How to set TMRO & TMR3 as Counter?.

[HenrikOlsson]

Hi,
I'm sorry but I'm not quite sure what the problem is...?

You can use TMR0 AND TMR1 as counters at the same time. OR you can use TMR0 AND TMR3 as counters at the same time. BUT you can NOT use TMR1 AND TMR3 as counters at the same time since they both share the same clock-pin (pin 15 on the 40-pin DIP package)

If this doesn't help please explain what the problem is , if you can.

/Henrik Olsson.

[NatureTech]

Hi Henrik,

Yes,that exactly i wanted to know ( you can NOT use TMR1 AND TMR3 as counters at the same time ).Ok,my doubt is cleared.Seems like i got to use an interrrupt pin and a counter.I hope it would work.And 1 more thing,the selection of QEI in PIC18F4431.If i don't want to use INDEX and wish to reset it using software (POSCNT=MAXCNT),am i have to set value of the maxcount ( Ex : MAXCNT = 1500 ) ??.And could i use single channel encoder output from 2 encoder which is from 2 different motor?.

I am sorry if i am bothering you alot,but this things is new to me and locally nobody had tried this kind of stuff due to the price of these electronics and availibility.

[HenrikOlsson]

Hi,

Ok,my doubt is cleared.Seems like i got to use an interrrupt pin and a counter.

Well, if you say so.... If you could explain what it is you're trying to do it may be easier for me or anyone else to suggest a solution. If you don't use TMR0 for anything you CAN use that AND TMR3, both as counters. If you ARE using TMR0 for something ELSE than a counter, perhaps you can shift that work to TMR3 thus making TMR0 and TMR1 available as counters - it all depends....

And 1 more thing,the selection of QEI in PIC18F4431.

I'm a bit confused...I thought we were talking about the 18F4550 here, the 18F4431 doesn't even have a TMR3.....

Regarding the QEI, if you don't want to use the Index channel you can either just let the position register overflow or use the position counter reset on period match. In the later case you set MAXCNT to the value at which you want the postion counter to reset to zero, 1500 for example.... You can NOT use just one channel from the encoder. The QEI module needs two channels, 90 degrees phase shifted with respec to each other. Otherwise it can't tell which way the motor is turning.

I am sorry if i am bothering you alot,but this things is new to me and locally nobody had tried this kind of stuff due to the price of these electronics and availibility.

No problem at all. That's what the forum is here for.

/Henrik Olsson.

[NatureTech]

Thanks Henrik.You understand my pain.

Well,what i am trying to do here is actually to have single channel encoder from each encoder (2 encoder) and feed it into PIC.I want to use interrupt but i belive when the interrupt occured,you got to clear it right?.Is this might lead to missing pulse as you have to loop to clear the interrupt?.Although without pause?.I even thought about using RB Port Change Interrupt as i belive i could hook up quadrature encoder to RB7:RB4 but i belive it could make some delay in clearing and again lead to missing pulse.

My apologise for confusing you with 18F4550 and 18F4431.I do own this chip and it's more awsome than LM629.

[ra68gi]

Hi nature tech,
Its been a long time since i last posted on this forum. I have written a program for a rotary encoder. But i have written it in C. I have used pic16f72 and have made 1x, 2x, 4x measurements. In 1x it increments counter only once for every pulse. I had used a 1000ppr(pulse per rev) encoder & the count value displayed on a LCD. So the resolution is 360degrees/1000. With 2x you will get double & with 4x you get 360/4000.
I have used different interrupt sources like portb int0, ccp,timer0, timer1.
If you are interested i will send you the source code.
The compiler Iam using is free version & you can write upto 2k code. And all this with instant interrupts.
If you are interested let me know & i will post it.

Raghunathan.

[mister_e]

Mikro C

[ra68gi]

No. It's BoostC.
If you are new to C & interested to learn it quickly, see this link..http://forum.sourceboost.com/index.php?showtopic=2399. C is more structured & universal language. I migrated to C recently & its power is awsome as regards to microcontroller programming. If you intend to impliment rtos on small ram pics, that too is available called nova rtos. Have a try.
Regards

Raghunathan.