Changing the sines frequency?

[pxidr84]

Hi everyone,

I'm again here with my three-phase sines.

All works great, I can change the frequency (by varying the interrupt "timer" variable) and the amplitude of my sines (by varying the "amplitude" variable).

But something is strange with the timer : the output sines frequency is not proportinal with the timer value. There is what I get from real experimentations :


Of course, for the calculation of U/F variables, is far more complicated.

So, how I can calculate the output frequency of my sines internally by the PIC?
Or how I can change the sines frequency proportionally with an another method than varying "timer" variable?

Thanks.

Code :

' PIC initialization
DEFINE OSC 40      
DEFINE LCD_DREG PORTC
DEFINE LCD_EREG PORTD
DEFINE LCD_RSREG PORTD
DEFINE LCD_EBIT 0
DEFINE LCD_RSBIT 1
DEFINE LCD_COMMANDUS 4000
DEFINE LCD_DATAUS 100
DEFINE USE_LOWPRIORITY 1


' BAS includes
INCLUDE "DT_INTS-18.bas"
INCLUDE "ReEnterPBP-18.bas"
INCLUDE "ReEnterPBP-18LP.bas"
INCLUDE "Sine_table.bas"
INCLUDE "Freq_table.bas"


' Port registers configuration
TRISB=%11000000   ' PWM 0,1,2,3,4,5 outputs
TRISC=%00110000   ' +/- buttons


' PCPWM registers configuration
DTCON=%110        ' Deadtime (600ns)
PTCON0=%0         ' 1:1 postscale, Fosc/4 1:1 prescale, free running mode
PTCON1=%10000000  ' PWM time base is ON, counts up, 19.45kHz/4
PWMCON0=%1000000  ' PWM 0,1,2,3,4,5 set in pair mode
PWMCON1=%1        ' PWM timer sync configuration


' PWM calculation variables
ustep var byte
vstep var byte
wstep var byte
uduty var word
vduty var word
wduty var word
timer var word
amplitude var word
carrier VAR word
flag var bit


' Variables definition
ustep=72          ' 360 degrees phase angle
vstep=48          ' 240 degrees phase angle
wstep=24          ' 120 degrees phase angle
timer=64120       ' Timer adjust (64120=120Hz) 
amplitude=65535   ' Sinewave amplitude adjust (65535=max amplitude)
carrier=1023      ' Carrier frequency adjust (1023=13kHz)
flag=%0           ' Menu flag


' PWM carrier frequency register configuration
PTPERL=carrier.lowbyte  
PTPERH=carrier.highbyte

  
' Interrupt processors 
ASM
INT_LIST macro
         INT_Handler TMR1_INT,_pwmint,PBP,yes
         endm
         INT_CREATE 
    
INT_LIST_L macro
           INT_Handler TMR0_INT,_mainint,PBP,no
           endm
           INT_CREATE_L       
ENDASM

    
' Timers configuration
T1CON=%10000001
T0CON=%10000111


' Interrupts enable
@ INT_ENABLE TMR1_INT
@ INT_ENABLE TMR0_INT


' PWM calculation and update interrupt (Timer 1) 
pwmint:

' Timer 1 update
TMR1L=timer.lowbyte
TMR1H=timer.highbyte

' PWM U phase calculation
uduty=sine[ustep]
uduty=uduty<<4**amplitude+3

' PWM V phase calculation
vduty=sine[vstep]
vduty=vduty<<4**amplitude+3

' PWM W phase calculation
wduty=sine[wstep]
wduty=wduty<<4**amplitude+3

' PWM U, V and W update
PDC0L=uduty.lowbyte
PDC0H=uduty.highbyte
PDC1L=vduty.lowbyte
PDC1H=vduty.highbyte
PDC2L=wduty.lowbyte
PDC2H=wduty.highbyte

' Phase angle calculation
ustep=ustep-1
vstep=vstep-1
wstep=wstep-1

' Phase angle reinitialization
if ustep=0 then ustep=72
if vstep=0 then vstep=72
if wstep=0 then wstep=72

@ INT_RETURN


' Main program loop interrupt (Timer 0)
mainint:

' Debug display
if flag=0 then
LCDOUT $FE,$2,"Timer adjust :"
LCDOUT $FE,$C0,DEC5 timer
if PORTC.4=1 then timer=timer-1
if PORTC.5=1 then timer=timer+1
IF PORTC.4 AND PORTC.5=1 then flag=%1
else
LCDOUT $FE,$2,"Amp. adjust :"
LCDOUT $FE,$C0,DEC5 amplitude
if PORTC.4=1 then amplitude=amplitude-1
if PORTC.5=1 then amplitude=amplitude+1
endif

@ INT_RETURN

[HenrikOlsson]

Hi,
Running the PIC at 40Mhz and having a prescaler on TMR1 of 1:1 (no prescaler) makes it "tick" at 10MHz. Your sine-table, if I understand correctly contains 72 "steps" so you need 72 interrupts per second per Hz output frequency.

At 120 Hz output frequency you need 120*72= 8640Hz or an interrupt interval of 115.7us. At 10Mhz one "tick" is 0.1us so you need 1116 ticks between interrupts and therefor you should (theoretically) reload the timer with: 65536-1116 = 64420.

At 10Hz you need 720 interrupts per second or an interrupt interval of 1388.9us. That's 13889 ticks so you need to reload the timer with 65536-13889 = 51647.


Now, when the timer overflows and trips the interrupt a lot of things has to happend. The DT-Ints interrupt "engine" has to save all the PBP system varibles and this takes time. By the time the code actually gets to reloading TMR1 with your calculated reload value several hundred cycles have passed. If you then reload it with the "original", calculated value you are effectively "turning back the time" or reclaiming time that has already passed.

What you usually do is stop the timer, make a copy of its content and then ADD the reload value to the value of the copy. Then you put the value back in the timer and restart it. Obviously this too takes a couple of cycles so to be really accurate you need to tweak the reload values to account for it. Basically

TimerShadow VAR WORD
 
T1CON.0 = 0  'Stop TMR1
TimerShadow.HighByte = TMR1H
TimerShadow.LowByte = TMR1L
TimerShadow = TimerShadow + TimerReload
TMR1H = TimerShadow.HighByte
TMR1L = TimerShadow.LowByte
T1CON.0 = 1  'Restart TMR1

I see that you have 16bit read/write of TMR1 enabled, I don't know how that affects the above but I'd probably turn that off to begin with.

In the INT_List for the low priority interrupt you have the Reset_Flag set to NO for TMR0 - why is that? You don't seem to reset it "manually" in the ISR.

Finally, in your TMR0 interupt, don't do the LCDOUT etc in there. Set a flag and get out of there, then in your main routine you check the flag, if set do whatever and reset the flag.

[pxidr84]

Thanks Henrik (again), I will make some experiments with your tips.

[pxidr84]

Hi,
Running the PIC at 40Mhz and having a prescaler on TMR1 of 1:1 (no prescaler) makes it "tick" at 10MHz. Your sine-table, if I understand correctly contains 72 "steps" so you need 72 interrupts per second per Hz output frequency.

At 120 Hz output frequency you need 120*72= 8640Hz or an interrupt interval of 115.7us. At 10Mhz one "tick" is 0.1us so you need 1116 ticks between interrupts and therefor you should (theoretically) reload the timer with: 65536-1116 = 64420.

At 10Hz you need 720 interrupts per second or an interrupt interval of 1388.9us. That's 13889 ticks so you need to reload the timer with 65536-13889 = 51647.


Now, when the timer overflows and trips the interrupt a lot of things has to happend. The DT-Ints interrupt "engine" has to save all the PBP system varibles and this takes time. By the time the code actually gets to reloading TMR1 with your calculated reload value several hundred cycles have passed. If you then reload it with the "original", calculated value you are effectively "turning back the time" or reclaiming time that has already passed.

What you usually do is stop the timer, make a copy of its content and then ADD the reload value to the value of the copy. Then you put the value back in the timer and restart it. Obviously this too takes a couple of cycles so to be really accurate you need to tweak the reload values to account for it. Basically

TimerShadow VAR WORD
 
T1CON.0 = 0  'Stop TMR1
TimerShadow.HighByte = TMR1H
TimerShadow.LowByte = TMR1L
TimerShadow = TimerShadow + TimerReload
TMR1H = TimerShadow.HighByte
TMR1L = TimerShadow.LowByte
T1CON.0 = 1  'Restart TMR1

I see that you have 16bit read/write of TMR1 enabled, I don't know how that affects the above but I'd probably turn that off to begin with.

