Changing the sines frequency?

[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.