Generate 40KHz without using pwm

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

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

nagkiller said:

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

Click to expand...

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.

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nagkiller said:

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

Click to expand...

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

Please... try this:


I dont have oscilloscope!!! :-(

Here is 45KHz and 25% Duty in multimeter

nagkiller said:

Please... try this:

Code:

/* 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

Click to expand...

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

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

Change to

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)

nagkiller said:

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

Change to

Code:

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

Click to expand...