In the INT_List for the low priority interrupt you have the Reset_Flag set to NO for TMR0 - why is that? You don't seem to reset it "manually" in the ISR.

Finally, in your TMR0 interupt, don't do the LCDOUT etc in there. Set a flag and get out of there, then in your main routine you check the flag, if set do whatever and reset the flag.

Excuse me for my misunderstanding...
I've made some experiments with your routine, I can change the frequency, but even not proportionnaly, how do you integrate your routine into my program?

[HenrikOlsson]

Hi,
It's possible that you are simply trying to interrupt to fast and that it's overrunning it self - ie, another interrupt occurs before while servicing the first one. Try removing the all code from your ISR and replace with a simple TOGGLE PORTB.0 or whatever, measure the frequency of the output, that should give a clue as to what is going on.

[pxidr84]

Now I use this DT routine -> http://darreltaylor.com/DT_INTS-14/TimerTemplate.html

Hurray, I can set my desired interrupt frequency, so I can get my desired output frequency. It's the same principle of your code above.

But I've a little problem :

I like to define this ASM variable (@Freq = 10 ) to a PBP variable (for modify it in PBP and display it on the LCD for example).

I've tried this :
intfreq VAR WORD
intfreq=5000
@Freq = _intfreq

But it doesn't work at all.

Here's the DT timer template code :

; Initialize your hardware first

DEFINE OSC 20

INCLUDE "DT_INTS-14.bas"     ; Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ; Include if using PBP interrupts

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,   ReloadTMR1,   ASM,  no    ; MUST be first
        INT_Handler   TMR1_INT,   _T1handler,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

;--- Change these to match the desired interrupt frequency -------------------
;--- See http://DarrelTaylor.com/DT_INTS-14/TimerTemplate.html for more Info.
@Freq       = 10                  ; Frequency of Interrupts in Hz
@Prescaler  = 8                   ; Timers Prescaler setting
T1CON = $30                       ; $30 = Prescaler 1:8, TMR1 OFF
; $00=1:1, $10=1:2, $20=1:4, $30=1:8 --  Must match @Prescaler value

@ INT_ENABLE  TMR1_INT            ; enable Timer 1 interrupts
GOSUB StartTimer                  ; Start the Timer

;____Your Main Program goes here______________________________________________
Main:
  ;   ---- Your Main Program goes here ----
GOTO Main

;____This routine is Called on each TMR1 Interrupt____________________________
T1handler:
  ;   ---- Your interrupt routine goes here ----
  
@ INT_RETURN

;---[TMR1 reload - interrupt handler]-----------------------------------------
ASM                               ; Calculate Timer Reload Constant
ReloadInst  = 8                   ; # of Intructions used to reload timer
  if ((Prescaler == 1)||(Prescaler == 2)||(Prescaler == 4)||(Prescaler == 8))
MaxCount    = 65536 + (ReloadInst / Prescaler)
TimerReload = MaxCount - (OSC*1000000/4/Prescaler/Freq)
    if ((TimerReload < 0) || (TimerReload > (65535-ReloadInst)))
        error Invalid Timer Values - check "OSC", "Freq" and "Prescaler"
    endif
  else
      error Invalid Prescaler
  endif
ENDASM

@Timer1 = TMR1L                   ; map timer registers to a word variable
Timer1       VAR WORD EXT
TimerReload  CON EXT              ; Get the External Constant
TMR1ON       VAR T1CON.0          ; Alias the Timers ON/OFF bit

;---Reload Timer1------
ASM
ReloadTMR1
    MOVE?CT  0, T1CON, TMR1ON     ;  1     stop timer
    MOVLW    LOW(TimerReload)     ;  1     Add TimerReload to the 
    ADDWF    TMR1L,F              ;  1     value in Timer1
    BTFSC    STATUS,C             ;  1/2
    INCF     TMR1H,F              ;  1
    MOVLW    HIGH(TimerReload)    ;  1
    ADDWF    TMR1H,F              ;  1
    MOVE?CT  1, T1CON, TMR1ON     ;  1     start timer
  INT_RETURN
ENDASM

;---Start/Stop controls -----
StartTimer:
    Timer1  = TimerReload         ; Load Timer
    TMR1ON = 1                    ; start timer
RETURN

StopTimer:
    TMR1ON = 0                    ; stop timer
RETURN

[HenrikOlsson]

Hi
Aren't you using a PIC18F4431? If so you should use DT-INTS-18 but I suspect that is what you are doing even if you posted the DT-INTS-14 code?

Right, as far as I know the Freq variable isn't a variable it's an assembler constant. The TimerReload value is calculated at assembly time (not runtime) so once the code is assembled Freq no longer exists and can't be changed.

If you're using the timer template then it's the TimerReload value you should change in order to change the frequency - which is the same thing as we've been thru earlier in the thread.

/Henrik.

[pxidr84]

Of course I'm using DT-INTS_18. Above is the sample code provided by Darrel.

I've misreaded this line : "The frequency will remain constant and cannot be changed during Run-Time." F*ck.

You tell me to stop the timer, make a copy, and restart it. Only the "Timer1" variable can be changed in this DT's routine. Some routines are already made on this program : "StartTimer" and "StopTimer".

I'm sorry, but I'd like you modify my program, because I'm completly stuck at this point so many days...

The only thing I want is control the TMR1 interrupt frequency precisely, even in runtime.

I've tried

TimerShadow VAR WORD
TimerShadow=5000

.
.
.

StartTimer:
Timer1=TimerReload+TimerShadow         
TMR1ON=1                    
RETURN

But of course it didn't works.

I've also modified the code assuming your tips :

' PIC initialization
DEFINE OSC 40      
DEFINE LCD_DREG PORTC
DEFINE LCD_EREG PORTD
DEFINE LCD_RSREG PORTD
DEFINE LCD_EBIT 0
DEFINE LCD_RSBIT 1
DEFINE LCD_COMMANDUS 4000
DEFINE LCD_DATAUS 1000


' BAS includes
INCLUDE "DT_INTS-18.bas"
INCLUDE "ReEnterPBP-18.bas"
INCLUDE "Sine_table.bas"


' Port registers configuration
TRISB=%11000000   ' PWM 0,1,2,3,4,5 outputs
TRISC=%00110000   ' +/- buttons


' PCPWM registers configuration
DTCON=%110        ' Deadtime (600ns)
PTCON0=%0         ' 1:1 postscale, Fosc/4 1:1 prescale, free running mode
PTCON1=%10000000  ' PWM time base is ON, counts up, 19.45kHz/4
PWMCON0=%1000000  ' PWM 0,1,2,3,4,5 set in pair mode
PWMCON1=%1        ' PWM timer sync configuration


' PWM calculation variables
ustep var byte
vstep var byte
wstep var byte
uduty var word
vduty var word
wduty var word
frequency var word
amplitude var word
carrier VAR word
flag var bit


' Variables definition
ustep=90          ' 360 degrees phase angle
vstep=60          ' 240 degrees phase angle
wstep=30          ' 120 degrees phase angle
frequency=1200    ' Frequency adjust
amplitude=65535   ' Sinewave amplitude adjust (65535=max amplitude)
carrier=1023      ' Carrier frequency adjust (1023=13kHz)
flag=%0           ' Menu flag


' PWM carrier frequency register configuration
PTPERL=carrier.lowbyte  
PTPERH=carrier.highbyte

  
' Interrupt processors 
ASM
INT_LIST macro
INT_Handler TMR1_INT,ReloadTMR1,ASM,no
INT_Handler TMR1_INT,_pwmint,PBP,yes
endm
INT_CREATE       
ENDASM

    
' Timers configuration
@Freq=4050   
@Prescaler=1                  
T1CON=$00


' Interrupts enable
@INT_ENABLE TMR1_INT
GOSUB StartTimer 


' Main program loop
mainlp:

