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CCP PWM Strange behavior - Brief failing

 
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mellemhere



Joined: 14 Feb 2018
Posts: 4
Location: Brazil

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CCP PWM Strange behavior - Brief failing
PostPosted: Wed Feb 14, 2018 2:49 pm     Reply with quote

Hello all,

I am trying generate a PWM using CCP and change its frequency on the fly, going from 1.15KHz to 3.28kHz in 180ms.

I am using:

PIC: 16F887
Frequency: 4MHz (internal)
Compiler: CCS PCM C Compiler, Version 5.008


My problem is: My code is generating the PWM and going from 1.15KHz to 3.28kHz (50% duty) in 180ms as I wish to active, but it is also generating "holes", gaps, where nothing happens for some time.

This gaps goes from 3,7ms to 4,07ms, as shown by this image I could get from my oscilloscope:



I am doing this using the following code:

main.h
Code:

#include <16F887.h>
#device adc=8

#FUSES NOWDT                    //No Watch Dog Timer
#FUSES HS                       //High speed Osc (> 4mhz for PCM/PCH) (>10mhz for PCD)
#FUSES NOPUT                    //No Power Up Timer
#FUSES NOMCLR                   //Master Clear pin used for I/O
#FUSES NOPROTECT                //Code not protected from reading
#FUSES NOCPD                    //No EE protection
#FUSES NOBROWNOUT               //No brownout reset
#FUSES IESO                     //Internal External Switch Over mode enabled
#FUSES FCMEN                    //Fail-safe clock monitor enabled
#FUSES NOLVP                    //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NODEBUG                  //No Debug mode for ICD
#FUSES NOWRT                    //Program memory not write protected
#FUSES BORV40                   //Brownout reset at 4.0V
#FUSES RESERVED                 //Used to set the reserved FUSE bits

#use delay(clock=4000000)


main.c
Code:



/*
   Effect vars
*/
short STATE = 1;
int PR_VALUE = 33;
short CHANGED = 0;
int16 counter = 0;

#int_RDA
void  RDA_isr(void)
{
   //TO-DO   
}


/*
   Runs every 256us
*/
#int_RTCC
void  RTCC_isr(void)
{
   counter++;
}

/*
   Performs a step every 20x256us = 5.12ms
   Goes from 53 (1.15KHz) to 18 (3.28Khz)
*/
void EFFECT(){
   if(counter >= 20){
      CHANGED = 1;
      if(STATE){
         PR_VALUE++;
         if(PR_VALUE >= 53) STATE = 0;
      }else{
         PR_VALUE--;
         if(PR_VALUE <= 18) STATE = 1;
      }
     
      counter = 0;
   }
   
   if(CHANGED){
      CHANGED = 0;
   
      setup_timer_2(T2_DIV_BY_16, PR_VALUE, 1);
      set_pwm1_duty(PR_VALUE/2);
      set_pwm2_duty(PR_VALUE/2);
   }
}




void main()
{

   setup_comparator(NC_NC_NC_NC);
   setup_adc_ports(NO_ANALOGS|VSS_VDD);
   setup_adc(ADC_CLOCK_DIV_2);
   setup_spi(SPI_SS_DISABLED);
   
   setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
   
   setup_timer_1(T1_DISABLED); 
   
   setup_oscillator(OSC_4MHZ);
   
   enable_interrupts(INT_RTCC);
   
   enable_interrupts(INT_RDA);
   
   enable_interrupts(GLOBAL);
   
   setup_ccp1(CCP_PWM_L_H);
   setup_ccp2(CCP_PWM_H_L);
   
   while(1){
      EFFECT(); 
   }
}



Things I have done trying to fix this problem:

- Removed the counter and added a push button and for every push I incremented the PR value, I went from 18 1.15KHz to 3.28Khz without this "holes" appearing
- Attached an square wave frequency generator to the input where the push button was and noticed that the fasted I changed the PR more "holes" appeared


Any ideas how I am able to remove this weird errors?
temtronic



Joined: 01 Jul 2010
Posts: 6064
Location: Greensville,Ontario

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PostPosted: Wed Feb 14, 2018 3:12 pm     Reply with quote

OK, wild idea but.. change pr_value to an unsigned 16 bit and use 33L not 33.
The timer register is 16 bit so the upper byte might be anything. The 33L forces 33 to be 16 bits.not just 8 bits, so it'll properly set the register.

