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Re: ProblemwithPWMfrequency
Hi,
1) Can't help without seeing the values.
2) Not sure I understand what the problem is.... If you want a certain maximum dutycycle then simply rescale the values before storing them in the lookuptable (change the formula to produce a table with lower values). If you want to rescale at runtime then you need to perform the math in the PIC. Retrieve the "original" value, rescale, and output.
/Henrik.
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Re: ProblemwithPWMfrequency
Hi HenrikOlsson
1) Can't help without seeing the values.
Here is the values
Code:Wsave var byte $70system Wsave1 var byte $A0system Wsave2 var byte $120system Wsave3 var byte $1A0system STEPCOUNT var byte STEPCOUNT1 var byte LED1 VAR PORTB.1 STEPCOUNT = 0 'pointer for phase one in sinearray STEPCOUNT1 = 12 'pointer for phase two in sine array ADCON0 = %00000000 ADCON1 = %00000000 TRISB = %11111101 TRISC = %11111001 'PMW output for CCP1 AND CCP2 TRISA = %11111111 TMR2 = 0 PR2 = 199 'generate 5khz 'set for 18Khz HPWM CCP1CON = %00001100 'set CCP1 for PWM OPERATION CCP2CON = %00001100 'set CCP2 for PWM OPERATION T2CON = %00000100 'TIMER2ON and prescale of 1:1 sineval var byte[36] sineval[0] = 512 sineval[1] = 583 sineval[2] = 652 sineval[3] = 717 sineval[4] = 775 sineval[5] = 825 sineval[6] = 866 sineval[7] = 896 sineval[8] = 915 sineval[9] = 921 sineval[10] =915 sineval[11] =896 sineval[12] =866 sineval[13] =825 sineval[14] =775 sineval[15] =716 sineval[16] =652 sineval[17] =583 sineval[18] =512 sineval[19] = 441 sineval[20] = 372 sineval[21] = 308 sineval[22] = 249 sineval[23] = 199 sineval[24] = 158 sineval[25] = 128 sineval[26] = 109 sineval[27] = 103 sineval[28] = 109 sineval[29] = 128 sineval[30] = 158 sineval[31] = 199 sineval[32] = 249 sineval[33] = 308 sineval[34] = 372 sineval[35] = 441 timerone var word Temp var byte Temp1 var byte INCLUDE "DT_INTS-14.bas" ; Base Interrupt System emp 'INCLUDE "ReEnterPBP.bas" ASM INT_LIST macro ; IntSource, Label, Type, ResetFlag? INT_Handler TMR1_INT, _sine, ASM, yes endm INT_CREATE ; Creates the interrupt processor ENDASM T1CON = 000001 ; Prescaler = 1;1, TMR1 ON @ INT_ENABLE TMR1_INT ; Enable Timer 1 Interrupts timerone = 65080' gives1818hz nterruptfrequency or about 50 htz sine Main: PAUSE 5 GOTO Main '---[TMR1_INT - interrupt handler]------------------------------------------ sine: T1CON = 000000 'stop the timer TMR1L = timerone.byte0 'reload the timer TMR1H = timerone.byte1 T1CON = 000001 ' start the timer TeMP = sineval[STEPCOUNT] CCP1CON.4 = Temp.0 ' bit 0 CCP1CON.5 = Temp.1 ' bit 1 CCPR1L = Temp >>2 'Bit 2-7 TeMP1 = sineval[STEPCOUNT1] CCP2CON.4 = Temp1.0 ' bit 0 CCP2CON.5 = Temp1.1 ' bit 1 CCPR2L = Temp1 >>2 'Bit 2-7 TOGGLE LED1 stepcount = stepcount +1 stepcount1 = stepcount1 +1 if stepcount =36 then stepcount =0 if stepcount1 =36 then stepcount1 =0 @ INT_RETURN
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Re: ProblemwithPWMfrequency
Hi,
Here's three cycles with the values from you last post.
What is that you think is wrong with it? I don't see it...
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Re: ProblemwithPWMfrequency
He checks for 36, shouldn't it be 35?
Robert
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Re: ProblemwithPWMfrequency
No, after completing step 35, it increments, then it does a = 36 check. If it = 36, it goes back to step 0.Originally Posted by Demon
http://www.scalerobotics.com
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Re: ProblemwithPWMfrequency
Right, I forgot to check when the step was incremented, argh, and that's basic debugging procedure too (must be going senile).