' Debug display
if flag=0 then
LCDOUT $FE,$2,"Freq. adjust :"
LCDOUT $FE,$C0, DEC frequency
if PORTC.4=1 then frequency=frequency-1
if PORTC.5=1 then frequency=frequency+1
IF PORTC.4 AND PORTC.5=1 then flag=%1
else
LCDOUT $FE,$2,"Amp. adjust :"
LCDOUT $FE,$C0,DEC4 amplitude
if PORTC.4=1 then amplitude=amplitude-1
if PORTC.5=1 then amplitude=amplitude+1
endif

goto mainlp


' PWM calculation and update interrupt (Timer 1) 
pwmint:

' PWM U phase calculation
uduty=sine[ustep]
uduty=uduty<<4**amplitude

' PWM V phase calculation
vduty=sine[vstep]
vduty=vduty<<4**amplitude

' PWM W phase calculation
wduty=sine[wstep]
wduty=wduty<<4**amplitude

' PWM U, V and W update
PDC0L=uduty.lowbyte
PDC0H=uduty.highbyte
PDC1L=vduty.lowbyte
PDC1H=vduty.highbyte
PDC2L=wduty.lowbyte
PDC2H=wduty.highbyte

' Phase angle calculation
ustep=ustep-1
vstep=vstep-1
wstep=wstep-1

' Phase angle reinitialization
if ustep=0 then ustep=90
if vstep=0 then vstep=90
if wstep=0 then wstep=90

@INT_RETURN


' Timer1 interrupt handler
ASM                               
ReloadInst=8                  
MaxCount=65536+(ReloadInst/Prescaler)
TimerReload=MaxCount-(OSC*1000000/4/Prescaler/Freq)
ENDASM


' Timer1 variables
@Timer1=TMR1L                   
Timer1 VAR WORD EXT
TimerReload CON EXT              
TMR1ON VAR T1CON.0        


' Timer1 reload
ASM
ReloadTMR1
MOVE?CT 0,T1CON,TMR1ON     
MOVLW LOW(TimerReload)    
ADDWF TMR1L,F             
BTFSC STATUS,C             
INCF TMR1H,F           
MOVLW HIGH(TimerReload)   
ADDWF TMR1H,F             
MOVE?CT 1,T1CON,TMR1ON     
INT_RETURN
ENDASM


' Timer1 start/stop control
StartTimer:
Timer1=TimerReload         
TMR1ON=1                    
RETURN

StopTimer:
TMR1ON=0                 
RETURN

Also, this afternoon, I will modify the ISR and replace it with TOGGLE PORTB.0, to measure interrupt frequency. I'll give you results.

[HenrikOlsson]

Now you are mixing your original code with Darrels template and what I tried to tell you earlier into a complete mess....

The only thing I want is control the TMR1 interrupt frequency precisely, even in runtime.

Yes, and to do that you change the reload value which you load TMR1 with at each interrupt. In the timer1 intterupt stop the timer, add your reload value to the value of the timer and restart it. Then do whatever else needs to be done in the ISR. Did you try the code I posted in my first reply?

[HenrikOlsson]

Adding to previous message: The higher in interrupt frequency you go the less "resolution" in interrupt frequency you'll get. As an example, preloading the the timer with 65535 would make it go a single tick bwetween interrupts, in other words an interrupt frequency of 2.5Mhz when using a 20MHz crystal. (Won't work in reality but serves the purpose of this discussion).

Now, preloading the timer with 65534 would cut that interrupt frequency in half to 1.25Mhz.

At the other end of the spectrum, going from a preload value of 0 to a preload value of 1 only changes the interrupt frequency by something like 0.001Hz.

The higher the "base frequency" is (the PIC clock in this case) the more resolution you'll get at the upper end.

So, in order to get a linear output frequency you need to calculate the correct preload value, either at runtime ot use a lookuptable and interpolate between points or something.

[pxidr84]

Now you are mixing your original code with Darrels template and what I tried to tell you earlier into a complete mess....


Yes, and to do that you change the reload value which you load TMR1 with at each interrupt. In the timer1 intterupt stop the timer, add your reload value to the value of the timer and restart it. Then do whatever else needs to be done in the ISR. Did you try the code I posted in my first reply?

Of course I've readed your first reply, and it's how I integrated your routine into my code :

' PIC initialization
DEFINE OSC 40      
DEFINE LCD_DREG PORTC
DEFINE LCD_EREG PORTD
DEFINE LCD_RSREG PORTD
DEFINE LCD_EBIT 0
DEFINE LCD_RSBIT 1
DEFINE LCD_COMMANDUS 4000
DEFINE LCD_DATAUS 1000


' BAS includes
INCLUDE "DT_INTS-18.bas"
INCLUDE "ReEnterPBP-18.bas"
INCLUDE "Sine_table.bas"


' Port registers configuration
TRISB=%11000000   ' PWM 0,1,2,3,4,5 outputs
TRISC=%00110000   ' +/- buttons


' PCPWM registers configuration
DTCON=%110        ' Deadtime (600ns)
PTCON0=%0         ' 1:1 postscale, Fosc/4 1:1 prescale, free running mode
PTCON1=%10000000  ' PWM time base is ON, counts up, 19.45kHz/4
PWMCON0=%1000000  ' PWM 0,1,2,3,4,5 set in pair mode
PWMCON1=%1        ' PWM timer sync configuration


' PWM calculation variables
ustep var byte
vstep var byte
wstep var byte
uduty var word
vduty var word
wduty var word
timer var word
amplitude var word
carrier VAR word
flag var bit


' Variables definition
ustep=90          ' 360 degrees phase angle
vstep=60          ' 240 degrees phase angle
wstep=30          ' 120 degrees phase angle
timer=64120       ' Timer adjust
amplitude=65535   ' Sinewave amplitude adjust (65535=max amplitude)
carrier=1023      ' Carrier frequency adjust (1023=13kHz)
flag=%0           ' Menu flag


' PWM carrier frequency register configuration
PTPERL=carrier.lowbyte  
PTPERH=carrier.highbyte

  
' Interrupt processors 
ASM
INT_LIST macro
INT_Handler TMR1_INT,_pwmint,PBP,yes
endm
INT_CREATE       
ENDASM

    
' Timers configuration
T1CON=%1


' Interrupts enable
@INT_ENABLE TMR1_INT


' Main program loop
mainlp:

' Debug display
if flag=0 then
LCDOUT $FE,$2,"Freq. adjust :"
LCDOUT $FE,$C0,DEC timer
if PORTC.4=1 then timer=timer-1
if PORTC.5=1 then timer=timer+1
IF PORTC.4 AND PORTC.5=1 then flag=%1
else
LCDOUT $FE,$2,"Amp. adjust :"
LCDOUT $FE,$C0,DEC4 amplitude
if PORTC.4=1 then amplitude=amplitude-1
if PORTC.5=1 then amplitude=amplitude+1
endif

goto mainlp

TimerShadow VAR WORD
TimerReload VAR WORD

TimerReload=64000 'Test

' PWM calculation and update interrupt (Timer 1) 
pwmint:

' Timer 1 update
TMR1L=timer.lowbyte
TMR1H=timer.highbyte

T1CON.0 = 0  'Stop TMR1
TimerShadow.HighByte = TMR1H
TimerShadow.LowByte = TMR1L
TimerShadow = TimerShadow + TimerReload
TMR1H = TimerShadow.HighByte
TMR1L = TimerShadow.LowByte
T1CON.0 = 1  'Restart TMR1

' PWM U phase calculation
uduty=sine[ustep]
uduty=uduty<<4**amplitude

' PWM V phase calculation
vduty=sine[vstep]
vduty=vduty<<4**amplitude

' PWM W phase calculation
wduty=sine[wstep]
wduty=wduty<<4**amplitude

' PWM U, V and W update
PDC0L=uduty.lowbyte
PDC0H=uduty.highbyte
PDC1L=vduty.lowbyte
PDC1H=vduty.highbyte
PDC2L=wduty.lowbyte
PDC2H=wduty.highbyte

' Phase angle calculation
ustep=ustep-1
vstep=vstep-1
wstep=wstep-1

' Phase angle reinitialization
if ustep=0 then ustep=90
if vstep=0 then vstep=90
if wstep=0 then wstep=90

@INT_RETURN

It doesnt work at all, but I think it's how I integrate your routine in the code, badly I think.

And with this :

pwmint:

toggle PORTD.7

@INT_RETURN

I get a 100Hz output frequency on PORTD.7.