I'm not sure if this will work, but it has been seen in the past. A dump of the listing would show if the compiler is setting BOTH high and low bytes or just the low byte.

If nothing else it's easy to try and if it works, great if not, well...we've eliminated that possiblity.

Jay
mellemhere



Joined: 14 Feb 2018
Posts: 4
Location: Brazil

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PostPosted: Wed Feb 14, 2018 3:27 pm     Reply with quote

Hi Jay! Thanks for the reply

I have performed the changes you sugested, changed the pr_value to an unsigned int16 and added the L after the 33. As you can see this is my code right now:

Code:


short STATE = 1;
unsigned int16 PR_VALUE = 33L;
short CHANGED = 0;
int16 counter = 0;


The rest of the code is unchanged.

Running this code I still have those "holes" and for some reason my duty cycle is not 50% anymore, but it doesn't matter much.

This is what I see now:


Sorry if it is a noob question, but how can I get the dump of the listing?

Thanks for replying!

*Edit: Changing unsigned int16 PR_VALUE = 33L; to unsigned int PR_VALUE = 33L; brought back the 50% duty but still have those "holes"
temtronic



Joined: 01 Jul 2010
Posts: 6064
Location: Greensville,Ontario

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PostPosted: Wed Feb 14, 2018 3:34 pm     Reply with quote

list is

project's filename.lst

so whatever you named the project or source with a dotLST after it.

If using MPLAB, you can see it by selecting 'view', then select 'disassembly listing'.

Jay
mellemhere



Joined: 14 Feb 2018
Posts: 4
Location: Brazil

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PostPosted: Wed Feb 14, 2018 3:36 pm     Reply with quote

This is my listing:

Code:

CCS PCM C Compiler, Version 5.008, 5967               14-fev-18 19:28

               Filename:  main.lst

               ROM used:   234 words (3%)
                           Largest free fragment is 2048
               RAM used:   17 (5%) at main() level
                           18 (5%) worst case
               Stack used: 2 locations (1 in main + 1 for interrupts)
               Stack size: 8

