113 lines
4.3 KiB
C
113 lines
4.3 KiB
C
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// TI File $Revision: /main/6 $
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// Checkin $Date: August 9, 2007 17:14:59 $
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//###########################################################################
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//
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// FILE: Example_freqcal.h
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//
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// TITLE: Frequency measurement using EQEP peripheral
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//
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// DESCRIPTION:
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//
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// Header file containing data type and object definitions and
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// initializers.
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//
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//###########################################################################
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// Original Author: SD
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//
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// $TI Release: DSP2833x/DSP2823x Header Files V1.20 $
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// $Release Date: August 1, 2008 $
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//###########################################################################
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#ifndef __FREQCAL__
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#define __FREQCAL__
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#include "IQmathLib.h" // Include header for IQmath library
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/*-----------------------------------------------------------------------------
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Define the structure of the FREQCAL Object
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-----------------------------------------------------------------------------*/
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typedef struct {
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Uint32 freqScaler_pr; // Parameter : Scaler converting 1/N cycles to a GLOBAL_Q freq (Q0) - independently with global Q
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Uint32 freqScaler_fr; // Parameter : Scaler converting 1/N cycles to a GLOBAL_Q freq (Q0) - independently with global Q
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Uint32 BaseFreq; // Parameter : Maximum Freq
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_iq freq_pr; // Output : Freq in per-unit using capture unit
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int32 freqhz_pr; // Output: Freq in Hz, measured using Capture unit
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Uint32 oldpos;
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_iq freq_fr; // Output : Freq in per-unit using position counter
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int32 freqhz_fr; // Output: Freq in Hz, measured using Capture unit
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void (*init)(); // Pointer to the init funcion
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void (*calc)(); // Pointer to the calc funtion
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} FREQCAL;
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/*-----------------------------------------------------------------------------
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Define a QEP_handle
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-----------------------------------------------------------------------------*/
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typedef FREQCAL *FREQCAL_handle;
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/*-----------------------------------------------------------------------------
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Default initializer for the FREQCAL Object.
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-----------------------------------------------------------------------------*/
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#if (CPU_FRQ_150MHZ)
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#define FREQCAL_DEFAULTS {\
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234,200,10000,0,0,\
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0,0,0,\
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(void (*)(long))FREQCAL_Init,\
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(void (*)(long))FREQCAL_Calc }
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#endif
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#if (CPU_FRQ_100MHZ)
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#define FREQCAL_DEFAULTS {\
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313,200,10000,0,0,\
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0,0,0,\
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(void (*)(long))FREQCAL_Init,\
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(void (*)(long))FREQCAL_Calc }
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#endif
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/*-----------------------------------------------------------------------------
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Prototypes for the functions in Example_freqcal.c
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-----------------------------------------------------------------------------*/
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void FREQCAL_Init(void);
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void FREQCAL_Calc(FREQCAL_handle);
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#endif /* __FREQCAL__ */
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/* Notes:
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For 150 MHz Operation:
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----------------------
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1. freqScaler_fr
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v = (x2-x1)/T - Equation 1
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If max/base freq = 10kHz: 10kHz = (x2-x1)/(2/100Hz) - Equation 2
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max (x2-x1) = 200 counts = freqScaler_fr
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Note: T = 2/100Hz. 2 is from (x2-x1)/2 - because QPOSCNT counts 2 edges per cycle
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(rising and falling)
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freqhz_fr = 200 default
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2. min freq = 1 count/(2/100Hz) = 50 Hz
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3. freqScaler_pr
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v = X/(t2-t1) - Equation 4
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If max/base freq = 10kHz: 10kHz = 8/(2T)
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where 4 = QCAPCTL [UPPS] (Unit timeout - once every 4 edges)
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T = time in seconds = t2-t1/(150MHz/128), t2-t1= # of QCAPCLK cycles, and
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1 QCAPCLK cycle = 1/(150MHz/128)
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= QCPRDLAT
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So: 10 kHz = 4(150MHz/128)/2(t2-t1)
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t2-t1 = 4(150MHz/128)/(10kHz*2) = (150MHz/128)/(2*10kHz/4) - Equation 5
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= 234 seconds = maximum (t2-t1) = freqScaler_pr
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freqhz_pr = 234 default
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For 100 MHz Operation:
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----------------------
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The same calculations as above are performed, but with 100 MHz
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instead of 150MHz when calculation freqhr_pr, and at UPPS of 8 instead of 4.
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The value for freqScaler_pr becomes: (100MHz/128)/(2*10kHz/8) = 313
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More detailed calculation results can be found in the Example_freqcal.xls
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spreadsheet included in the example folder.
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*/
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