exxos's Atari, Amiga & retro forum

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

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

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

Both ST and STf/e keyboard schematics for comparison:


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.

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

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...