*
0000:  MOVLW  00
0001:  MOVWF  0A
0002:  GOTO   070
0003:  NOP
0004:  MOVWF  7F
0005:  SWAPF  03,W
0006:  CLRF   03
0007:  MOVWF  21
0008:  MOVF   0A,W
0009:  MOVWF  20
000A:  CLRF   0A
000B:  MOVF   04,W
000C:  MOVWF  22
000D:  MOVF   77,W
000E:  MOVWF  23
000F:  MOVF   78,W
0010:  MOVWF  24
0011:  MOVF   79,W
0012:  MOVWF  25
0013:  MOVF   7A,W
0014:  MOVWF  26
0015:  BCF    03.7
0016:  BCF    03.5
0017:  BTFSS  0B.5
0018:  GOTO   01B
0019:  BTFSC  0B.2
001A:  GOTO   032
001B:  MOVLW  8C
001C:  MOVWF  04
001D:  BTFSS  00.5
001E:  GOTO   021
001F:  BTFSC  0C.5
0020:  GOTO   035
0021:  MOVF   22,W
0022:  MOVWF  04
0023:  MOVF   23,W
0024:  MOVWF  77
0025:  MOVF   24,W
0026:  MOVWF  78
0027:  MOVF   25,W
0028:  MOVWF  79
0029:  MOVF   26,W
002A:  MOVWF  7A
002B:  MOVF   20,W
002C:  MOVWF  0A
002D:  SWAPF  21,W
002E:  MOVWF  03
002F:  SWAPF  7F,F
0030:  SWAPF  7F,W
0031:  RETFIE
0032:  BCF    0A.3
0033:  BCF    0A.4
0034:  GOTO   03C
0035:  BCF    0A.3
0036:  BCF    0A.4
0037:  GOTO   038
.................... #include "main.h"
.................... #include <16F887.h>
.................... //////// Standard Header file for the PIC16F887 device ////////////////
.................... #device PIC16F887
.................... 
.................... #list
.................... 
.................... #device adc=8
.................... 
.................... #FUSES NOWDT                    //No Watch Dog Timer
.................... #FUSES HS                       //High speed Osc (> 4mhz for PCM/PCH) (>10mhz for PCD)
.................... #FUSES NOPUT                    //No Power Up Timer
.................... #FUSES NOMCLR                   //Master Clear pin used for I/O
.................... #FUSES NOPROTECT                //Code not protected from reading
.................... #FUSES NOCPD                    //No EE protection
.................... #FUSES NOBROWNOUT               //No brownout reset
.................... #FUSES IESO                     //Internal External Switch Over mode enabled
.................... #FUSES FCMEN                    //Fail-safe clock monitor enabled
.................... #FUSES NOLVP                    //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
.................... #FUSES NODEBUG                  //No Debug mode for ICD
.................... #FUSES NOWRT                    //Program memory not write protected
.................... #FUSES BORV40                   //Brownout reset at 4.0V
.................... #FUSES RESERVED                 //Used to set the reserved FUSE bits
.................... 
.................... #use delay(clock=4000000)
.................... #use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)
.................... 
.................... 
.................... 
.................... 
.................... 
.................... /*
....................    Effect vars
.................... */
.................... short STATE = 1;
.................... unsigned int PR_VALUE = 33L;
.................... short CHANGED = 0;
.................... int16 counter = 0;
.................... 
.................... #int_RDA
.................... void  RDA_isr(void) 
.................... {
....................    //p_charRecived();     
.................... }
.................... 
.................... 
.................... /*
....................    Runs every 256us
.................... */
0038:  BCF    0C.5
0039:  BCF    0A.3
003A:  BCF    0A.4
003B:  GOTO   021
.................... #int_RTCC
.................... void  RTCC_isr(void) 
.................... {
....................    counter++;
003C:  INCF   29,F
003D:  BTFSC  03.2
003E:  INCF   2A,F
003F:  BCF    0B.2
0040:  BCF    0A.3
0041:  BCF    0A.4
0042:  GOTO   021
.................... }
.................... 
.................... /*
....................    Performs a step every 20x256us = 5.12ms
....................    Goes from 53 (1.15KHz) to 18 (3.28Khz)
.................... */
.................... void EFFECT(){
....................    if(counter >= 20){
0043:  MOVF   2A,F
0044:  BTFSS  03.2
0045:  GOTO   04A
0046:  MOVF   29,W
0047:  SUBLW  13
0048:  BTFSC  03.0
0049:  GOTO   05A
....................       CHANGED = 1;
004A:  BSF    27.1
....................       if(STATE){
004B:  BTFSS  27.0
004C:  GOTO   053
....................          PR_VALUE++;
004D:  INCF   28,F
....................          if(PR_VALUE >= 53) STATE = 0;
004E:  MOVF   28,W
004F:  SUBLW  34
0050:  BTFSS  03.0
0051:  BCF    27.0
....................       }else{
