Let me start with a disclaimer: I don't own an LK201, so I may be wrong about some things.
I do own an MC7004 russian model F clone keyboard, and some sources state that it has the same protocol as the LK201.
See this doc for a description of the LK201 protocol:
http://www.netbsd.org/docs/Hardware/Mac ... troduction
Electrically speaking you can't use a soarer's to talk to it, however you could use an RS232-to-USB converter like this:
https://assets.aten.com/product/image/u ... ers.45.jpg
It needs an rs232 converter that is using real rs232 signal levels, not a TTL-level converter. (so you can't use those rs232 adapter cables that people use to talk to microcontrollers. You need an rs232 converter that has a DB9 port on it, usually only those include the signal level shifters). Or you could use the native RS232 on your system in case you have such a thing.
Other than an RS232 converter you will also need a 11.8V +-6% power supply.
This won't just work out-of-the box, cause the operating system can't auto-detect that there is a keyboard attached to your serial port. On linux there is already software to talk to the LK201 keyboard. See "inputattach -lk".
I have tried "inputattach -lk" with the MC7004 keyboard, with a converter like above, and a 12V power supply:
- trying_with_rs232.jpg (44.59 KiB) Viewed 2550 times
The result is not great, but it's also not a complete failure either: After I press a key, I do see the correct key being typed in linux, but the key is never released, so the os's repeat function comes in, and I just get a long string of the pressed key. This could have multiple reasons:
1) Maybe the MC7004 is only kindof compatible with LK201, and maybe it's missing some features. I think this is the most likely.
2) Maybe my MC7004 keyboard is damaged.
3) Maybe the inputattach code is buggy and needs some modification.
I think 1) is the most likely, so it will probably work fine with a real LK201.
I also started a little project to make a converter for LK201 and MC7004 keyboards, that would show up as a USB keyboard to the host, and that you wouldn't need to run software such as inputattach. It's basicly a pro micro + max232 level shifter IC + a boost converter:
- converter.png (182.31 KiB) Viewed 2550 times
It got as far as ordering some PCBs from JLCPCB, but my first prototype didn't work as I expected, mainly because of the current consumption of the keyboard. I ordered the pcbs before even receiving the MC7004 keyboard. Looks like the LK201 is specified to consume 350 mA, and the mc7004 was specified to 500mA, and my thinking was: no way can a keyboard consume so much current @ 12 Volts, it must be less than 100mA, so I can use a boost converter to drive it off of a single USB port, and I just ignored the spec, I didn't believe it. Lesson learned, when you don't follow the spec, you support the consequences. The MC7004 keyboard I actually measured to consume 340mA. So there's no chance for the first version of my project to work.
So I temporarily left it there, at some point I will pick it up again, and make a version of it that requires an external 12V power supply. Or maybe I'll just mod a few of the boards to remove the useless boost converter, and add a DC jack. I just find it annoying that there's no way to convert it without an external power supply.