ProblemwithPWMfrequency

[Demon]

He checks for 36, shouldn't it be 35?

Robert

[ScaleRobotics]

He checks for 36, shouldn't it be 35?

No, after completing step 35, it increments, then it does a = 36 check. If it = 36, it goes back to step 0.

[Demon]

Right, I forgot to check when the step was incremented, argh, and that's basic debugging procedure too (must be going senile).

[Demon]

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

[sangaboy]

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 ).

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

[Acetronics2]

Hi,

Do not trust in Proteus/Isis ...

I sometimes have some VERY funny results when it perfectly works in real life ...

" lots of examples available " ... especially when schemes are mixing analogic and digital !!!

Alain

[Darrel Taylor]

sineval var byte[36]
sineval[0] = 512    
sineval[1] = 583
...

The array should be of WORDs if you want it to hold values greater than 255.

PROTEUS Rules!!

[HenrikOlsson]

What Darrel said.

AND

In a post made March 13th:

You answered your own question in (1) from the Midrange manual:

(1) " If the PWM duty cycle value is longer than the PWM period, the CCPx pin will not be cleared. This allows a duty cycle of 100%".

Any dutycycle value above 796 will result in 100% dutycycle. In other words your SIN-output will be distorted/clipped.

You have several values larger than 796 (4*199 (which is what you have PR2 set to, remember we've been thru this)) in your lookuptable so you are "overdriving" the dutycycle register and "clipping" will occur.

/Henrik.

[sangaboy]

Hi to all
I tried to modify the code according to Darrel Taylor and HenrikOlsson comments but the problem still exits, let me put in real hardware and see what happen.
And here is modified code but the output is still like that posted in the previous post.

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 word[36]
sineval[0] = 512    
sineval[1] = 556   
sineval[2] = 599
sineval[3] = 640
sineval[4] = 676
sineval[5] = 707
sineval[6] = 733
sineval[7] = 752
sineval[8] = 763
sineval[9] = 767  
sineval[10] =763
sineval[11] =752
sineval[12] =733   
sineval[13] =707
sineval[14] =676
sineval[15] =640
sineval[16] =599
sineval[17] =556
sineval[18] =512   
sineval[19] =468
sineval[20] =425
sineval[21] =385 
sineval[22] =348
sineval[23] =317
sineval[24] =291
sineval[25] =272
sineval[26] =261
sineval[27] =257
sineval[28] =261 
sineval[29] =272
sineval[30] = 291
sineval[31] = 317
sineval[32] = 348
sineval[33] = 385
sineval[34] = 425
sineval[35] = 468

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,   PBP,  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

Thanks.