Generate 40KHz without using pwm

[slaamdunk@gmail.com]

Are there ways to create a 40KHz square wave with 25% duty cycle without using PWM in pic 12F615, just by toggling the pins to '1' and '0'.
I tried and I am not getting an accurate frequency.
Thank You

 

[nagkiller]

Which compiler is used???
Try using 19us OFF and 6us ON!!! = 25us or 1/40000 = 0,000025s
If in c, use delay routine...

 

[slaamdunk@gmail.com]

Which compiler is used???
Try using 19us OFF and 6us ON!!!
If in c, use delay routine...

I am using Hi-Tech C. I am not getting an accurate frequency if I use the delay routine.
I theoretically calculated the time taken by each instruction using the clock frequency and I tried inserting delays to get a 25us ( 40KHz). But I am not getting the accurate frequency of 40KHz.

- - - Updated - - -

Which compiler is used???
Try using 19us OFF and 6us ON!!! = 25us or 1/40000 = 0,000025s
If in c, use delay routine...

#include    <htc.h>
//#include <PIC12F615.h>
#ifndef _XTAL_FREQ
#define _XTAL_FREQ 8000000
#endif


__CONFIG(IOSCFS_8MHZ & FOSC_INTOSCCLK & MCLRE_OFF & WDTE_OFF & PWRTE_OFF & CP_OFF & BOREN_OFF );



void main (){
int count = 96;
ANSEL=0x00;

GPIO=0;


TRISIO5 = 0x00;

while(1){
GPIObits.GP5=1; 
__delay_us(6);
GPIObits.GP5=0; 

__delay_us(19);


}

}

Is this how you were infering, because this is still not giving me an accurate 40KHz, it is somewhere near 36 - 37KHz.
Please let me know if I doing something wrong.
Thank you

 

[nagkiller]

Please... try this:

/* Hitech C using PIC12F629 */
#include <htc.h>

#ifndef _XTAL_FREQ
 #define _XTAL_FREQ 4000000
#endif

unsigned int count;

 __CONFIG ( FOSC_INTRCIO & WDTE_OFF & PWRTE_OFF & MCLRE_OFF & BOREN_OFF & CP_OFF & CPD_OFF );
void main()
{
	OSCCAL	= 0x3ff;
	GPIO	= 0x00;
	CMCON	= 0x07;
	TRISIO	= 0b00001000;
	GPIO= 0;
	while(1)
	{
		GPIO= 0xFF;		
		__delay_us(6);
		GPIO= 0;
		__delay_us(18);	
	}
}

I dont have oscilloscope!!! :-(

Here is 45KHz and 25% Duty in multimeter

 

[slaamdunk@gmail.com]

Please... try this:

/* Hitech C using PIC12F629 */
#include <htc.h>

#ifndef _XTAL_FREQ
 #define _XTAL_FREQ 4000000
#endif

unsigned int count;

 __CONFIG ( FOSC_INTRCIO & WDTE_OFF & PWRTE_OFF & MCLRE_OFF & BOREN_OFF & CP_OFF & CPD_OFF );
void main()
{
	OSCCAL	= 0x3ff;
	GPIO	= 0x00;
	CMCON	= 0x07;
	TRISIO	= 0b00001000;
	GPIO= 0;
	while(1)
	{
		GPIO= 0xFF;		
		__delay_us(6);
		GPIO= 0;
		__delay_us(19);	
	}
}

I dont have oscilloscope!!! :-(

Here is 45KHz and 25% Duty in multimeter

Why do you have an input in TRIS ? ( you have a 1 in that binary number )

 

[nagkiller]

Because in PIC12F629, The GPIO3 is only Input!!!
I like to use binary number in these registers...

Change to

		GPIO= 0xFF;		
		__delay_us(6);
		GPIO= 0;
		__delay_us(18);

 

[Simao.Berkof]

Running @ 4 MHz your machine cycle is 1 µs, so it´s not possible to achieve 6.25 µs (40 KHz @ 25% duty cycle).
If you need "exactly" 6.25 µs on and 18.75 µs off (40KHz @ 25%) you will have to choose among these clock
frequencies.

Xtal Freq........# machine cycles on.......# machine cycles off
MHz
1.280.........................2................................6
1.920.........................3................................9
2.560.........................4...............................12
3.200.........................5...............................15
3.840.........................6...............................18
4.480.........................7...............................21
5.120.........................8...............................24
5.760.........................9...............................27
6.400........................10..............................30
7.040........................11..............................33
7.680........................12..............................36
8.320........................13..............................39
8.960........................14..............................42
9.600........................15..............................45
10.240.......................16.............................48
10.880.......................17.............................51
11.520.......................18.............................54
12.160.......................19.............................57
12.800.......................20.............................60
13.440.......................21.............................63
14.080.......................22.............................66
14.720.......................23.............................69
15.360.......................24.............................72
16.000.......................25.............................75
.
.
.

This type of problem is a good example of those you get better results using assembly,

Below a possibility for a 16 MHz Xtal (thanks to PICLOOPS http://www.biltronix.com/picloops.html)

#asm

LOOP	movlw 0xff
	movwf GPIO
	movlw	D'7'
	movwf	CounterA
loopon	decfsz	CounterA,1
	goto	loopon
	nop
	movlw 0
	movwf GPIO
	movlw	D'23'
	movwf	CounterA
Loopoff	decfsz	CounterA,1
	goto	Loopoff
	nop		
	goto 	LOOP

#endasm

Because in PIC12F629, The GPIO3 is only Input!!!
I like to use binary number in these registers...

Change to

		GPIO= 0xFF;		
		__delay_us(6);
		GPIO= 0;
		__delay_us(18);