Performing a loop every 10ms
Hello. I am not sure how to setup my PIC16F877A to run a looping section of my code every 10ms. A rate gyro must be read every 10ms consistently so that my integeration calculations don't go crazy. I've read the Timer0 section of the datasheet but I just don't understand it well enough to achieve what I want. I am using PIC Basic PRO.
If I have missed an important piece of information here please ask me for it.
Thankyou.
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needed
Can you display your code so that I will have an idea on what's going on.
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Hi, Wassup
As Timer 0 is a 8 bits timer ... and we suppose clock is 4Mhz ( ... )
I will be necessary to have a counting loop in the interrupt stub , because interrupts will occur every 256 µs as a maximum
The other solution is to use Timer 1 that has a 16 bits counting range ... and won't need any calculations.
Have a SEARCH for "PicMultiCalc" from Mr E. it's a nice tool to help for Timer designs ...
Alain
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Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
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IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
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??Originally Posted by Acetronics
Minimum?
Maximum?
I must be on the other side of the mirror.
"If the Earth were a single state, Istanbul would be its capital." Napoleon Bonaparte
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The other side of the Bosphor, certainly !!!
1x 1µs = 1µs ... 256x 1µs = 256µs ...
so, the maximum period is 256 µs ...
what was requested for, is a period duration of 10 ms ... or a 10,000 timer count !
Tell me if I'm wrong !!!
Alain
************************************************** ***********************
Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
************************************************** ***********************
IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
*****************************************
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Use an LED for initial testing, make blinky first, otherwise, I'll bet you'll drive yourself crazy trying to get it to work right.
One 'easy-ish' way to get it to work...
Set up timer 0 to interrupt on overflow, get an 'On Interrupt' stub to work blinking an LED. Change the Tmr0 prescaler to 1:64. You'll get an interrupt every 16.384ms instead of 10ms. Yes, it's a bit longer than what you want, but you can easily scale the results from the 16.384ms interrupt to make them look like the results from a 10ms interrupt.
16384/10000 = 1.6384.
No, PBP can't divide by a fractional number...but, you multiply it up by a large number and divide it back down by a whole number, keeping the ratio the same to keep the numbers correct...i.e.
16384/10000 = 1.6384 which is the same as
32768/20000 = 1.6384 which is the same as...and so on and so on...
Or, set up Tmr1 as a 16 bit timer that kicks off every 10ms...just like the other guys said...
But $20 says you're biggest problem will be understanding how to get the interrupt to work in the first place...
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Depends on what side you are standing at.
The "maximum" means fastest then.
Also, what do we get from TMR0 at 4Mhz at 1:4 prescaler ?
I get roughly 1.03ms.
I may be doing a wrong math here.
Last edited by sayzer; - 8th February 2008 at 19:11.
"If the Earth were a single state, Istanbul would be its capital." Napoleon Bonaparte
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Thankyou
Wow, thankyou for all of your replies.
I forgot to mention that my crystal is 20MHz and both CCP1 and CCP2 are being used for HPWM.
I found PicMultiCalc and it is saying that I can use the 8-bit timer (Timer0) for an error of 0.371%. It says that if I use the 16-bit timer I will get an error of 0%. Now I have decided that I will use the 16-bit timer only if it won't interupt my HPWM. The HPWM is driving two motors. I am not at all familure with these timers and I don't know how to set them up or know when to start my 10ms loop so that the gyro can be read at the start of every loop at 100Hz (10ms intervals). Integration calculations and other processes are carried out after the gyro has been read. If all calculations and procesess have been done before the next loop should start, the processor should wait until the timer flag or whatever signals the loop to start over.
FYI I am making a balancing robot.
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Said it before, I'll say it again...
Start simple...
Get the LED blinking at a known rate under an interrupt drive (or just get an LED blinking), get the HPWM working on all channels in all situations, get the interfaces working, THEN tie them all together.
Otherwise you'll be shooting yourself in the foot wondering why...no more...just wondering WHY!!!!
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Well ok; so it's just a trial and error thing then? I'll just experiment with the PICMULTICALC values by plugging them into the right registers and i'll see how I go. BTW I have no idea of how to use an interupt. Anyhelp in using interupts in PBP relating to what I need will be very much appriciated.
I was hoping someone here has done what I want done before. Or perhaps someone could link me somewhere, but thanks for all of your help.
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The old 'inverted pendulum' trick has been done a lot by various people using various processors...but in the end, it's all up to the guy behind the keyboard.
Read the book, work your way up to it...otherwise, again, your foot will end up with holes in it...
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You should browse the parallax site ...
They already did it ( and they share it !!! ) ... and moreover their basic is PbP compatible !!!
... at least TONS of understandable solutions to your headaches ...
