[Bulk] Re: [Diy_efi] Modular approach to EFI controllers

Mike niche
Mon Oct 1 10:20:12 UTC 2007


This raises more questions that it answers  ;-)

Do you have a base data flow analysis ah la work schedule type
format sequence of events as very little of what goes on is anywhere
near coincident even on a W16 - I do but hazard a guess ?

Eg. How many V12's have coincident ignition or sequential fueling
and even then an interrupt condition properly prioritized looks after just
so much...

BTW: Curious, does the W16 have a coincident firing event ?



At 05:30 PM 10/1/07, you wrote:
>On Mon, 2007-10-01 at 10:49 +0800, Mike wrote:
>> Is the FPGA that necessary, I mean, with a fast enough processor
>> and the appropriate software it should be a chince, even if you had
>> a second CPU doing nothing but  the timing and ion sensing etc,
>> you are not going to have the spark events coincident so surely
>> with a CPU even doing 4Mhz there is enough time, these beasts
>> are cheap have good a/d and run 20Mhz etc... 
>Oh yes. very necessary.
>ok, so we overspecc'd it a bit so it can handle (in theory) a W16 engine
>configuration with twin spark and twin injector multiport injection, but
>the math worked out upwards of 90,000 events per second at redline.
>you *could* handle all that on a 20Mz CPU perhaps, but then if theres
>one error in that and you lean out at 15,000 RPM or so its bye-bye
>engine. much better to have a nice simple state machine do the job
>predictably and without bothering the CPU.
>if you actually want to _do_ anything with the ion sense data you're
>looking at doing thousands of FFTs per second, which starts to really
>rack up the amount of CPU grunt you need - and with heavy processing
>would come high latency, or the need to design _very_ tight real time
>Much easier to have the FPGA do the critical stuff and simply pass data
>to the ARM for analysis and receive feedback to modify its controll
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Regards from

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