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Any Electrical Engineers in the House?

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sandheaver:
I need advice on a way to turn the digital I/O of an arcade control panel into, basically, a combined digital connection where it would be turned back into discrete I/O for a JAMMA board on the other end.  The point is to create a much simpler harness-to-controls connection using a bit of automation.  Pulling power from the JAMMA harness is acceptable, this won't be a wireless solution.

At the moment I'm not interested in analog controls, such as trackballs or spinners; digital controls only.

Anyone know how I could do something like that?

MonMotha:
Are you willing/do you want to write a little firmware, or are you looking for something you can just build out of chips?

Or, are you looking for an off-the-shelf solution?

sandheaver:

--- Quote from: MonMotha on May 06, 2013, 05:49:02 pm ---Are you willing/do you want to write a little firmware, or are you looking for something you can just build out of chips?

Or, are you looking for an off-the-shelf solution?

--- End quote ---

I'm not one for assembly or C, but I can give it a go if required.  I don't know of an off-the-shelf solution.

MonMotha:
You can do this with a couple microcontrollers that have enough IO pins and just connect them via the UART.  Full Arduinos or similar dev boards would work (and have a somewhat more beginner-friendly programming environment), but they're cost-wise total overkill.

You can also do it using a bunch of shift registers and a little state machine built using some counters and glue logic.  Basically, you're building something resembling SPI but without a programmable controller.  This has the advantage of being essentially infinitely extensible since you just need more shift registers to add more IO, rather than more IO lines on a micro.  Of course, you can use IO expanders on a micro, too.

Another decent approach (that I might use) is something of a hybrid: use a micro on one end as the master and a bunch of shift registers on the other end as the slave.  This means you don't have to design the clock/state machine in hardware and can use the MCU's SPI controller for that instead. I2C IO expanders work, too, but I2C can sometimes be a pain.

There's of course a ton of other options.  These are just what come to mind off the top of my head, which generally means things I could implement using parts from my junk bin.  Your junk bin probably differs.  Most of the options I've described require 3-6 lines between both ends.  Parallel mux options also exist that wouldn't reduce the IO count as much also exist that may be a bit easier to implement in low integration (e.g. 74 series) hardware only.

sandheaver:
Will the dual microcontroller UART solution offer low enough latency?  hardware interrupts are probably the way to go if I know my interrupts.  Simple shift registers will do if they are fast enough, I suppose.

I don't know.  I'm in over my head a bit, here.

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