[HenrikOlsson]

I get a 100Hz output frequency on PORTD.7.

Yes, but you still need to keep the reloading code in the interrupt routine otherwise the timer will "freewheel" again.

In your code, as the very first thing in the ISR, you are currently overwriting the TMR1 register with the value of a variable called timer.

' PWM calculation and update interrupt (Timer 1) 
pwmint:
 
' Timer 1 update
TMR1L=timer.lowbyte     '<---This is overwriting the TMR1 registers!
TMR1H=timer.highbyte

So, once the code gets to "copying" the TMR1 registers and adding the reload value to it you have overwritten it with something else.

I've just tested the following code here:

DEFINE LOADER_USED 1
DEFINE OSC 20
 
INCLUDE "DT_INTS-18.bas"
INCLUDE "ReEnterPBP-18.bas"
INCLUDE "IncPID.pbp"
 
TMRCopy VAR WORD
TimerReloadValue VAR WORD
TimerReloadValue = 63000
 
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  _TimezUp,   PBP,  yes
    endm
    INT_CREATE              ; Creates the interrupt processor
ENDASM
 
@ INT_ENABLE  TMR1_INT      ; enable Timer 1 interrupts
 
TRISB.0 = 1                 ' +button
TRISA.4 = 1                 ' -button
TRISB.3 = 0                 ' Output to measure interrupt frequency 
 
CMCON = 7
ADCON1 = %00001111          ' No analog inputs.
T1CON.0 = 1                 ' Start TMR1
 
Main:
If PortB.0 = 0 then
  TimerReloadValue = TimerReloadValue + 1
  LCDOUT $FE,1,#TimerReloadValue
ENDIF
If PortA.4 = 0 then
  TimerReloadValue = TimerReloadValue - 1
  LCDOUT $FE,1,#TimerReloadValue
ENDIF
Pause 20
Goto Main
 
' ---------- Interrupt handler ------------
TimezUp:
  T1CON.0 = 0                             ' Stop TMR1
  TMRCopy.HighByte = TMR1H                ' Copy value of TMR1 registers
  TMRCopy.LowByte = TMR1L 
  TMRCopy = TMRCopy + TimerReloadValue    ' Add reload value (compensates for overhead)
  TMR1H = TMRCOPY.HighByte                ' And back to TMR1
  TMR1L = TMRCopy.LowByte
  T1CON.0 = 1                             ' Restart Timer
Toggle PortB.3
@ INT_RETURN

And it works fine. Pushing the buttons connected to PortB.0 and PortA.4 increases/decreases the reload value for the timer and the interrupt frequency.

But, again, a change of 1 at the "top" will not result in the same change in interrupt frequency as a change of 1 at the "botton".

[pxidr84]

Yes, but you still need to keep the reloading code in the interrupt routine otherwise the timer will "freewheel" again.

In your code, as the very first thing in the ISR, you are currently overwriting the TMR1 register with the value of a variable called timer.

' PWM calculation and update interrupt (Timer 1) 
pwmint:
 
' Timer 1 update
TMR1L=timer.lowbyte     '<---This is overwriting the TMR1 registers!
TMR1H=timer.highbyte

So, once the code gets to "copying" the TMR1 registers and adding the reload value to it you have overwritten it with something else.

I've just tested the following code here:

DEFINE LOADER_USED 1
DEFINE OSC 20
 
INCLUDE "DT_INTS-18.bas"
INCLUDE "ReEnterPBP-18.bas"
INCLUDE "IncPID.pbp"
 
TMRCopy VAR WORD
TimerReloadValue VAR WORD
TimerReloadValue = 63000
 
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  _TimezUp,   PBP,  yes
    endm
    INT_CREATE              ; Creates the interrupt processor
ENDASM
 
@ INT_ENABLE  TMR1_INT      ; enable Timer 1 interrupts
 
TRISB.0 = 1                 ' +button
TRISA.4 = 1                 ' -button
TRISB.3 = 0                 ' Output to measure interrupt frequency 
 
CMCON = 7
ADCON1 = %00001111          ' No analog inputs.
T1CON.0 = 1                 ' Start TMR1
 
Main:
If PortB.0 = 0 then
  TimerReloadValue = TimerReloadValue + 1
  LCDOUT $FE,1,#TimerReloadValue
ENDIF
If PortA.4 = 0 then
  TimerReloadValue = TimerReloadValue - 1
  LCDOUT $FE,1,#TimerReloadValue
ENDIF
Pause 20
Goto Main
 
' ---------- Interrupt handler ------------
TimezUp:
  T1CON.0 = 0                             ' Stop TMR1
  TMRCopy.HighByte = TMR1H                ' Copy value of TMR1 registers
  TMRCopy.LowByte = TMR1L 
  TMRCopy = TMRCopy + TimerReloadValue    ' Add reload value (compensates for overhead)
  TMR1H = TMRCOPY.HighByte                ' And back to TMR1
  TMR1L = TMRCopy.LowByte
  T1CON.0 = 1                             ' Restart Timer
Toggle PortB.3
@ INT_RETURN

And it works fine. Pushing the buttons connected to PortB.0 and PortA.4 increases/decreases the reload value for the timer and the interrupt frequency.

But, again, a change of 1 at the "top" will not result in the same change in interrupt frequency as a change of 1 at the "botton".

Tried this in my code with the sines, it works.

But, again, a change of 1 at the "top" will not result in the same change in interrupt frequency as a change of 1 at the "botton".

So what the point since the first program? It is impossible to change proportionally this interrupt frequency in run time? Or any math relation/equation to calculate the correct timer value according to the desired frequency?

Like you said, I can make a lookup table, but this program is intended to make a 3-phase VFD AC motor drive, adjustable from 0 to 120Hz with 0.1Hz increments... so if I use a lookup table, it will take 1200 variables! Doesn't sure that my PIC had enough memory capacity...
And how to calculate the "correct preload value"?

[HenrikOlsson]

The difference is that it takes the overhead of saving all the PBP system variables into account. There's nothing you can do about the non linearity really - it's just the way it is. One way to reduce the effect of it is to have less "steps" in the SIN table, that willm bring the interrupt frequency down which makes the relationship between interrupt frequency and reload value more linear.

You CAN calculate the reload value at runtime, Darrels timer template even shows you HOW to do it (at compile/assembly time) but you need to play some tricks to do it runtime. The following is NOT tested:

Dummy VAR WORD
Dummy2 VAR WORD
Dummy3 VAR WORD
ReloadInstructions VAR BYTE
TimerReload VAR WORD
Frequency VAR WORD

ReloadInstruction = 0  'Number of instructioncycles it takes to actually reload the timer. I don't know how many it is in this case. Tune later.

'For 40Mhz operation and 1:1 prescaler the timer ticks at 10Mhz
Dummy2 = 10000     'These can not be constants because 
Dummy3 = 10000     'constants doesn't work with DIV32

Frequency = 200    'Lowest possible frequency is ~153Hz. Don't go below that.

Dummy = Dummy2 * Dummy3        'Intermediate result is now 10.000.000
TimerReload = DIV32 Frequency       'Divide 10.000.000 in Frequency (200 in this case) 
TimerReload = 65535 - TimerReload + 1 + ReloadInstructions  ' =15536 for 200Hz

'Reloading the timer with 15536 makes it time out in 50000 ticks, one tick is 0.1us so
'it times out it 5000us or 5ms, 1/0.005=200Hz which is the frequency we wanted.

This should calculate the reload value, at runtime (don't do this IN the interrupt service routine). But I don't think you'll get 0.1Hz resolution at the top end.

[pxidr84]

Thanks, I will make some experiments with this code.

[pxidr84]

Unfortuntely, it doesn't works.

The problem is that TimerReload variable overwrites TimerReload EXT constant, defined later in DT routine.