Alain
************************************************** ***********************
Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
************************************************** ***********************
IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
*****************************************
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I saw that balancing robot on the paralax website. It doesn't use a gyro and an accelerometer. Useless on a sloped surface.
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Differential GPS, one on each corner of a 4 cornered base... Solves everything!
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Ok I got the timer going, but brace yourself for a possible kalman filter question. I havn't found a single website that can explain kalman filters in laymens terms.
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... ROFL !!
THEY show you how to interface with the sensors, YOU write the program for your own requirements and dreams, with YOUR sensors.
Not just a cut and paste party ...
Alain
************************************************** ***********************
Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
************************************************** ***********************
IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
*****************************************
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And you probably won't find one.
Best explanation I can offer is that a Kalman filter makes a best 'future guess' based on the accuracy of it's past 'future guesses'.
If the Kalman filter isn't sure of itself, it's 'future guess' goes out the window.
I remember this from working the INU's on -130's. Ring Laser Gyro based INU's. The aircrews wouldn't believe the INU's position, so they'd update the things fairly often from TACAN or RADAR or whatever, even handheld GPS's. Then they'd whine when they got back because the INU would start drifting really badly inflight. The crews would come back and whine, we'd explain to them that they had ruined the INU's confidence by telling the INU it wasn't where it thought it was even though the difference between where the INU thought it was and where the crew told it that it was was very small. But of course, the aircrews knew better, because they're officers, and have degrees right?
We'd have to go out and run a ground align on the INU about a half a dozen times and each time, just let the INU cook by itself for awhile to build up it's confidence. At first it would sit there and drift away from the spot the aircraft was on. After a couple of time, the drifting would get less and less and eventually, it wouldn't drift at all.
But all that explanation doesn't help a person write any code now does it?
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This post above and the post about the PicMultiCalc have been the most usefull to me in this thread. PicMultiCalc taught me a little bit of how timer0 works, and the post above taught me in laymens terms what the kalman filter does. The post two poitions up by Acetronics is not usefull and this person has probably no life. (:
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Well, then let me not help you out a bit more...
If I could edit my Kalman filter post down to nothing but agreement with post #16, I would, but I can't.
And a Kalman filter is a helluva lot more complicated than the 'layman's terms' I laid out...and probably beyond your level of comprehension by a few orders of magnitude...
So, when you get a chance, here's what you do....
Step outside and go play a one handed game of hide and go #@$^&^@ yourself...
Last edited by skimask; - 13th February 2008 at 05:14.
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East Tonto, You got leftover DoNuts older than this Kid . . .But ... LMAO
Last edited by Archangel; - 13th February 2008 at 20:42.
If you do not believe in MAGIC, Consider how currency has value simply by printing it, and is then traded for real assets.
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Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants - but debt is the money of slaves
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There simply is no "Happy Spam" If you do it you will disappear from this forum.
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East Tonto? Huh? Where am I? Too rough?
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The Caïman Filter,the one that bites ...
If that page doesn't give you enough to understand those filters ...
http://www.cs.unc.edu/~welch/kalman/
There's no more to do for you than sell hotdogs, bretzels or pizzas ( even donuts ) in the street ...
I also remember having seen some of these filters used in UAV's ...
So, I suspect more a SEARCHing problem than an Understanding problem ...
But it's me ...
Alain
************************************************** ***********************
Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
************************************************** ***********************
IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
*****************************************
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Hi Alain,
I looked at the whitepaper on that website . . . is that really math or pop art?
You wanna buy a hot dog?
If you do not believe in MAGIC, Consider how currency has value simply by printing it, and is then traded for real assets.
.
Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants - but debt is the money of slaves
.
There simply is no "Happy Spam" If you do it you will disappear from this forum.
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Hi, Joe
Was somewhat like that when I first discovered Fuzzy Logic ...
You know what ???
I DO HATE Maths ... But will surely enjoy a good Hotdog !!! _ Making Hoddogs is a full job. Programming Pic too.
LOL !!!
Alain
Last edited by Acetronics2; - 14th February 2008 at 10:30.
************************************************** ***********************
Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
************************************************** ***********************
IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
*****************************************
|
What a group of people. This forum is sad. It seems like we have a serious case of arrogant and negatively biased people. It's sad that such a potentially useful topic had to end like this. I only wanted some simple help and it seems some people have different reasons for being here. Whether it be belittleing people or actually giving them a hand in solving a problem. I certainly won't be recommending people come here. I certainly hope you idiots stick to this corner of the website and don't infect anywhere else. I've never encountered such a negative group of people like this on any other forum. Well done. ):
For those people who know they did no wrong, are not responsible.
I hope the site admin read this.
