How to Set 20kHz PWM Frequency on PIC30F6010A With 16MHz Fosc in My Code?

45 6

#1 21664724 15 Nov 2012 06:21

Muniyasamy S Muniyasamy S

Anonymous

Post #1
21664724 15 Nov 2012 06:21

_FOSC(CSW_FSCM_OFF & XT_PLL8);
_FWDT(WDT_OFF);
_FBORPOR(PBOR_ON & MCLR_EN & PWRT_OFF);
_FGS(CODE_PROT_ON);

void Delay(unsigned int del);

int main(void)
{

Delay(50000);
TRISE=0x00;
PORTE=0x00;
PTCON=0x8004;
PTMR=100;
PTPER=199;
IPC9bits.PWMIP=1;
IFS2bits.PWMIF=0;
IEC2bits.PWMIE=1;
SEVTCMP=0x00;
PWMCON1=0xFFF;
PWMCON2=0x207;
DTCON1=0x4C4C;
DTCON2=0xFF;

FLTACON=0xFF80;
FLTBCON=0xFF80;
OVDCON=0xFF00;
PDC1=0x0A;
PDC2=6553.6;

while(1)
{
Delay(50000);
}
return (0);
}

void Delay(unsigned int del)
{
while(--del);
}

Hi friends this is my code for generating pwm pulses it is generating 275hz pulses but i want 20khz pulses there is no changes while changing PTPER value Same frequency only coming how to change frequency of pulses i am using 16Mhz PIC30F6010A controller please give me guidelines where to change the code for generating 20khz pulses thanks in advance
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#2 21664725 15 Nov 2012 07:05

Peter Evenhuis Peter Evenhuis

Anonymous

Post #2
21664725 15 Nov 2012 07:05

try to remove the two delay loops
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#3 21664726 15 Nov 2012 07:23

Muniyasamy S Muniyasamy S

Anonymous

Post #3
21664726 15 Nov 2012 07:23

Is delay loop is reason for frequency problem
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#4 21664727 15 Nov 2012 10:31

Syed Shadab Syed Shadab

Anonymous

Post #4
21664727 15 Nov 2012 10:31

Try mikroc for pic, this is a sample code,

void main()
{
TRISE=0x00;
while(1)
{
PORTE=0x00;
delay_us(50);
PORTE=0xFF;
delay_us(50);
}
}
This code will generate a square wave of 20KHz on PORTE, to check the exact time period observe the waveform on CRO and accordingly adjust the delay routine.
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#5 21664728 15 Nov 2012 10:41

Todd Hayden Todd Hayden

Anonymous

Post #5
21664728 15 Nov 2012 10:41

Where are you setting up the TMRx and PRx registers? The delay loops have nothing to do with your problem.

13.4.2 PWM PERIOD
The PWM period is specified by writing to the PRx
register. The PWM period can be calculated using
Equation 13-1.

EQUATION 13-1: PWM PERIOD
PWM Period = [(PRx) + 1] • 4 • TOSC •(TMRx Prescale Value)

PWM frequency is defined as 1/[PWM period].
#6 21664729 15 Nov 2012 12:17

Steve Lawson Steve Lawson

Anonymous

Post #6
21664729 15 Nov 2012 12:17

I took a look at the datasheet for that PIC (PIC30F6010A), which I have never used, but I noticed that there are two types of PWM module on this device:
* Simple PWM
* Motor control PWM

Motor control PWM has it's own time base, so if you are using that, perhaps you are not correctly configuring PTMR.

Sorry, I'm not familiar with the syntax in your sample code (I use MikroC which follows the datasheet naming conversion) and I'm unwilling to take the time to decipher it, thus the inquiry ;)

So, second question: Are you using the simple PWM or the motor control PWM?
#7 21664730 15 Nov 2012 13:15

Steve Lawson Steve Lawson

Anonymous

Post #7
21664730 15 Nov 2012 13:15

It occurred to me that I might be able to get a clue as to which PWM module you are using from your code, and judging by the fact that you are setting PTMR, that suggests that, either you are using the Motor Control PWM module (or you don't know what you are doing – no offense ;)

I see that you are setting PTMR to 100 and PTPER to 199. The reason the frequency isn't changing when you change the PTPER value is because it is greater than the PTMR value. This from the datasheet:

bq). The PTPER SFR sets the counting period for PTMR. The user must write a 15-bit value to PTPER. When the value in PTMR matches the value in PTPER, the time base will either reset to ‘0’, or reverse the count direction on the next occurring clock
cycle. The action taken depends on the operating mode of the time base.

In other words, the PTPER value must be less than the PTMR value, or it will never be reached because the timer will never count up that high.

Also, if you truly are trying to use the Motor Control PWM module, it is very complex so be sure to carefully read the datasheet.
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Topic summary

The discussion addresses generating a 20kHz PWM signal using a PIC30F6010A microcontroller with a 16MHz oscillator. The original code produces a low-frequency PWM (~275Hz) despite changes to the PTPER register. Key insights reveal that the PWM frequency depends on the PWM period register (PTPER) and the timer count register (PTMR), with the PWM period calculated as (PTPER + 1) × 4 × TOSC × prescale. The frequency remains unchanged because PTPER is set higher than PTMR, preventing the timer from reaching the period value. It is also clarified that the PIC30F6010A has two PWM modules: simple PWM and motor control PWM, with the latter using its own time base. Correct configuration of PTMR and PTPER is essential, ensuring PTPER is less than PTMR for proper PWM operation. Suggestions include removing delay loops (which do not affect PWM frequency) and using simpler code or tools like MikroC to generate a 20kHz square wave by toggling port pins with precise delays. The importance of understanding the specific PWM module in use and configuring its registers according to the datasheet is emphasized.
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How to Set 20kHz PWM Frequency on PIC30F6010A With 16MHz Fosc in My Code?

How to Set 20kHz PWM Frequency on PIC30F6010A With 16MHz Fosc in My Code?

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