0052:  GOTO   058
....................          PR_VALUE--;
0053:  DECF   28,F
....................          if(PR_VALUE <= 18) STATE = 1;
0054:  MOVF   28,W
0055:  SUBLW  12
0056:  BTFSC  03.0
0057:  BSF    27.0
....................       }
....................       
....................       counter = 0;
0058:  CLRF   2A
0059:  CLRF   29
....................    }
....................     
....................    if(CHANGED){
005A:  BTFSS  27.1
005B:  GOTO   06D
....................       CHANGED = 0;
005C:  BCF    27.1
....................     
....................       setup_timer_2(T2_DIV_BY_16, PR_VALUE, 1);
005D:  MOVLW  00
005E:  MOVWF  78
005F:  IORLW  06
0060:  MOVWF  12
0061:  MOVF   28,W
0062:  BSF    03.5
0063:  MOVWF  12
....................       set_pwm1_duty(PR_VALUE/2);
0064:  BCF    03.0
0065:  BCF    03.5
0066:  RRF    28,W
0067:  MOVWF  2C
0068:  MOVWF  15
....................       set_pwm2_duty(PR_VALUE/2);
0069:  BCF    03.0
006A:  RRF    28,W
006B:  MOVWF  2C
006C:  MOVWF  1B
....................    }
006D:  BCF    0A.3
006E:  BCF    0A.4
006F:  GOTO   0E8 (RETURN)
.................... }
.................... 
.................... 
.................... 
.................... 
.................... void main()
0070:  MOVF   03,W
0071:  ANDLW  1F
0072:  MOVWF  03
0073:  BSF    03.5
0074:  BSF    03.6
0075:  BCF    07.3
0076:  MOVLW  19
0077:  BCF    03.6
0078:  MOVWF  19
0079:  MOVLW  A6
007A:  MOVWF  18
007B:  MOVLW  90
007C:  BCF    03.5
007D:  MOVWF  18
007E:  BSF    27.0
007F:  MOVLW  21
0080:  MOVWF  28
0081:  BCF    27.1
0082:  CLRF   2A
0083:  CLRF   29
0084:  MOVLW  FF
0085:  MOVWF  2B
0086:  BSF    03.5
0087:  BSF    03.6
0088:  MOVF   09,W
0089:  ANDLW  C0
008A:  MOVWF  09
008B:  BCF    03.6
008C:  BCF    1F.4
008D:  BCF    1F.5
008E:  MOVLW  00
008F:  BSF    03.6
0090:  MOVWF  08
0091:  BCF    03.5
0092:  CLRF   07
0093:  CLRF   08
0094:  CLRF   09
0095:  BCF    03.7
.................... {
.................... 
....................    setup_comparator(NC_NC_NC_NC);
0096:  CLRF   07
0097:  CLRF   08
0098:  CLRF   09
....................    setup_adc_ports(NO_ANALOGS|VSS_VDD);
0099:  BSF    03.5
009A:  MOVF   09,W
009B:  ANDLW  C0
009C:  MOVWF  09
009D:  BCF    03.6
009E:  BCF    1F.4
009F:  BCF    1F.5
00A0:  MOVLW  00
00A1:  BSF    03.6
00A2:  MOVWF  08
....................    setup_adc(ADC_CLOCK_DIV_2);
00A3:  BCF    03.5
00A4:  BCF    03.6
00A5:  BCF    1F.6
00A6:  BCF    1F.7
00A7:  BSF    03.5
00A8:  BCF    1F.7
00A9:  BCF    03.5
00AA:  BSF    1F.0
....................    setup_spi(SPI_SS_DISABLED);
00AB:  BCF    14.5
00AC:  BCF    2B.5
00AD:  MOVF   2B,W
00AE:  BSF    03.5
00AF:  MOVWF  07
00B0:  BCF    03.5
00B1:  BSF    2B.4
00B2:  MOVF   2B,W
00B3:  BSF    03.5
00B4:  MOVWF  07
00B5:  BCF    03.5
00B6:  BCF    2B.3
00B7:  MOVF   2B,W
00B8:  BSF    03.5
00B9:  MOVWF  07
00BA:  MOVLW  01
00BB:  BCF    03.5
00BC:  MOVWF  14
00BD:  MOVLW  00
00BE:  BSF    03.5
00BF:  MOVWF  14
....................     
....................    setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
00C0:  MOVF   01,W
00C1:  ANDLW  C7
00C2:  IORLW  08
00C3:  MOVWF  01
....................     
....................    setup_timer_1(T1_DISABLED);   
00C4:  BCF    03.5
00C5:  CLRF   10
....................     
....................    setup_oscillator(OSC_4MHZ);
00C6:  MOVLW  61
00C7:  BSF    03.5
00C8:  MOVWF  0F
00C9:  MOVF   0F,W
....................     
....................    enable_interrupts(INT_RTCC);
00CA:  BCF    03.5
00CB:  BSF    0B.5
....................     
....................    enable_interrupts(INT_RDA);
00CC:  BSF    03.5
00CD:  BSF    0C.5
....................     
....................    enable_interrupts(GLOBAL);
00CE:  MOVLW  C0
00CF:  BCF    03.5
00D0:  IORWF  0B,F
....................     
....................    setup_ccp1(CCP_PWM_L_H);
00D1:  BCF    2B.2
00D2:  MOVF   2B,W
00D3:  BSF    03.5
00D4:  MOVWF  07
00D5:  BCF    03.5
00D6:  BCF    07.2
00D7:  MOVLW  0E
00D8:  MOVWF  17
00D9:  BSF    03.5
00DA:  CLRF   1B
00DB:  CLRF   1C
00DC:  MOVLW  01
00DD:  MOVWF  1D
....................    setup_ccp2(CCP_PWM_H_L);
00DE:  BCF    03.5
00DF:  BCF    2B.1
00E0:  MOVF   2B,W
00E1:  BSF    03.5
00E2:  MOVWF  07
00E3:  BCF    03.5
00E4:  BCF    07.1
00E5:  MOVLW  0D
00E6:  MOVWF  1D
....................     
....................    while(1){
....................       EFFECT();   
00E7:  GOTO   043
00E8:  GOTO   0E7
....................    }
.................... }
.................... 
00E9:  SLEEP