' PIC initialization
DEFINE OSC 40      
DEFINE LCD_DREG PORTC
DEFINE LCD_EREG PORTD
DEFINE LCD_RSREG PORTD
DEFINE LCD_EBIT 0
DEFINE LCD_RSBIT 1
DEFINE LCD_COMMANDUS 4000
DEFINE LCD_DATAUS 1000


' BAS includes
INCLUDE "DT_INTS-18.bas"
INCLUDE "ReEnterPBP-18.bas"
INCLUDE "Sine_table.bas"


' Port registers configuration
TRISB=%11000000   ' PWM 0,1,2,3,4,5 outputs
TRISC=%00110000   ' +/- buttons


' PCPWM registers configuration
DTCON=%110        ' Deadtime (600ns)
PTCON0=%0         ' 1:1 postscale, Fosc/4 1:1 prescale, free running mode
PTCON1=%10000000  ' PWM time base is ON, counts up, 19.45kHz/4
PWMCON0=%1000000  ' PWM 0,1,2,3,4,5 set in pair mode
PWMCON1=%1        ' PWM timer sync configuration


' PWM calculation variables
ustep var byte
vstep var byte
wstep var byte
uduty var word
vduty var word
wduty var word
amplitude var word
carrier VAR word
flag var bit


' Variables definition
ustep=90          ' 360 degrees phase angle
vstep=60          ' 240 degrees phase angle
wstep=30          ' 120 degrees phase angle
amplitude=65535   ' Sinewave amplitude adjust (65535=max amplitude)
carrier=1023      ' Carrier frequency adjust (1023=13kHz)
flag=%0           ' Menu flag


' PWM carrier frequency register configuration
PTPERL=carrier.lowbyte  
PTPERH=carrier.highbyte

Dummy VAR WORD
Dummy2 VAR WORD
Dummy3 VAR WORD
ReloadInstruction VAR BYTE
TimerReload VAR WORD
Frequency VAR WORD


ReloadInstruction = 0  'Number of instructioncycles it takes to actually reload the timer. I don't know how many it is in this case. Tune later.

'For 40Mhz operation and 1:1 prescaler the timer ticks at 10Mhz
Dummy2 = 10000     'These can not be constants because 
Dummy3 = 10000     'constants doesn't work with DIV32

Frequency = 5000    'Lowest possible frequency is ~153Hz. Don't go below that.

Dummy = Dummy2 * Dummy3        'Intermediate result is now 10.000.000
TimerReload = DIV32 Frequency       'Divide 10.000.000 in Frequency (200 in this case) 
TimerReload = 65535 - TimerReload + 1 + ReloadInstruction  ' =15536 for 200Hz


' Interrupt processors 
ASM
INT_LIST macro
INT_Handler TMR1_INT,ReloadTMR1,ASM,no
INT_Handler TMR1_INT,_pwmint,PBP,yes
endm
INT_CREATE       
ENDASM

    
' Timers configuration
@Freq=4050   
@Prescaler=1                  
T1CON=$00


' Interrupts enable
@INT_ENABLE TMR1_INT
GOSUB StartTimer 


' Main program loop
mainlp:

' Debug display
if flag=0 then
LCDOUT $FE,$2,"Freq. adjust :"
LCDOUT $FE,$C0, DEC frequency
if PORTC.4=1 then frequency=frequency-1
if PORTC.5=1 then frequency=frequency+1
IF PORTC.4 AND PORTC.5=1 then flag=%1
else
LCDOUT $FE,$2,"Amp. adjust :"
LCDOUT $FE,$C0,DEC4 amplitude
if PORTC.4=1 then amplitude=amplitude-1
if PORTC.5=1 then amplitude=amplitude+1
endif

goto mainlp


' PWM calculation and update interrupt (Timer 1) 
pwmint:

' PWM U phase calculation
uduty=sine[ustep]
uduty=uduty<<4**amplitude

' PWM V phase calculation
vduty=sine[vstep]
vduty=vduty<<4**amplitude

' PWM W phase calculation
wduty=sine[wstep]
wduty=wduty<<4**amplitude

' PWM U, V and W update
PDC0L=uduty.lowbyte
PDC0H=uduty.highbyte
PDC1L=vduty.lowbyte
PDC1H=vduty.highbyte
PDC2L=wduty.lowbyte
PDC2H=wduty.highbyte

' Phase angle calculation
ustep=ustep-1
vstep=vstep-1
wstep=wstep-1

' Phase angle reinitialization
if ustep=0 then ustep=90
if vstep=0 then vstep=90
if wstep=0 then wstep=90

@INT_RETURN


' Timer1 interrupt handler
ASM                               
ReloadInst=8                  
MaxCount=65536+(ReloadInst/Prescaler)
TimerReload=MaxCount-(OSC*1000000/4/Prescaler/Freq)
ENDASM


' Timer1 variables
@Timer1=TMR1L                   
Timer1 VAR WORD EXT
'TimerReload VAR EXT              
TMR1ON VAR T1CON.0        


' Timer1 reload
ASM
ReloadTMR1
MOVE?CT 0,T1CON,TMR1ON     
MOVLW LOW(TimerReload)    
ADDWF TMR1L,F             
BTFSC STATUS,C             
INCF TMR1H,F           
MOVLW HIGH(TimerReload)   
ADDWF TMR1H,F             
MOVE?CT 1,T1CON,TMR1ON     
INT_RETURN
ENDASM


' Timer1 start/stop control
StartTimer:
Timer1=TimerReload         
TMR1ON=1                    
RETURN

StopTimer:
TMR1ON=0                 
RETURN

[HenrikOlsson]

Yes of course it does. I thought we came to the conclusion that you couldn't use Darrels timer template because it calculated the reload value at build time and you wanted to calculate it at runtime. Now you're trying to use it anyway....I don't get it.

INCLUDE "DT_INTS-18.bas"
INCLUDE "ReEnterPBP-18.bas"
 
InterruptFrequency VAR WORD
Dummy VAR WORD
Dummy2 VAR WORD
Dummy3 VAR WORD
TMRCopy VAR WORD
TimerReloadValue VAR WORD
Dummy2 = 10000
Dummy3 = 10000
 
InterruptFrequency = 5000
 
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  _TimezUp,   PBP,  yes
    endm
    INT_CREATE              ; Creates the interrupt processor
ENDASM
 
@ INT_ENABLE  TMR1_INT      ; enable Timer 1 interrupts
 
TRISB.3 = 0                 ' Output to measure interrupt frequency 
CMCON = 7
ADCON1 = %00001111          ' No analog inputs.
 
T1CON.0 = 1                 ' Start TMR1
 
  Dummy = Dummy2 * Dummy3
  TimerReloadValue = Div32 InterruptFrequency
  TimerReloadValue = 65535 - TimerReloadValue + 1
  LCDOUT $FE,1,"F: ", #InterruptFrequency, " Reload: ", #TimerReloadValue
 
Main:
 Pause 20
Goto Main
 
' ---------- Interrupt handler ------------
TimezUp:
  T1CON.0 = 0                             ' Stop TMR1
  TMRCopy.HighByte = TMR1H                ' Copy value of TMR1 registers
  TMRCopy.LowByte = TMR1L 
  TMRCopy = TMRCopy + TimerReloadValue    ' Add reload value (compensates for overhead)
  TMR1H = TMRCOPY.HighByte                ' And back to TMR1
  TMR1L = TMRCopy.LowByte
  T1CON.0 = 1                             ' Restart Timer
Toggle PortB.3
 
@ INT_RETURN

[pxidr84]

Yes of course it does. I thought we came to the conclusion that you couldn't use Darrels timer template because it calculated the reload value at build time and you wanted to calculate it at runtime. Now you're trying to use it anyway....I don't get it.

INCLUDE "DT_INTS-18.bas"
INCLUDE "ReEnterPBP-18.bas"
 
InterruptFrequency VAR WORD
Dummy VAR WORD
Dummy2 VAR WORD
Dummy3 VAR WORD
TMRCopy VAR WORD
TimerReloadValue VAR WORD
Dummy2 = 10000
Dummy3 = 10000
 
InterruptFrequency = 5000
 
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  _TimezUp,   PBP,  yes
    endm
    INT_CREATE              ; Creates the interrupt processor
ENDASM
 
@ INT_ENABLE  TMR1_INT      ; enable Timer 1 interrupts
 
TRISB.3 = 0                 ' Output to measure interrupt frequency 
CMCON = 7
ADCON1 = %00001111          ' No analog inputs.
 