Last edited by wasssup1990; - 14th February 2008 at 09:40. Reason: grammer
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Whatever happened to people that want to learn.. Seems like all anyone wants these days is their problems solved for them with as little effort as possible on their part.
That is what is really sad.
Here we have a group of people willing to help others in a fairly complicated field, for no compensation whatsoever. From all walks of life and technical backgrounds, willing to share their knowledge.
I do hope that people like wasssup will wise up. If they do not, and more of the world is filled with people like that... I fear for the future.
Dave
Always wear safety glasses while programming.
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You're in the minority that thinks this way.
Useful to...YOU. If it wasn't useful to...YOU...then you wouldn't be whining.It's sad that such a potentially useful topic had to end like this.
You wanted it handed to you on a platter so you could modify it and call it your own and impress your teachers or your buddies...whatever...I only wanted some simple help and it seems some people have different reasons for being here.
If you couldn't figure this out, what makes you think your recommendations will hold any water in the first place?Whether it be belittleing people or actually giving them a hand in solving a problem. I certainly won't be recommending people come here.
Negative, maybe...but if it'll trip you off into trying to make your own solutions work rather than getting somebody else to do it, then you're probably better off in the long run...ya think?I certainly hope you idiots stick to this corner of the website and don't infect anywhere else. I've never encountered such a negative group of people like this on any other forum. Well done. ):
Probably will, might laugh, might cry...you think they read everything? Probably do...not a LOT of traffic here to filter thru.I hope the site admin read this.
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I had a guy in my shop this morning, 32 years old, and I thought he was a smart guy, messes with electronics, etc.etc. Had a flat tire and didn't know how to change it so he called a tow truck. $200USD for the call!!! And he was here at the shop. He could've walked 15 feet and asked me to help him out...
That's the kind of crap the world is facing sooner more than later...
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That fellow could have been just plain LAZY. Either way, he has a problem.
Does this all boil down to the way kids are raised now days?
Dave
Always wear safety glasses while programming.
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I don't think so... I acted up, my parents/relatives/adult around the block/etc, they all let me know it up-side the head.
Might be the way those morons in 'high places' on their high-horses are telling us we have to raise kids nowadays...
Remember getting slapped up-side the head in the grocery store by Mom 'cause you were messing around? Try and do that these days... Amazing how much a guy CAN'T get away with these days...
Oh....you're talking about the guy in my shop!!!
Ya, I've just figured out he's an idiot and/or Lazy...
So we're all rubbing it in that the guy can't change a flat tire...and we'll probably continue to do so for another few weeks/months. (BTW - I took a look at his vehicle, the instructions, with pictures, are right there in his owner's manual in the glove box and a picture diagram in plain view on the trunk lid (boot cover?)...this guy is now in my book as useless...)
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When I was growing up and Mom said that she was getting a SWITCH...She was not referring to an electrical component
Dave
Always wear safety glasses while programming.
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Ya, mine too...it think it was an OKMU switch...One kid, multiple uses...for some reason, I begin to think that I was always the one that turned that switch on........and it seems like it never turned off!When I was growing up and Mom said that she was getting a SWITCH...She was not referring to an electrical component
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There you go people, my point has been backed up by these last few replies. I notice there are alot of assumptions being made.
E.g. 1 From skimask: "You wanted it handed to you on a platter so you could modify it and call it your own and impress your teachers or your buddies...whatever..."
Now that is some assumption. You jumped to that conclusion skimask, I know some other people on this form may do that, but all I needed was a somewhere to start. Go and look at my first post. See how innocent that looks? I guess the assumptions started right there. (:
E.g. 2 From mackrackit: "Whatever happened to people that want to learn.. Seems like all anyone wants these days is their problems solved for them with as little effort as possible on their part."
This person made the same assumption. What made you think I just wanted the answer straight up? It would have helped if someone could step me through how to set up Timer0.
Acetronics thought this was a cut and paste party. All I needed was some guidance.
Hmm I wonder what's going to be said next?
Last edited by wasssup1990; - 15th February 2008 at 03:20.
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Allow me.... ('cause most will
Post #1 = +
Post #2 = +
and so on...
Post #15 = +
Post #16 = +
Post #17 = NEGATIVE - and it'll all downhill from there...thanks to...anyone...anyone...yep, you guessed it...
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It's suppoased to be a loop every 10ms.
Not an insult every 10 ms.
It's like a "Pack of Wolves".
And wasssup didn't start anything.
Y'all need to mellow out, and write some code.
Here's mine...