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Re: ProblemwithPWMfrequency
Could the length of PAUSE be an issue?
http://www.picbasic.co.uk/forum/showthread.php?t=1853
Would placing PAUSE 1 within a loop make a difference?
What about using microseconds instead of milliseconds?
There's a minimum delay in microseconds in the PBP manual, but I don't see oscillator setting in that last code.
Robert
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Re: ProblemwithPWMfrequency
No change even if the pause 1, what I want to ask is the values in the look table greater than 255 may affect the sinwave and cause the signal to be distorted?. Can any one simulates the code and see the effect. Why the output look like this because I have try to eliminate the problem of flat spot for almost 4days but the problem still exit even although I try to edit my look table as HenrikOlsson told me about the value 512 ).
Code:define OSC 4 Wsave var byte $70system Wsave1 var byte $A0system Wsave2 var byte $120system Wsave3 var byte $1A0system STEPCOUNT var byte STEPCOUNT1 var byte LED1 VAR PORTB.1 STEPCOUNT = 0 'pointer for phase one in sinearray STEPCOUNT1 = 12 'pointer for phase two in sine array ADCON0 = %00000000 ADCON1 = %00000000 TRISB = %11111101 TRISC = %11111001 'PMW output for CCP1 AND CCP2 TRISA = %11111111 TMR2 = 0 PR2 = 199 'generate 5khz 'set for 18Khz HPWM CCP1CON = %00001100 'set CCP1 for PWM OPERATION CCP2CON = %00001100 'set CCP2 for PWM OPERATION T2CON = %00000100 'TIMER2ON and prescale of 1:1 sineval var byte[36] sineval[0] = 512 sineval[1] = 583 sineval[2] = 652 sineval[3] = 717 sineval[4] = 775 sineval[5] = 825 sineval[6] = 866 sineval[7] = 896 sineval[8] = 915 sineval[9] = 921 sineval[10] =915 sineval[11] =896 sineval[12] =866 sineval[13] =825 sineval[14] =775 sineval[15] =716 sineval[16] =652 sineval[17] =583 sineval[18] =512 sineval[19] = 441 sineval[20] = 372 sineval[21] = 308 sineval[22] = 249 sineval[23] = 199 sineval[24] = 158 sineval[25] = 128 sineval[26] = 109 sineval[27] = 103 sineval[28] = 109 sineval[29] = 128 sineval[30] = 158 sineval[31] = 199 sineval[32] = 249 sineval[33] = 308 sineval[34] = 372 sineval[35] = 441 timerone var word Temp var byte Temp1 var byte INCLUDE "DT_INTS-14.bas" ; Base Interrupt System emp 'INCLUDE "ReEnterPBP.bas" ASM INT_LIST macro ; IntSource, Label, Type, ResetFlag? INT_Handler TMR1_INT, _sine, ASM, yes endm INT_CREATE ; Creates the interrupt processor ENDASM T1CON = 000001 ; Prescaler = 1;1, TMR1 ON @ INT_ENABLE TMR1_INT ; Enable Timer 1 Interrupts timerone = 65080' gives1818hz nterruptfrequency or about 50 htz sine Main: PAUSE 1 GOTO Main '---[TMR1_INT - interrupt handler]------------------------------------------ sine: T1CON = 000000 'stop the timer TMR1L = timerone.byte0 'reload the timer TMR1H = timerone.byte1 T1CON = 000001 ' start the timer TeMP = sineval[STEPCOUNT] CCP1CON.4 = Temp.0 ' bit 0 CCP1CON.5 = Temp.1 ' bit 1 CCPR1L = Temp >>2 'Bit 2-7 TeMP1 = sineval[STEPCOUNT1] CCP2CON.4 = Temp1.0 ' bit 0 CCP2CON.5 = Temp1.1 ' bit 1 CCPR2L = Temp1 >>2 'Bit 2-7 TOGGLE LED1 stepcount = stepcount +1 stepcount1 = stepcount1 +1 if stepcount =36 then stepcount =0 if stepcount1 =36 then stepcount1 =0 @ INT_RETURN
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