T1CON.0 = 1                 ' Start TMR1
 
  Dummy = Dummy2 * Dummy3
  TimerReloadValue = Div32 InterruptFrequency
  TimerReloadValue = 65535 - TimerReloadValue + 1
  LCDOUT $FE,1,"F: ", #InterruptFrequency, " Reload: ", #TimerReloadValue
 
Main:
 Pause 20
Goto Main
 
' ---------- Interrupt handler ------------
TimezUp:
  T1CON.0 = 0                             ' Stop TMR1
  TMRCopy.HighByte = TMR1H                ' Copy value of TMR1 registers
  TMRCopy.LowByte = TMR1L 
  TMRCopy = TMRCopy + TimerReloadValue    ' Add reload value (compensates for overhead)
  TMR1H = TMRCOPY.HighByte                ' And back to TMR1
  TMR1L = TMRCopy.LowByte
  T1CON.0 = 1                             ' Restart Timer
Toggle PortB.3
 
@ INT_RETURN

Excuse me, I thought that your code was destinated for the DT template, I'm quite lost in reality.
I will try this tonight.

[pxidr84]

I've tested your code, and the results are quite encouraging.

Some tests I've done :

INTF=38000 Output=56Hz
INTF=35000 Output=51.6Hz
INTF=30000 Output=44.3Hz

For each, INTF/Output=678, so it's "linear" now.

But when the interrupt frequency is above ~39060Hz, the ReloadTimer jumps from ~62975 to ~63405 ! Of course, the sines jumps ~10Hz upper.

' PIC initialization
DEFINE OSC 40      
DEFINE LCD_DREG PORTC
DEFINE LCD_EREG PORTD
DEFINE LCD_RSREG PORTD
DEFINE LCD_EBIT 0
DEFINE LCD_RSBIT 1
DEFINE LCD_COMMANDUS 4000
DEFINE LCD_DATAUS 1000


' BAS includes
INCLUDE "DT_INTS-18.bas"
INCLUDE "ReEnterPBP-18.bas"
INCLUDE "Sine_table.bas"


' Port registers configuration
TRISB=%11000000   ' PWM 0,1,2,3,4,5 outputs
TRISC=%00110000   ' +/- buttons


' PCPWM registers configuration
DTCON=%110        ' Deadtime (600ns)
PTCON0=%0         ' 1:1 postscale, Fosc/4 1:1 prescale, free running mode
PTCON1=%10000000  ' PWM time base is ON, counts up, 19.45kHz/4
PWMCON0=%1000000  ' PWM 0,1,2,3,4,5 set in pair mode
PWMCON1=%1        ' PWM timer sync configuration


' PWM calculation variables
ustep var byte
vstep var byte
wstep var byte
uduty var word
vduty var word
wduty var word
amplitude var word
carrier VAR word
flag var bit


' Variables definition
ustep=90          ' 360 degrees phase angle
vstep=60          ' 240 degrees phase angle
wstep=30          ' 120 degrees phase angle
amplitude=65535   ' Sinewave amplitude adjust (65535=max amplitude)
carrier=1023      ' Carrier frequency adjust (1023=13kHz)
flag=0           ' Menu flag


' PWM carrier frequency register configuration
PTPERL=carrier.lowbyte  
PTPERH=carrier.highbyte


InterruptFrequency VAR WORD
Dummy VAR WORD
Dummy2 VAR WORD
Dummy3 VAR WORD
TMRCopy VAR WORD
TimerReloadValue VAR WORD
InterruptFrequency = 38000


' Interrupt processors 
ASM
INT_LIST macro
INT_Handler TMR1_INT,_pwmint,PBP,yes
endm
INT_CREATE       
ENDASM


' Interrupts enable
@INT_ENABLE TMR1_INT
T1CON.0=1

recalc:
Dummy2 = 10000
Dummy3 = 10000
Dummy = Dummy2 * Dummy3
TimerReloadValue = Div32 InterruptFrequency
TimerReloadValue = 65535 - TimerReloadValue  + 1

' Main program loop
mainlp:

flag=0
LCDOUT $FE,2,"F: ", #InterruptFrequency
lcdout $FE, $C0," R: ", #TimerReloadValue
if PORTC.4=1 then InterruptFrequency=InterruptFrequency-1 : flag=1
if PORTC.5=1 then InterruptFrequency=InterruptFrequency+1 : flag=1
if flag=1 then goto recalc

goto mainlp


' PWM calculation and update interrupt (Timer 1) 
pwmint:

T1CON.0 = 0                             ' Stop TMR1
TMRCopy.HighByte = TMR1H                ' Copy value of TMR1 registers
TMRCopy.LowByte = TMR1L 
TMRCopy = TMRCopy + TimerReloadValue    ' Add reload value (compensates for overhead)
TMR1H = TMRCOPY.HighByte                ' And back to TMR1
TMR1L = TMRCopy.LowByte
T1CON.0 = 1                             ' Restart Timer

' PWM U phase calculation
uduty=sine[ustep]
uduty=uduty<<4**amplitude

' PWM V phase calculation
vduty=sine[vstep]
vduty=vduty<<4**amplitude

' PWM W phase calculation
wduty=sine[wstep]
wduty=wduty<<4**amplitude

' PWM U, V and W update
PDC0L=uduty.lowbyte
PDC0H=uduty.highbyte
PDC1L=vduty.lowbyte
PDC1H=vduty.highbyte
PDC2L=wduty.lowbyte
PDC2H=wduty.highbyte

' Phase angle calculation
ustep=ustep-1
vstep=vstep-1
wstep=wstep-1

' Phase angle reinitialization
if ustep=0 then ustep=90
if vstep=0 then vstep=90
if wstep=0 then wstep=90

@INT_RETURN

[HenrikOlsson]

Hi,
Interrupt frequency of 39060Hz?

Previously you said you wanted an output of 120Hz and with 72 steps per sin-cycle that's 120*72=8640Hz interrupt frequency. The math is then like this

65535 - (10,000,000 / 8640) + 1 = 64378

64378 is what the timer reload value is and this means that there's 65536-64378=1158 cycles between interrupts. 1158 cycles times 100ns per cycle equals 115.8us between interrupts 1/115.8us = 8635Hz so it's pretty close.

This means that there's only 1158 cycles (or instructions if you will) between interrupts. In this time the PIC has to save all the PBP system variables, reload the timer, execute your interrupt service routine and then restore all the PBP system variables.

Why are you trying to interrupt at ~39kHz? That's only about 256 cycles between interrupts which I'm pretty sure won't be enough time to do all that needs to get done in the interrupt.

Finally, this line:

If PortC.4 = 1 Then InterruptFrequency = InterruptFrequency -1 : Flag = 1

Probably doesn't work like you think. Here, Flag gets set no matter what the state of of PortC.4 actually is. So you are always running the recalc routine. If you want Flag to be set only when PortC.4 is high you need to change it to:

If PortC.4 = 1 THEN
  InterruptFrequency = InterruptFrequency - 1
  Flag = 1
ENDIF

[pxidr84]

Hi,
Interrupt frequency of 39060Hz?

Previously you said you wanted an output of 120Hz and with 72 steps per sin-cycle that's 120*72=8640Hz interrupt frequency. The math is then like this

65535 - (10,000,000 / 8640) + 1 = 64378

64378 is what the timer reload value is and this means that there's 65536-64378=1158 cycles between interrupts. 1158 cycles times 100ns per cycle equals 115.8us between interrupts 1/115.8us = 8635Hz so it's pretty close.

This means that there's only 1158 cycles (or instructions if you will) between interrupts. In this time the PIC has to save all the PBP system variables, reload the timer, execute your interrupt service routine and then restore all the PBP system variables.

Why are you trying to interrupt at ~39kHz? That's only about 256 cycles between interrupts which I'm pretty sure won't be enough time to do all that needs to get done in the interrupt.

Finally, this line:

If PortC.4 = 1 Then InterruptFrequency = InterruptFrequency -1 : Flag = 1

Probably doesn't work like you think. Here, Flag gets set no matter what the state of of PortC.4 actually is. So you are always running the recalc routine. If you want Flag to be set only when PortC.4 is high you need to change it to:

If PortC.4 = 1 THEN
  InterruptFrequency = InterruptFrequency - 1
  Flag = 1
ENDIF

Well, for 120Hz, I need an interrupt frequency of 120*90=10800Hz.
If I configure this in my program, I get output sines of only ~16Hz.

So what's wrong?

