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Which is better - I-pac or KeyWiz keyboard encoder?

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protokatie:


--- Quote ---I may be wrong here, but I'd have thought it would have to be scanning the PS2 Pass-through in order to know if a key on the keyboard has been pressed?? can you explain why that's not the case please.
--- End quote ---

Im sure Andy's reply above was better than this one, but in the docs for the chip it mentioned as one of the features that it had circuitry built on the chip that did the detection of USB/PC as well as formatting the output to the detected type. This is from my memory from a month ago, but it did seem to mention actual dedicated circuitry for that. I could post some links to the docs online, but I dont know if Andy would appreciate it if I did. Even tho he doesnt actively censor what chips he uses are, I think I will leave it up to people to do their own detective work...

AndyWarne:


--- Quote from: Fozzy The Bear on February 01, 2008, 10:29:47 am ---
Now that's interesting Andy. Can you explain how it achieves that?? I may be wrong here, but I'd have thought it would have to be scanning the PS2 Pass-through in order to know if a key on the keyboard has been pressed?? can you explain why that's not the case please.

Best Regards,
Julian (Fozzy The Bear)

--- End quote ---

OK heres how it works:
The pass-through input consists of a clock and a data line as you probably know. The chip is set to generate an interrupt every time the clock line goes low.
The interrupt routine drives a bit-level state counter which clocks in each bit of the pass-through keyboard data using a state machine. So it can do this while doing its other tasks. There is also a byte-level state machine which assembles the processed byte.
So, when the keyboard is idle, no interrupts are generated and no processing is required by the pass through. It is not polled at all.
Even when the keyboard is in use, there is very little overhead as the interrupt routine which clocks in the bits is very short.
Andy

AndyWarne:


--- Quote from: protokatie on February 01, 2008, 08:22:24 pm ---
 I could post some links to the docs online, but I dont know if Andy would appreciate it if I did. Even tho he doesnt actively censor what chips he uses are, I think I will leave it up to people to do their own detective work...

--- End quote ---
I would not mind at all. The I-PAC uses the Cypress CY7C63413 chip. But this is like saying "This blank CD-R I have bought means I can now produce a hit album". The chip is blank when purchased, there is the small matter of developing all the code to program into it. In fact the ROM on that chip is crammed full, the additional features of the I-PAC such as the self-test LED which indicates wiring problems, the built-in interactive programming, the dual PS/2 USB interface, keyboard LED support and active pass-through add up to a lot of code. But the core code which is used in actual gameplay is compact of course.
In fact regarding the auto-detection of the interface type, this is not built into the chip at all, its coded. I worked closely with a Cypress development engineer with getting that piece of code right and the resulting enhancements found their way into Logitech dual-interface keyboards.
Its easy to see from a picture of the Keywiz that it uses the same chip (although they seem to sand off the part numbers on their chips for some strange reason) but its a different animal of course, different coding.

Teknique:

I use both an ipac4 and 2x 49way wiz (similar to keywiz) encoders.  Maybe it is because I play with the ipac more but I found the 49way inputs less intuitive especially the use of the shazamm /shift feature.     
I  like the added control I get with plugging in my keyboard to the ipac and doing diagostic type stuff like checking for shorts or bad cherry switches.  That said, I am very pleased with my 49way encoders as well and would buy them again to use just for the joysticks... even though they have additional inputs that can be used.  For general keyboard encoder fuctions though, Id buy an ipac again.

Tek




Fozzy The Bear:


--- Quote from: AndyWarne on February 02, 2008, 05:12:37 am ---OK heres how it works:

--- End quote ---

Thanks Andy.... I get it now.... It's running a separate state counter. Cool bit of coding.

I'm just about to start using the Cypress chips on another project that has nothing to do with arcade machines. They really are very adaptable little beasts. I notice they incorporated your passthrough and auto interface detection directly into some of their other chips now. They should be paying you a development fee ROFL  :laugh2:

Best Regards,
Julian (Fozzy The Bear)

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