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Then, when should we use lookup ???
All this thread bring back a question that I had in mind for a while. I was wondering at which point is that better (faster) to use lookup instead of calculated values?
I know that I can find thread like "Sine wave power inverter" where a lookup table was used to increase calculation's speed. But is this only a trial an error process or can someone bring up guidelines that will lead to use one solution or the other?
J-P
Last edited by GrandPa; - 5th September 2007 at 04:48.
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One more thought . . . instead of 40 IF THEN loops would't SELECT CASE be more appropriate? I throw this out there, having NEVER used select case, because you see, I want to learn too . . .
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That would work, but that kind of division in PBP would take up a lot more processing time than the IF...THEN statements above.I'm sure that SELECT CASE could be used, or LOOKDOWN (or should it be LOOKUP?), depending on the strategy, and maybe more effectively than IF...THENs. In all of those cases, though, it still looks like a bulky approach. I'm still not convinced that the single 16-bit division isn't going to be not only simpler but faster.My question is: Why would doing that single division take longer than going through multiple IF...THEN statements (40-something of them in the example) until one is found where the condition is satisfied?
Thanks to whomever clarifies this for me!
Any thoughts? Is this one of those balancing acts between compact code and speed of operation?
Scott, how often do you need to update the display with new information?
Russ
N0EVC, xWB6ONT, xWN6ONT
"Easy to use" is easy to say.
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Here is all the IF/THENS in ASM
And here is the WORD division in ASM.Code:LABEL?L _convert_to_rpm CMPGE?BCL _z, 00Ah, L00001 MOVE?CB 000h, _rpm LABEL?L L00001 CMPNE?BCL _z, 00Ah, L00003 MOVE?CB 03Ch, _rpm LABEL?L L00003 CMPNE?BCL _z, 00Bh, L00005 MOVE?CB 037h, _rpm LABEL?L L00005 CMPNE?BCL _z, 00Ch, L00007 MOVE?CB 032h, _rpm LABEL?L L00007 CMPNE?BCL _z, 00Dh, L00009 MOVE?CB 02Eh, _rpm LABEL?L L00009 CMPNE?BCL _z, 00Eh, L00011 MOVE?CB 02Bh, _rpm LABEL?L L00011 CMPNE?BCL _z, 00Fh, L00013 MOVE?CB 028h, _rpm LABEL?L L00013 CMPNE?BCL _z, 010h, L00015 MOVE?CB 026h, _rpm LABEL?L L00015 CMPNE?BCL _z, 011h, L00017 MOVE?CB 023h, _rpm LABEL?L L00017 CMPNE?BCL _z, 012h, L00019 MOVE?CB 021h, _rpm LABEL?L L00019 CMPNE?BCL _z, 013h, L00021 MOVE?CB 020h, _rpm LABEL?L L00021 CMPNE?BCL _z, 014h, L00023 MOVE?CB 01Eh, _rpm LABEL?L L00023 CMPNE?BCL _z, 015h, L00025 MOVE?CB 01Dh, _rpm LABEL?L L00025 CMPNE?BCL _z, 016h, L00027 MOVE?CB 01Bh, _rpm LABEL?L L00027 CMPNE?BCL _z, 017h, L00029 MOVE?CB 01Ah, _rpm LABEL?L L00029 CMPNE?BCL _z, 018h, L00031 MOVE?CB 019h, _rpm LABEL?L L00031 CMPNE?BCL _z, 019h, L00033 MOVE?CB 018h, _rpm LABEL?L L00033 CMPNE?BCL _z, 01Ah, L00035 MOVE?CB 017h, _rpm LABEL?L L00035 CMPNE?BCL _z, 01Bh, L00037 MOVE?CB 016h, _rpm LABEL?L L00037 CMPGT?BCB _z, 01Bh, T1 CMPLT?BCB _z, 01Eh, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00039 MOVE?CB 015h, _rpm LABEL?L L00039 CMPNE?BCL _z, 01Eh, L00041 MOVE?CB 014h, _rpm LABEL?L L00041 CMPGT?BCB _z, 01Eh, T1 CMPLT?BCB _z, 021h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00043 MOVE?CB 013h, _rpm LABEL?L L00043 CMPGT?BCB _z, 020h, T1 CMPLT?BCB _z, 023h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00045 MOVE?CB 012h, _rpm LABEL?L L00045 CMPGT?BCB _z, 022h, T1 CMPLT?BCB _z, 025h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00047 MOVE?CB 011h, _rpm LABEL?L L00047 CMPGT?BCB _z, 024h, T1 CMPLT?BCB _z, 027h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00049 