The code :

' PIC initialization
DEFINE OSC 40      
DEFINE LCD_DREG PORTC
DEFINE LCD_EREG PORTD
DEFINE LCD_RSREG PORTD
DEFINE LCD_EBIT 0
DEFINE LCD_RSBIT 1
DEFINE LCD_COMMANDUS 4000
DEFINE LCD_DATAUS 1000


' BAS includes
INCLUDE "DT_INTS-18.bas"
INCLUDE "ReEnterPBP-18.bas"
INCLUDE "Sine_table.bas"


' Port registers configuration
TRISB=%11000000   ' PWM 0,1,2,3,4,5 outputs
TRISC=%00110000   ' +/- buttons


' PCPWM registers configuration
DTCON=%110        ' Deadtime (600ns)
PTCON0=%0         ' 1:1 postscale, Fosc/4 1:1 prescale, free running mode
PTCON1=%10000000  ' PWM time base is ON, counts up, 19.45kHz/4
PWMCON0=%1000000  ' PWM 0,1,2,3,4,5 set in pair mode
PWMCON1=%1        ' PWM timer sync configuration


' PWM calculation variables
ustep var byte
vstep var byte
wstep var byte
uduty var word
vduty var word
wduty var word
amplitude var word
carrier VAR word
flag var bit
Dummy VAR WORD
Dummy2 VAR WORD
Dummy3 VAR WORD
InterruptFrequency VAR WORD
TMRCopy VAR WORD
TimerReloadValue VAR WORD


' Variables definition
ustep=90          ' 360 degrees phase angle
vstep=60          ' 240 degrees phase angle
wstep=30          ' 120 degrees phase angle
amplitude=65535   ' Sinewave amplitude adjust (65535=max amplitude)
carrier=1023      ' Carrier frequency adjust (1023=13kHz)
flag=0           ' Menu flag
Dummy2 = 10000
Dummy3 = 10000
InterruptFrequency = 10800


' PWM carrier frequency register configuration
PTPERL=carrier.lowbyte  
PTPERH=carrier.highbyte


' Interrupt processors 
ASM
INT_LIST macro
INT_Handler TMR1_INT,_pwmint,PBP,yes
endm
INT_CREATE       
ENDASM


' Interrupts enable
@INT_ENABLE TMR1_INT
T1CON.0=1

recalc:
Dummy = Dummy2 * Dummy3
TimerReloadValue = Div32 InterruptFrequency
TimerReloadValue = 65535 - TimerReloadValue  + 1
flag=0


' Main program loop
mainlp:

LCDOUT $FE,2,"F: ",#InterruptFrequency
lcdout $FE,$C0,"R: ",#TimerReloadValue
if PORTC.4=1 then 
InterruptFrequency=InterruptFrequency-1 
flag=1
ENDIF
if PORTC.5=1 then 
InterruptFrequency=InterruptFrequency+1
flag=1
ENDIF

if flag=1 then goto recalc

goto mainlp


' PWM calculation and update interrupt (Timer 1) 
pwmint:

T1CON.0 = 0                             ' Stop TMR1
TMRCopy.HighByte = TMR1H                ' Copy value of TMR1 registers
TMRCopy.LowByte = TMR1L 
TMRCopy = TMRCopy + TimerReloadValue    ' Add reload value (compensates for overhead)
TMR1H = TMRCOPY.HighByte                ' And back to TMR1
TMR1L = TMRCopy.LowByte
T1CON.0 = 1                             ' Restart Timer

' PWM U phase calculation
uduty=sine[ustep]
uduty=uduty<<4**amplitude

' PWM V phase calculation
vduty=sine[vstep]
vduty=vduty<<4**amplitude

' PWM W phase calculation
wduty=sine[wstep]
wduty=wduty<<4**amplitude

' PWM U, V and W update
PDC0L=uduty.lowbyte
PDC0H=uduty.highbyte
PDC1L=vduty.lowbyte
PDC1H=vduty.highbyte
PDC2L=wduty.lowbyte
PDC2H=wduty.highbyte

' Phase angle calculation
ustep=ustep-1
vstep=vstep-1
wstep=wstep-1

' Phase angle reinitialization
if ustep=0 then ustep=90
if vstep=0 then vstep=90
if wstep=0 then wstep=90

@INT_RETURN

The "flag" problem is corrected now, I can change frequency during runtime.

And there is my sine table (if needed) :

' Sine table (4 degrees/step, 90*4=360 degrees)
sine var byte[90]
sine[1]=128
sine[2]=137
sine[3]=146
sine[4]=155
sine[5]=163
sine[6]=172
sine[7]=180
sine[8]=188
sine[9]=196
sine[10]=203
sine[11]=210
sine[12]=217
sine[13]=223
sine[14]=229
sine[15]=234
sine[16]=239
sine[17]=243
sine[18]=247
sine[19]=250
sine[20]=252
sine[21]=254
sine[22]=255
sine[23]=255
sine[24]=255
sine[25]=255
sine[26]=254
sine[27]=252
sine[28]=250
sine[29]=247
sine[30]=243
sine[31]=239
sine[32]=234
sine[33]=229
sine[34]=223
sine[35]=217
sine[36]=210
sine[37]=203
sine[38]=196
sine[39]=188
sine[40]=180
sine[41]=172
sine[42]=163
sine[43]=155
sine[44]=146
sine[45]=137
sine[46]=128
sine[47]=119
sine[48]=110
sine[49]=101
sine[50]=93
sine[51]=84
sine[52]=76
sine[53]=68
sine[54]=60
sine[55]=53
sine[56]=46
sine[57]=39
sine[58]=33
sine[59]=27
sine[60]=22
sine[61]=17
sine[62]=13
sine[63]=9
sine[64]=6
sine[65]=4
sine[66]=2
sine[67]=1
sine[68]=0
sine[69]=0
sine[70]=1
sine[71]=2
sine[72]=4
sine[73]=6
sine[74]=9
sine[75]=13
sine[76]=17
sine[77]=22
sine[78]=27
sine[79]=33
sine[80]=39
sine[81]=46
sine[82]=53
sine[83]=60
sine[84]=68
sine[85]=76
sine[86]=84
sine[87]=93
sine[88]=101
sine[89]=110
sine[90]=119

[HenrikOlsson]

Hi,
OK, I don't know from where I got that you had 72 steps in the lookup table. Now I know it's 90. If can live with fewer steps you'll be able to increase the output frequency.

I'm pretty sure you're simply running out of time. I made some quick tests here but in order to do so I had to change your code a little bit (don't have 4431 handy to test on). So I'm not sure exactly how much we can depend on these.

I'm using a 18F4520 @20Mhz.

The interrupt routine itself runs in about 70us, the overhead introduced by the interrupt system (DT-ints) is from previous tests I've done about 29us (again at 20Mhz) at interrupt entry and I would guess about the same on exit. This means each interrupt takes a total of ~130us.

1/0.000130 = 7700Hz

I've verified this by specifying InterruptFrequency of 7700Hz and it works, I get 7700 Hz with nice, steady pulses. If I specify 8500Hz I can see on the scope that the trace is starting to get jittery indicating that it's starting to overrun it self, missing pulses so think I'm pretty close to the absolute max at 7500-8000Hz.

Now, in theory, since you're running at 40MHz you should be able to get twice that, ~15kHz but apparently you're not. Can you set a pin high at the beginning of the interrupt service routine and set it low just before @INT_RETURN, then measure how long that output is high. That will tell you the execution time of the actual handler (where I got 70us).

Are you sure that the PIC is running at 40Mhz? Simply specifying DEFINE OSC40 doesn't make it run at 40MHZ, you need to enable the PLL thru the CONFIG bits as well.

/Henrik.

[pxidr84]

Hi,
OK, I don't know from where I got that you had 72 steps in the lookup table. Now I know it's 90. If can live with fewer steps you'll be able to increase the output frequency.

I'm pretty sure you're simply running out of time. I made some quick tests here but in order to do so I had to change your code a little bit (don't have 4431 handy to test on). So I'm not sure exactly how much we can depend on these.

I'm using a 18F4520 @20Mhz.

The interrupt routine itself runs in about 70us, the overhead introduced by the interrupt system (DT-ints) is from previous tests I've done about 29us (again at 20Mhz) at interrupt entry and I would guess about the same on exit. This means each interrupt takes a total of ~130us.

