pins used.. I have no keyboard between the two where pin 18 is wired up.. no idea where that diagram is from.

James
tzok
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Re: Keyboard swap

Post by tzok »

18 wires were used on a "short" ST, in order to route JOY/MOUSE port signals to the connectors on the mainboard. All later models had these connectors on the keyboard PCB.

Every ST (short) and STf/m/e and Falcon keyboard has a \RESET line wired...
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