How to make "Larry's" Casio PC-link Cable.

We've made almost one million of these cables for Casio!

Here you can learn how the circuit works, thanks to the US Patent Office. Disclosure is the core idea behind a Patent in the first place! Did you know? Patents are supposed to teach you how an invention works! In exchange for sharing the idea, the USA grants the inventor some rights for a few years with the idea he/she can profit from it. Like a reward for being open. What a concept! You wouldn't think this looking at most patents. Most look as if the goal was to confound the reader not enlighten her or him. Anyway, you can use all the knowledge presented in them. You can make things for your own use if you do not sell it or otherwise profit from it's use. (note: 12/99 - oops, I'm wrong, a patent "grants ... rights to exclude others from making, using, offering to sell, selling, or importing the invention ...", in the USA. Ha! My mistake. However, I don't think anyone will sue you for makeing one for your own use, besides if you just want a cable it's way easier and less expensive to buy one from me, so we must assume that if you make one, it's more for your education than saving money, even though technically you would be infringing the patent, it is impossible for anyone to stop you. If you feel bad about infringing, send $5 to me to cover my lost profit. I'll tell the world about it here, about someone who beleives in inteculactual property rights enough to send $5 to me. Wow, that would be international news! Anyway all patent ideas and the "how-to" information are public and free! What a deal. I like free. Free is good. Freedom built America and it is now building the internet! So build this cable and learn how it works. Learn why Casio uses this circuit in all their PC-link products, even for their new cool digital cameras.

Go here to see: My patent. (assigned back to me)

Here you can buy one already made: FOR-SALE page.

Here is page #3 of the patent:

If you want to build this and need some hard to find parts, I have them here and will send you some, for free!

New things about the circuit:

R7, R8, and R2 are not needed and D2 is only for some ESD protection so any value over 6V will work. Q1 can be any NPN like a 2N2222 however Q2 is a P channel FET and must be matched up with D1 to set the threshold to a proper level. R3 is there only to reduce RFI emitting from the Casio. Together with R1 and R6 it is effective only if the circuit is placed close to the Casio unit (a inch or two is cool). If this is not done, then RFI emmisions should be addressed with a large ferrite bead. If you don't care about RFI or you would rather add large ferrite beads to the cable, you can leave out R3 and connect ground to ground. Some copy-cat cables did this and ended up being like V--ger from Star Trek by the time they got through FCC and CE-Mark. Pretty funny. That'll teach 'em. Ha! Maybe not. R6 can be from 2k to 10k depending on the Q2 and D1 selection. If you leave out R2 then size R1 at 10k. The only reason we had R2 in there was to make a voltage divider because we wanted to use a SIP and so could not make R1 the value we wanted. A good value for R5 is 4.7k. You can put R5 on the PCB but will then need a 5 wire cable. You can put the PCB inside the DB9 but you'll need to pull up R to avoid cable coupling but the pull-up will draw current form the Casio which defeats a very important feature of the circuit and will cost you a lot replacing batteries. There are many multi-level syneregies here that make the ciruict really fun to study when you consider the functional, economic, political (FCC, CE), and aestheic aspects all at the same time. Have fun and if you have any questions, just ask.

mybest, larry,

A nice image of the PCB and parts has been done here: Casio Corner If there are other sites that reference this page or the patent, please tell me.

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