1/0.000130 = 7700Hz

I've verified this by specifying InterruptFrequency of 7700Hz and it works, I get 7700 Hz with nice, steady pulses. If I specify 8500Hz I can see on the scope that the trace is starting to get jittery indicating that it's starting to overrun it self, missing pulses so think I'm pretty close to the absolute max at 7500-8000Hz.

Now, in theory, since you're running at 40MHz you should be able to get twice that, ~15kHz but apparently you're not. Can you set a pin high at the beginning of the interrupt service routine and set it low just before @INT_RETURN, then measure how long that output is high. That will tell you the execution time of the actual handler (where I got 70us).

Are you sure that the PIC is running at 40Mhz? Simply specifying DEFINE OSC40 doesn't make it run at 40MHZ, you need to enable the PLL thru the CONFIG bits as well.

/Henrik.

With this :

' PWM calculation and update interrupt (Timer 1) 
pwmint:

T1CON.0 = 0                             ' Stop TMR1
TMRCopy.HighByte = TMR1H                ' Copy value of TMR1 registers
TMRCopy.LowByte = TMR1L 
TMRCopy = TMRCopy + TimerReloadValue    ' Add reload value (compensates for overhead)
TMR1H = TMRCOPY.HighByte                ' And back to TMR1
TMR1L = TMRCopy.LowByte
T1CON.0 = 1                             ' Restart Timer

TOGGLE PORTD.7

@INT_RETURN

And a interrupt freq of 10800Hz, I get an output square wave of 720Hz on the oscilloscope.

Here is my config bits in MPLAB :


Note I'm using the HS oscillator with PLL enabled. My crystal (40MHz) is connected between OSC1 and OSC2 pins, with 2*47pF ceramic capacitors. On the oscilloscope, it's okay, I can see the oscillation.

[HenrikOlsson]

Hi,
Something must be wrong with your setup. I tried the same ISR as your one, with InterruptFrequency = 10800:

' ---------- Interrupt handler ------------
TimezUp:
PortB.3 = 1
  T1CON.0 = 0                             ' Stop TMR1
  TMRCopy.HighByte = TMR1H                ' Copy value of TMR1 registers
  TMRCopy.LowByte = TMR1L 
  TMRCopy = TMRCopy + TimerReloadValue    ' Add reload value (compensates for overhead)
  TMR1H = TMRCOPY.HighByte                ' And back to TMR1
  TMR1L = TMRCopy.LowByte
  T1CON.0 = 1                             ' Restart Timer
PortB.3 = 0
@ INT_RETURN

And I get ~10500Hz even when running at 20Mhz. Here you can see that I, instead of using TOGGLE set the output high at the entry point and low at the exit which allows me to measure the execution time of the code in between. This exact code executes in ~3us on this 18F4520 running at 20MHz, if you try the same on yours it should be 1.5us - if it's not then you're not running at 40MHz.

You say you have a 40MHz x-tal, is that really correct? To run at 40MHz with the PLL you should use a 10MHz x-tal.

Try the above, what's the pulsewidth on the output? If it's not 1.5us you're not running at 40MHz.

/Henrik.

[pxidr84]

Hi,
Something must be wrong with your setup. I tried the same ISR as your one, with InterruptFrequency = 10800:

' ---------- Interrupt handler ------------
TimezUp:
PortB.3 = 1
  T1CON.0 = 0                             ' Stop TMR1
  TMRCopy.HighByte = TMR1H                ' Copy value of TMR1 registers
  TMRCopy.LowByte = TMR1L 
  TMRCopy = TMRCopy + TimerReloadValue    ' Add reload value (compensates for overhead)
  TMR1H = TMRCOPY.HighByte                ' And back to TMR1
  TMR1L = TMRCopy.LowByte
  T1CON.0 = 1                             ' Restart Timer
PortB.3 = 0
@ INT_RETURN

And I get ~10500Hz even when running at 20Mhz. Here you can see that I, instead of using TOGGLE set the output high at the entry point and low at the exit which allows me to measure the execution time of the code in between. This exact code executes in ~3us on this 18F4520 running at 20MHz, if you try the same on yours it should be 1.5us - if it's not then you're not running at 40MHz.

You say you have a 40MHz x-tal, is that really correct? To run at 40MHz with the PLL you should use a 10MHz x-tal.

Try the above, what's the pulsewidth on the output? If it's not 1.5us you're not running at 40MHz.

/Henrik.

With your exact code (the same you're using) and a INTF of 10800Hz, I get 2,76ms between each pulse. Very weird, and very slow. I've disabled the PLL, the oscilator is configured as a HS oscillator.

[HenrikOlsson]

Hi,
1) What's the width of the pulses? Not the time between them but the width?
2) What's the value stamped on your x-tal?
3) The timing calculations that I provided are based on the fact that your chip is SUPPOSED to run at 40MHz, if it's not running at 40MHz then the timing will be wrong and the interrupt frequency will wrong as well.
4) Please don't quote the complete message you're responding to. It clutters the thread and it gets hard read because everything is quoted all the time - that's my personal view.

[pxidr84]

The pulses are very very thin :



The width of a pulse is 4,4µs.

Of course the crystal is stamped at 40MHz, I've difficulties with the setup of this timer, but I hope I'm not an idiot

The circuit :

[HenrikOlsson]

Of course the crystal is stamped at 40MHz

Well, then that is likely the problem - or one of them... If you look at page 355 in the datasheet you'll see that the maximum x-tal frequency WITHOUT PLL is 25 MHz and with using the PLL it's 10MHz (resulting in 40Mhz). You're trying to use 40Mhz which is out of specs in both cases.

The fact that your pulses are 4.4us wide while mine are 3us means that your chip is running way SLOWER than mine while in fact it "should" be running twice as fast.

Get the oscillator sorted and verify that the PIC is running at the speed you think. One way to do that is a simple program like:

DEFINE OSC 20    'Don't forget to DEFINE the correct OSC speed.
TRISB.0 = 0
Main:
  PortB.0 = 1
  Pause 1
  PortB.0 = 0
  Pause 1
Goto Main.

If you DON't get a 500Hz signal with 1ms wide pulses the chip isn't running at the correct and/or DEFINE'd oscillator speed.

[pxidr84]

Okay, sincelery I'm quite new with the PICs, so I doesn't know this "problem" (in reality is not a problem).

I'll try to find a slower crystal tomorrow.

[pxidr84]

Okay, so I've unsoldered an 8MHz xtal (not an 10MHz unfortunately) on a old board, and I connected this one to the PIC.
I've enabled the PLL, so my PIC clocks at 8*4=32MHz.

On the oscilloscope, I get now a 2µs pulse, it's a little better.

[HenrikOlsson]

Now it seems to run properly - finally.

In order to make the calculations of the preload value match your new (32MHz) oscillator speed you need to change the Dummy2 value from 10000 to 8000.

Then keep the same test code in the interrupt service routine and try with InterruptFrequency = 10800, check the scope, there should now be pulses at 10800 or likely a little bit slower.

The reason it's not 10800 exactly is, again, due to time that the timer is actually stopped while reloading it. To tune it simply tweak the +1 in the following line:

TimerReload = 65535 - TimerReload + 1

Try +12 or something and see what happens.

Then try adding code to your interrupt, not all at once, add it in little by little and keep an eye on the scope. If you start to see jitter or "missed" pulses then you're "overloading" the PIC - ie interrupting to fast. Keep the code in the ISR as tight and short and possible. Think thru it, is there any other way to achive this or that to make this execute faster. Every cycle counts here. Verify with the scope, the pulsewidth shows the execution time of the ISR.

Trying to make a 3-phase inverter when you're new to PICs are quite a challange - as you probably/hopefully know by now - take baby steps.

[pxidr84]

Hurray, now I got something who works flawlessly.

I've played with the dummy values (Dummy2=8745 and Dummy3=100), now I get the exact sines I want.

For 1200 for example (120*10=120.0Hz), I get 120Hz, for 500 (50*10=50.0Hz) I get 50Hz, for 357 (35.7*10=35.7Hz) I get 35.7Hz...

So now it works, I can go ahead in my project.

Thanks a lot Henrik for your help and your support.

[HenrikOlsson]

Great!

I have no idea why you changed the Dummy2 and Dummy3 variables as you did (8750 and 100 (?) ) But then again, as long as it works for you....

Good luck with the rest of the project!