A speed-tatstic way to look up a value? (LUTs)

[cncmachineguy]

Hank, if it works dont fix it. or if it isn't broke, fix it till it is. lol

Seriously, the only thing i would do is make sure and run your test from the bottom up. By this I mean, check for the low count first on up th to highest count. then you can be sure to have enough time. . Something else about your linear search, Y only need to test for 1 condition in each next IF after the first. heres why:

First check establishes a range, say 3800-3900, if this fails, number must be > 3900. next check just needs to look for <4000 cuz you know its >3900. next check if <4200,again because it must be >3900. and so on. Of course my numbers are fictious, but you should get the point. Only checking 1 condition should almost double the execution speed (half the processing).

the code I posted is not complete, it shows how to go through the levels of searching.

[HankMcSpank]

Well the acid test is when I play a guitar into it & the pic 'triggers' a sound in midi synth module.

A bass E string 'period' is about 12ms (82.4Hz) ....add in the overhead that detecting the frequency will entail, then it's going to be higher.

They reckon the average musician can detect about 10ms of latency (ie from hitting a key, banging a drum,plucking a string .... to actually hearing the sound) so I'm already behind the curve so to speak. The commercial 'guitar to midi' converters pull this frequency 'detection time' in by detecting half a period....so for 82.4Hz, that'd be about 6ms - safely under the 10ms level - but I reckon that'd need a 40Mz oscillator to have the necessary granularity.

So perhaps it's better to go top down (the bass frequencies are at the top of the list), just to rescue back a little bit of 'processing time' for those lower frequencies (for example a 1Khz 'period' is 1ms, so I've far more time to play with vs lower frequencies.)