71 lines
2.8 KiB
C
71 lines
2.8 KiB
C
/*
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These are some utility functions and variables used through the main code
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*/
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#include <Arduino.h>
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#define MS_IN_MINUTE 60000
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#define US_IN_MINUTE 60000000
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/*
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Returns how much free dynamic memory exists (between heap and stack)
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*/
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int freeRam ()
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{
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extern int __heap_start, *__brkval;
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int v;
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return (int) &v - (__brkval == 0 ? (int) &__heap_start : (int) __brkval);
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}
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/* The following functions help determine the required fuel constant. For more information about these calculations, please refer to http://www.megamanual.com/v22manual/mfuel.htm
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Calc below are for metric inputs of temp (degrees C) and MAP (kPa) to produce kg/m3.
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*/
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int AIRDEN(int MAP, int temp)
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{
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return (1.2929 * 273.13/(temp+273.13) * MAP/101.325);
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}
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/*
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This function retuns a pulsewidth time (in us) using a either Alpha-N or Speed Density algorithms, given the following:
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REQ_FUEL
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VE: Lookup from the main MAP vs RPM fuel table
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MAP: In KPa, read from the sensor
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GammaE: Sum of Enrichment factors (Cold start, acceleration). This is a multiplication factor (Eg to add 10%, this should be 110)
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injDT: Injector dead time. The time the injector take to open minus the time it takes to close (Both in uS)
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TPS: Throttle position (0% to 100%)
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This function is called by PW_SD and PW_AN for speed0density and pure Alpha-N calculations respectively.
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*/
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unsigned int PW(int REQ_FUEL, byte VE, byte MAP, int corrections, int injOpen, byte TPS)
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{
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//Standard float version of the calculation
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//return (REQ_FUEL * (float)(VE/100.0) * (float)(MAP/100.0) * (float)(TPS/100.0) * (float)(corrections/100.0) + injOpen);
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//100% float free version, does sacrifice a little bit of accuracy. Accuracy loss is in the order of 0.1ms (100uS)
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int iVE = ((int)VE << 7) / 100;
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int iMAP = ((int)MAP << 7) / 100;
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int iCorrections = (corrections << 7) / 100;
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int iTPS = ((int)TPS << 7) / 100;
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unsigned long intermediate = ((long)REQ_FUEL * (long)iVE) >>7; //Need to use an intermediate value to avoid overflowing the long
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intermediate = (intermediate * iMAP) >> 7;
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intermediate = (intermediate * iCorrections) >> 7;
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intermediate = (intermediate * iTPS) >> 7;
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unsigned int final = (unsigned int)(intermediate + injOpen);
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//if (final > 65535) { final = 65535; } //Make sure this won't overflow. This means the maximum pulsewidth possible is 65.535mS
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return final;
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}
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//Convenience functions for Speed Density and Alpha-N
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unsigned int PW_SD(int REQ_FUEL, byte VE, byte MAP, int corrections, int injOpen)
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{
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return PW(REQ_FUEL, VE, MAP, corrections, injOpen, 100); //Just use 1 in place of the TPS
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}
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unsigned int PW_AN(int REQ_FUEL, byte VE, byte TPS, int corrections, int injOpen)
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{
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//Sanity check
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if(TPS > 100) { TPS = 100; }
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return PW(REQ_FUEL, VE, 100, corrections, injOpen, TPS); //Just use 1 in place of the MAP
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}
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