Configuration Fuses:
   Word  1: 2CD2   HS NOWDT NOPUT NOMCLR NOPROTECT NOCPD NOBROWNOUT IESO FCMEN NOLVP NODEBUG
   Word  2: 3FFF   BORV40 NOWRT
temtronic



Joined: 01 Jul 2010
Posts: 6064
Location: Greensville,Ontario

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PostPosted: Wed Feb 14, 2018 7:21 pm     Reply with quote

OK, I was wrong...timer 2 for the 16F887 is ONLY 8 bits...for some reason I thought it was 16 bits...arrgh.. too many PICs ..
The listing does show an important detail though. The compiler you're using is 5.008. very very 'young'. Hopefully someone can test on their system, me, well, 'somehow' Windows just lost 24,000+ PIC files while I was out, so I have a huge nightmare to deal with once the sun comes up.
Jay
Ttelmah



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Posts: 13042

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PostPosted: Thu Feb 15, 2018 2:40 am     Reply with quote

I've input a modified version, with several comments 'inline'.
See if this improves on things.
Code:

#include <16F887.h>
#device adc=8

#FUSES NOWDT                    //No Watch Dog Timer
#FUSES HS                       //High speed Osc (> 4mhz for PCM/PCH) (>10mhz for PCD)
#FUSES NOPUT                    //No Power Up Timer
#FUSES NOMCLR                   //Master Clear pin used for I/O
#FUSES NOPROTECT                //Code not protected from reading
#FUSES NOCPD                    //No EE protection
#FUSES NOBROWNOUT               //No brownout reset
#FUSES IESO                     //Internal External Switch Over mode enabled
#FUSES FCMEN                    //Fail-safe clock monitor enabled
#FUSES NOLVP                    //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NODEBUG                  //No Debug mode for ICD
#FUSES NOWRT                    //Program memory not write protected
#FUSES BORV40                   //Brownout reset at 4.0V
#FUSES RESERVED                 //Used to set the reserved FUSE bits

#use delay(clock=4000000)

#define UP TRUE
#define DOWN FALSE
/*
   Effect vars
*/
short State = UP;   //start counting up
int8 Pr_Value = 33;
int8 counter = 0;
//As a general comment, it is a standard in C, to reserve ALLCAPITALS
//for #defines, and ENUM values. Helps to give an immediate 'hint' as to what
//a value actually 'is'. Have changed the variable names here to this form.

/*
   Runs every 1024us
*/
#int_RTCC
void  RTCC_isr(void)
{
   counter++;
}

/*
   Performs a step every 5*1024us = 5.12ms
   Goes from 53 (1.15KHz) to 18 (3.28Khz)
*/
void Effect(void)
{
   if(counter >= 5)
   {
      counter = 0;     
      if(State==UP)
      {
         Pr_Value++;
         if(Pr_Value >= 53)
            State = DOWN;
      }
      else
      {
         Pr_Value--;
         if(Pr_Value <= 18)
            State = UP;
      }   
      //Here it has changed. Why test again?....   
      clear_interrupt(INT_TIMER2); //wait for Timer2 to update
      while (!interrupt_active(INT_TIMER2))
          ;
      //now reprogram the timer only in the moment after a cycle finishes
      setup_timer_2(T2_DIV_BY_16, PR_VALUE, 1);
      set_pwm1_duty(((int16)PR_VALUE)*2);
      set_pwm2_duty(((int16)PR_VALUE)*2);
   }
}

