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Unread 24-04-2008, 17:44
Dave Flowerday Dave Flowerday is offline
Software Engineer
VRC #0111 (Wildstang)
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Re: NEW 2009 Control System Released

Quote:
Originally Posted by dcbrown View Post
By committing the time critical processing to hardware, this eliminates the need for interrupts to service the hardware events and makes time sliced multitasksing that polls & processes the data viable.
...except only the things that FIRST and/or NI has thought of are committed to hardware. Since the FPGA is not user-programmable, any novel ideas or sensors which would need interrupt support are not possible - I think this is what Alan was getting at above. In my opinion this is a HUGE step backwards from the current control system and a very disappointing revelation.

A perfect example occurred this year - the FIRST-supplied IR receiver sucked, so Kevin whipped up some code that allowed you to do it on the RC with a simple receiver plugged into an interrupt port. I don't see how that would be possible in a new system that does not support interrupts. Sure, IR happens to be slow enough that you might be able to poll for it (remember, your polling frequency is going to be limited by your OS tick rate and if multitasking it may not be constant), but it doesn't take much imagination to think up other instances where something like this is not possible. And, if you start polling for enough things, all that nice extra MHz provided by the new processor will be chewed up doing menial tasks which are handled in hardware for free basically by a $5 PIC.

A few years ago myself and a few other mentors from Wildstang along with a few from the Technokats investigated using an optical mouse for tracking position. We did this by bit-banging the non-standard synchronous serial protocol used by the chip inside the mouse on the RC hardware. This is another example of something that might be difficult or impossible under the new system without interrupts.
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