Using timer0

[mrfunkyjay]

Hi all, I have PIC18F1330.

It has two timer, namely timer0 and timer1. I have no problem with timer1. Here are my codes:

int GetPulse2(){
	T1CON=0b00000000;   /*Init timer1*/
	TMR1L=0;
	TMR1H=0;
	TRISAbits.TRISA1=1;   /*Make this pin as an input*/
	while(PORTAbits.RA1==1); /*Make pin low*/
	while(PORTAbits.RA1==0); /*While pin is high*/
	T1CONbits.TMR1ON=1;   /*Start timer1*/
	while(PORTAbits.RA1==1); /*When pin is low*/
	T1CONbits.TMR1ON=0;   /*Stop timer1*/
	return TMR1H*256+TMR1L;  /*return 16bit timer value*/
}

I have two Pulses. Namely Pulse1 and Pulse2. I need to use this microcontroller for sake of designing etc. I need to get my timer0 working at the same principal with the code above. Is it possible to do that with timer0? Or anyone has better idea/solution to this? Thank you very much.

PS: I am going to count the Pulse Width of PWM if this info useful.

 

[Nigel Goodwin]

Or anyone has better idea/solution to this? Thank you very much.

PS: I am going to count the Pulse Width of PWM if this info useful.

Try looking at the datasheet and series reference manual, look up the CCP module.

 

[mrfunkyjay]

there is no ccp module by the way, is there anything else?

 

[Nigel Goodwin]

there is no ccp module by the way, is there anything else?

That's a shame!.

Are you trying to read radio control pulses, or does it vary over a wider range than that?.

 

[mrfunkyjay]

yes radio control pulse from receiver module. it is between 1ms-1.5ms-2ms.

Do you have an idea? Timer is used to make resolution better, and I used it with timer1 before. Now I need another one with timer0. Is it possible? If not, why?

 

[Nigel Goodwin]

yes radio control pulse from receiver module. it is between 1ms-1.5ms-2ms.

Do you have an idea? Timer is used to make resolution better, and I used it with timer1 before. Now I need another one with timer0. Is it possible? If not, why?

You should be able to do it with timer0 if you want, or a simple software loop is all that's required, it's really a very simple thing to measure, as it's a nice fixed width variation.

I wouldn't get too excited about trying to get massive resolution, I don't think there's that much resolution in the original pulses.

 

[mrfunkyjay]

Check please...

Hi please check this for me, whether I made a mistake or not.

To count up to 2ms Pulse Width, I use 8bit timer/counter from timer0 (since PCB is made and timer1 is already used in this PIC18F1330).

-8bit timer0

-Prescaler of 8

-FOSC/4 = 1Mhz

-frequency input to timer0 would be 1Mhz/8 = 125kHz or T (period) = 8us

-since, 8 bit, 0-255 then overflow, 256x8us = 2.048ms which is enough and useable in this case.

CALCULATION:

2ms = (1/1Mhz) x 8 x ins.cycle

ins.cycle = 0.002s / 0.000008s = 250

RESULT:

250 decimal would be 2ms Pulse Width.

divide by two:

125 decimal would be 1ms Pulse Width.

center position of servo:

125/2 + 125 = 187.5 ~ 188.

then my code would be:

int GetPulse1(){
	T0CON=0b01000010;   /*Init timer0 8 bit, PSA assigned, 1:8 prescale value, reset timer0*/
	TMR0L=0;
	TMR0H=0;
	TRISAbits.TRISA0=1;   /*Make this pin as an input*/
	while(PORTAbits.RA0==1); /*Make pin low*/
	while(PORTAbits.RA0==0); /*While pin is high*/
	T0CONbits.TMR0ON=1;   /*Start timer0*/
	while(PORTAbits.RA0==1); /*When pin is low*/
	T0CONbits.TMR0ON=0;   /*Stop timer0*/
}

question is: will this work??

Later I will use 20 gap in between 188.

168 or less as turning left (servo)

169-207 as middle position

more than 208 as turning right.

Thanks for ur comments!!