MOVE?CB 010h, _rpm LABEL?L L00049 CMPGT?BCB _z, 026h, T1 CMPLT?BCB _z, 02Ah, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00051 MOVE?CB 00Fh, _rpm LABEL?L L00051 CMPGT?BCB _z, 029h, T1 CMPLT?BCB _z, 02Dh, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00053 MOVE?CB 00Eh, _rpm LABEL?L L00053 CMPGT?BCB _z, 02Ch, T1 CMPLT?BCB _z, 031h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00055 MOVE?CB 00Dh, _rpm LABEL?L L00055 CMPGT?BCB _z, 030h, T1 CMPLT?BCB _z, 035h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00057 MOVE?CB 00Ch, _rpm LABEL?L L00057 CMPGT?BCB _z, 034h, T1 CMPLT?BCB _z, 03Ah, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00059 MOVE?CB 00Bh, _rpm LABEL?L L00059 CMPGT?BCB _z, 039h, T1 CMPLT?BCB _z, 040h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00061 MOVE?CB 00Ah, _rpm LABEL?L L00061 CMPGT?BCB _z, 03Fh, T1 CMPLT?BCB _z, 047h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00063 MOVE?CB 009h, _rpm LABEL?L L00063 CMPGT?BCB _z, 046h, T1 CMPLT?BCB _z, 051h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00065 MOVE?CB 008h, _rpm LABEL?L L00065 CMPGT?BCB _z, 050h, T1 CMPLT?BCB _z, 05Dh, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00067 MOVE?CB 007h, _rpm LABEL?L L00067 CMPGT?BCB _z, 05Ch, T1 CMPLT?BCB _z, 06Eh, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00069 MOVE?CB 006h, _rpm LABEL?L L00069 CMPGT?BCB _z, 06Dh, T1 CMPLT?BCB _z, 086h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00071 MOVE?CB 005h, _rpm LABEL?L L00071 CMPGT?BCB _z, 085h, T1 CMPLT?BCB _z, 0ACh, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00073 MOVE?CB 004h, _rpm LABEL?L L00073 CMPGT?BCB _z, 0ABh, T1 CMPLT?BCB _z, 0F1h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00075 MOVE?CB 003h, _rpm LABEL?L L00075 CMPGT?BCB _z, 0F0h, T1 CMPLT?BCB _z, 00191h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00077 MOVE?CB 002h, _rpm LABEL?L L00077 CMPGT?BCB _z, 00190h, T1 CMPLT?BCB _z, 004B1h, T2 LAND?BBW T1, T2, T2 CMPF?WL T2, L00079 MOVE?CB 001h, _rpm LABEL?L L00079 CMPLE?BCL _z, 004B0h, L00081 MOVE?CB 000h, _rpm LABEL?L L00081 GOTO?L _convert_to_rpm
Do not know about CASE either.Code:LABEL?L _TEST MOVE?CW 003E8h, _FREQ MOVE?CW 010h, _SPEED DIV?WWW _FREQ, _SPEED, _ROTATIONS GOTO?L _TEST
Last edited by mackrackit; - 5th September 2007 at 21:32.
Dave
Always wear safety glasses while programming.
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Thanks, Dave! That was a lot of extra effort to answer the question, but I appreciate it. I'm sure others will, too!
Scott--what do you think?
Last edited by RussMartin; - 5th September 2007 at 23:31.
Russ
N0EVC, xWB6ONT, xWN6ONT
"Easy to use" is easy to say.
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No problem, PBP did all of the work.
Dave
Always wear safety glasses while programming.
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Russ...The 60000 math thing worked great. The digits changing on the LCD actually looks quite natural and "smooth". It doesn't look jerky. It is faster that you can read.
I applied all of this to another project where I am driving a stepper motor as a position indicator, ie. a needle on a scale. I am quite satisfied with it.
The only issue I see with my current calculations is that a change in a millisecond at the high end of the scale represents a larger change in RPM than a millisecond does at the lower speeds. This makes the needle seem a bit twitchy at the higher speeds. I plan to see what I can do to improve that somewhat.
I initially attempted this project using COUNT . It worked, but moving the needle was painfully slow.
Thanks for all the input
Scott
Last edited by chips123; - 6th September 2007 at 02:54.
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