HPWM10 Frequency Updating

[duncan303]

Hi

This week I are been mostly working on HWPM.......... to produce undetermined fixed frequencies on CCP1 between approx 10,000Hz and 500,000Hz for durations of approx 10 seconds. For the moment the dutycycle is a secondary consideration. I am testing using a 16f628A at the moment but I may have to change to an 18 series. It must use HPWM

As this is a broad range and to achieve better resolution at the higher frequencies I am running at 16mhz and introducing prescaling at the lower frequencies.

The frequency required is received HSER as a WORD and the code calculates PR2 etc. My own code sort of works Ok but it is very ugly and limited ( I upgraded to 2.5 to use LONGS etc but have yet to been unable to get PBL to compile with anything significant )


However,

I have also had an constant eye on HPWM10 By Darrell Taylor (Peu and Mister E whose Pic multi-Calc I use as de facto: thankyou Mister E) considering that I may have certain frequency ranges dedicated to different channels.

HPWM10 works beautifully to update the dutycycle of given frequencies, smooth and glitch free and very easy to use. However I would be using it the other way round ie to update the frequency for a given dutycycle. Given the fact that 10Bit resolution is not always available over the ranges I am working with, I set the variable _DutyCycle = 100.

There are stages in my frequency range when the BYTE value of PR2 overflows and the prescaler is incremented. For the purpose of this post I have the prescaler set 1:1

A bit long winded but I have captured the value of PR2 with respect to frequency as output from HPWM10 and inconsistencies start to occur around 35940Hz , PR2 recovers at 36140Hz but as can be seen in capture1.txt the trend occurs more regularly thereafter. The inconsistencies are as compared to Mister E's Pic multi-Calc.

I should be able to work out why this is happening rather than just observing, however I am confused......... could this be to do with parsing during the maths calculation?

Duncan

[Charles Linquis]

I don't know if it will help you, but some time ago I wrote a little routine for an 18F8722 running at either 20 or 40Mhz that lets you enter the PWM frequency and then increment and decrement the duty cycle with the UP and DOWN arrow keys on a keyboard.

It doensn't allow for infinite frequencies, but is a good test tool.

<CODE>

HSEROUT [13,10,10,"1. Test PWM ",13,10]



HSEROUT [13,REP 10\4]
HSEROUT ["Pick PWM Frequency 1 = 312Khz,2 = 156Khz, 3 = 78Khz, 4 = 39Khz "]
HSERin [Char]
IF Char < "1" or Char > "4" THEN
HSEROUT [13,10,10]
GOTO SpecialUse
ENDIF

IF Mhz40 = 1 THEN
Select CASE Char

CASE "1"
PWMFREQ = $1F
NumBits = 7
MaxPWM = 127

CASE "2"
PWMFREQ = $3F
NumBits = 8
MaxPWM = 255

CASE "3"
PWMFREQ = $7F
NumBits = 9
MaxPWM = 511

CASE "4"
PWMFREQ = $FF
NumBits = 10
MaxPWM = 1023
END SELECT

ELSE
Select CASE Char

CASE "1"
PWMFREQ = $F
NumBits = 6
MaxPWM = 63

CASE "2"
PWMFREQ = $1F
NumBits = 7
MaxPWM = 127

CASE "3"
PWMFREQ = $3F
NumBits = 8
MaxPWM = 255

CASE "4"
PWMFREQ = $7F
NumBits = 9
maxPWM = 511
END SELECT
ENDIF


CCP1CON = %00001100
CCPR1L = %00010000
CCPR1H = %00000000 ' Initialize to 0, PWM register
PR2 = PWMFREQ
T2CON = %00000100 ' Prescale 1, Timer2 ON - Needed for PWM
PORTC.2 = 0
TRISC.2 = 0
PWMVal = 0
Gosub WritePWMreg
HSEROUT [13,10,10]

HSEROUT ["PWM Value (",#MaxPWM," Max)",13,10]
HSEROUT ["0",8]
NewChar:
HSERIN [Char]
If Char = 27 THEN
HSERIN 50,NoArrow,[Char2,Char3]
IF Char3 = 65 AND PWMVal < MaxPWM tHEN
PwmVal = PWMVal + 1
ENDIF
IF Char3 = 66 AND PWMVal > 0 tHEN
PwmVal = PWMVal - 1
ENDIF
HSEROUT [#PWMVal," ",REP 8\7]
GOSUB WritePWMReg
ENDIF

goto NewChar
NoArrow:
Break = 1
PWMVal = 0
Gosub WritePWMReg
CCP1CON = 0 ; Shut off the PWM controller
GOTO Begin



WritePWMReg:
CCPR1L = PWMVal >> 2
CCP1CON.5=PWMVal.1
CCP1CON.4=PWMVal.0
RETURN

</CODE>

[Darrel Taylor]

Hi Duncan,

I'm not sure how you're getting frequencies between 10,000 and 500,000 in a word var, but for sure, the HPWM10 macro will have problems with frequencies greater than 32,767.

The calculation from frequency to TimerTicks uses the DIV32 command, and the Divisor has a 15-bit maximum (32,767). The limitation is the same for PBP's HPWM.

Since you have PBPL, it's possible to modify the macro to use LONG's.
Then it won't have the DIV32 problem anymore.

But if you're having problems getting PBPL to work. That may not help out either.
<br>

[BrianT]

I need a ten bit HPWM so I searched for "HPWM10 macro" as mentioned in the prior post.

No joy.

Here is the error message.........

Did you mean: HPM 10 macro

No standard web pages containing all your search terms were found.

Your search - HPWM10 macro - did not match any documents.

Suggestions:
Make sure all words are spelled correctly.
Try different keywords.
Try more general keywords.
Try fewer keywords..........

Where can I find a 10 bit HPWM command?

Cheers
BrianT

[Darrel Taylor]

I'd like to be able to explain the search engines..... but I can't.

Good thing there's People around.

https://www.picbasic.co.uk/forum/showthread.php?p=37805
<br>

[Charles Linquis]

The code that I posted does a 10bit HPWM.

[Darrel Taylor]

The code that I posted does a 10bit HPWM.

Glitch Free to 500khz ?

Yeah, mine neither.
<br>