Leaderboard

Here is the thing then: the 640 does work now with PC-Link and M-Crew. (See my uncut, lame video at the end - "Welcome to Paradise" :-) .) Yes, it is done, and I feel this is a breakthrough, after all those unsuccessful tries in the past, including my previous attempts back in 2017 or so. The icing on the cake is the 640 has kept all its keyboard functionalities too ! I guess what you are mostly interested in is how this was made possible, and what's needed to replicate it on your machines - the shiny, polished, step-by-step guide and documentation I originally wanted to post here can wait. The beauty is that it's like Columbus' egg. Plain and simple, and all of you will now say "gosh, I should have done this easily". [I had not reinvented the wheel either, really. What I did was I took the recently purchased S50's main board I did not fear to sacrifice and began doing actual measurements of what lines/signals go where, what connections, pull-up resistors, etc. are there, and compared the thing to the SM-s. The big surprise came when I realized none of the SM-s (640, S50, PC3, etc.) tell you the true story, because this or that is different here and there, from what is on paper and what is actually on the board. Looked too complex, and I got misled quite a few times when working only from the SM-s.] I distilled all this information down to a simple, clean solution. No matter which version you have (EU, US/CAN, etc.), just follow this: [In a nutshell: there is nothing special required, everything is there already in the machine (this was my theory afterall, and it finally stood). Very minor things must be checked and supplemented, but nothing that could not be done DIY.] Check this silly drawing: These are the lines (marked with green) that must be there, all the way from the PS2 socket down to the MCU (other lines are all there, nothing to do with them). Follow these lines on your actual boards/wires one by one and see if you can get there all along. If there are jumper wires and/or 0 ohm resistors and/or inductances in series, leave them there. If you see some pull-up (typically 4k7 or 10k) and/or pull-down resistors (typically 100k) or parallel capacitors, you can also leave them all there. If the continuity breaks somewhere, look after what is missing. What must be there in order to get this working, i.e., must be supplemented in case they are missing (and normally are - see my photos with the details below): - R36 and R37 (very tiny 0 Ohm resistors) are not populated on the main board (@sfbp, you have been this close, all the rest you did well!), - two wires are missing, from CN820 on the MB up to the keyboard pcb (as seen also on @sfbp's photos), making sure you solder them in proper order (do not accidentally swap them), and - two 100 ohm resistors need to be soldered on the keyboard PCB in the positions marked "L805" and "L806" (well, plain jumper wires would also work, but in some PC-Link models these serial resistances are there, for a reason I guess). (Warning: - when measuring traces on and wires between pcb-s, don't just use your DMM directly in resistance or continuity mode. See more on this here.) - make sure you and your device are properly ESD protected, and never work on a powered up machine.) This is it, and you're done. I would love to see then the feedback from people who succesfully replicated this on their machines. - - - Next steps that now are also doable using the same approach: - for "technical maximalism": build the I2C extender circuit mentioned above (good news: the keyboard PCB is already prepared just needs to be populated, and only THT parts are required), - probably the "most wanted" one: make the 940 work like the Japanese version, PC-Link and keyboard, - a "side effect": make the keyboard work on the S50 (and on the 470 too) - similary to the I2C buffer, the MB pcb already has this area, just unpopulated, - and an "opportunity" for the low end machines: make the 440 (!) work with PC-Link and even accept a keyboard too. And some mandatory, due thanks: - @kgallen - I value your attitude for getting things done quickly (like in the case of the copybit killer stuff). This pushed me out of my "laziness". - @sfbp - your photo gave me the final "kick" that my hypothesis was right, and that I had to finish my research and do the soldering part at last. When I saw your 640's main board, I immediately realized why your attempt was unsuccessful. (And I asked for some new photos because this very part was hardly visible caused by the bright spot of the flash, but then I came across finally even without them.) - @Sony - having these features already built in (only disguised for certain markets ...) MOV01439.MPG