void main()
{
   setup_oscillator(OSC_4MHZ);
 
   setup_comparator(NC_NC_NC_NC);
   setup_adc_ports(NO_ANALOGS|VSS_VDD);
   setup_adc(ADC_CLOCK_DIV_8);
   //DIV_2 is too fast. At 4MHz DIV_8 is needed
   setup_spi(FALSE);
   //correct command to disable SPI
   
   setup_timer_0(RTCC_INTERNAL|T0_DIV_4);
   //Slight problem here. DIV_1 means this interrupt will be triggering every 256
   //instructions. *4 takes this to 1024. At 256 instructions, about 1/4 of your
   //entire processor time will be used to just handle the counter....
   
   setup_timer_1(T1_DISABLED);
     
   enable_interrupts(INT_RTCC);
   
   //enable_interrupts(INT_RDA); //Don't enable this till you have a handler
   //That actually reads the character. Otherwise chip will be hung.
   
   enable_interrupts(GLOBAL);
   
   setup_ccp1(CCP_PWM_L_H);
   setup_ccp2(CCP_PWM_H_L);
   
   while(TRUE)
   {
      Effect();
   }
}


The change affecting what you are seeing, is I now update the PWM, only immediately after the PWM timer resets. This avoids a problem if the timer has already _passed_ the PR2 value when you set it to a lower value.

So (for instance), imagine the timer is at 49, and you set PR2 to 49. The set takes effect on the next cycle, so PR2 is set to 49, and the timer is now at 50. At this point it'll count up to 255, reset, and then count up to 49, and so you get a 'long' cycle about 6* the value it ought to have....
mellemhere



Joined: 14 Feb 2018
Posts: 4
Location: Brazil

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PostPosted: Thu Feb 15, 2018 7:27 am     Reply with quote

Hi! Thank you so much for the reply.

I ran your code and got no output. After a little bit of debugging I found out that the following two lines were the cause of this.

Code:

      //Here it has changed. Why test again?....   
      clear_interrupt(INT_TIMER2); //wait for Timer2 to update
      while (!interrupt_active(INT_TIMER2));


If I have this two lines in the code nothing happens (no output), if I remove them I have an output but with those "holes". What could it be?

Another way I tried to sove this was by adding the following statement to my code:

Code:

         if(get_timer2() > PR_VALUE){
            set_timer2(PR_VALUE);
         }


Making my Effect function look like this:

Code:

   if(counter >= 5){
      CHANGED = 1;
      if(!state){
         PR_VALUE++;
         if(PR_VALUE >= 53) STATE = 1;
      }else{
         PR_VALUE--;
         if(PR_VALUE <= 18) STATE = 0;
      }
     
      counter = 0;
   }
   
   if(CHANGED){
      CHANGED = 0;
         if(get_timer2() > PR_VALUE){
            set_timer2(PR_VALUE);
         }
      setup_timer_2(T2_DIV_BY_16, PR_VALUE, 1);
      set_pwm1_duty(PR_VALUE/2);
      set_pwm2_duty(PR_VALUE/2);
   }


It made the holes appear much less frequently, but I can still see some once or twice in the oscilloscope.

Thank you so much for the help! Hope we can find out why those two lines of your code are blocking the flow, because your code is much better than mine.
Ttelmah



Joined: 11 Mar 2010
Posts: 13042

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PostPosted: Thu Feb 15, 2018 9:30 am     Reply with quote

OK. That almost certainly means your compiler version has a fault in the handling of this bit. It is a very early version.
You can program round with:
Code:

#byte PIR1 = 0xC //given the age I'm not trusting getenv
#bit TMR2IF = PIR1.1

//Then use
    TMR2IF=FALSE;
    while (TMR2IF==FALSE)
        ;


You are still adding the extra test for changed. Pointless.
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