HTH,Code:ReadingTaken VAR BIT TRM0IF VAR INTCON.2 TMR0IE VAR INTCON.5 TimerReload CON 60 OPTION_REG = %11010111 ; Assign Prescaler to TMR0, 1:256, internal clock TMR0 = TimerReload ; Load timer for first delay TMR0IF = 0 ; Clear the interrupt flag ReadingTaken = 0 ; indicate reading hasn't been taken yet TMR0IE = 1 ; Enable TMR0 interrupt ON INTERRUPT GOTO TakeReading Main: If ReadingTaken then ; Wait for reading to be taken ReadingTaken = 0 ; Indicate the reading has been handled ; -- Reading has been taken, do something with it here -- endif GOTO Main DISABLE TakeReading: TMR0 = TimerReload ; reload timer for next period TMR0IF = 0 ; Clear the interrupt flag ; -- this is called every ~10.036ms -- (with 20mhz OSC) ; Take your reading ReadingTaken = 1 ; Tell main loop that a reading has been taken RESUME ENABLE
DT
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Thankyou Darrel
Admin has come to the rescue.
Thankyou for that usefull code. If I ever use any of it I will put credit to you in my source code and whoever else you think deserves credit for it.
I hope I never run into trouble like this again on this forum. I'm just a electronics and programming hobbiest needing a little programming help. I didn't need any of that rubbish above.
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MHhhhhh,
Thinking to it, Darrel is perfectly right ... ( as most of time ! )
We are here for programming pics tricks ... and Everything else is just "optionnal". May be this thought could avoid further fighting parties ...
Here are My two cents !
Alain
************************************************** ***********************
Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
************************************************** ***********************
IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
*****************************************
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Minor correction to DT's code above:
TRM0IF VAR INTCON.2 should be TMR0IF VAR INTCON.2
Also, I agree with DT. Here is my code thingie with my approach:
1.03mS interrupt at 4 MHz, 1:4 Prescaler Assigned to TMR0.
This works the opposite way of what DT does.
DT's code interrupts every 10mS, my code interrupts every 1mS.
Work on either one.
Code:<font color="#008000">@ DEVICE PIC16F628A, INTRC_OSC_NOCLKOUT, WDT_OFF, PWRT_OFF, MCLR_OFF,PROTECT_ON,CPD_ON, BOD_OFF </font>SetAll: <font color="#000080"><b>CLEAR </b></font>TRISA = <font color="#FF0000"><b>%00000000 </b></font>TRISB = <font color="#FF0000"><b>%00000000 </b></font>CMCON = <font color="#FF0000"><b>7 </b></font>VRCON.<font color="#FF0000"><b>7 </b></font>= <font color="#FF0000"><b>0 </b></font>VRCON.<font color="#FF0000"><b>6 </b></font>= <font color="#FF0000"><b>0 </b></font>PORTA = <font color="#FF0000"><b>0 </b></font>PORTB = <font color="#FF0000"><b>0 </b></font>TimeAdder <font color="#000080"><b>VAR BYTE </b></font>OPTION_REG.<font color="#FF0000"><b>5 </b></font>= <font color="#FF0000"><b>0 </b></font><font color="#000080"><i>' TMR0 internal clk select bit. </i></font>OPTION_REG.<font color="#FF0000"><b>3 </b></font>= <font color="#FF0000"><b>0 </b></font><font color="#000080"><i>' Prescaler Assigned to TMR0. </i></font>OPTION_REG.<font color="#FF0000"><b>2 </b></font>= <font color="#FF0000"><b>0 </b></font><font color="#000080"><i>' Bit 2,1,0 : 1:4 prescaler. </i></font>OPTION_REG.<font color="#FF0000"><b>1 </b></font>= <font color="#FF0000"><b>0 </b></font>OPTION_REG.<font color="#FF0000"><b>0 </b></font>= <font color="#FF0000"><b>1 </b></font>T0IE <font color="#000080"><b>VAR </b></font>INTCON.<font color="#FF0000"><b>5 </b></font><font color="#000080"><i>'INTCON.5 = 1 ' Enable TMR0 interrupt. </i></font>T0IF <font color="#000080"><b>VAR </b></font>INTCON.<font color="#FF0000"><b>2 </b></font><font color="#000080"><i>'INTCON.2 = 0 ' TMR0 interrupt overflow bit. Must be cleared in software. </i></font>T0IF = <font color="#FF0000"><b>0 </b></font><font color="#000080"><i>' Cleared. </i></font>T0IE = <font color="#FF0000"><b>1 </b></font><font color="#000080"><i>' Enable TMR0 interrupt. </i><b>ON INTERRUPT GOTO </b></font>TMR0_Int Begin: <font color="#000080"><b>IF </b></font>TimeAdder = <font color="#FF0000"><b>10 </b></font><font color="#000080"><b>THEN </b><i>' We have 10mS cycle. </i></font>TimeAdder = <font color="#FF0000"><b>0 </b></font><font color="#000080"><i>' Clear time adder. 'Do something here. '. '.. '... </i><b>ENDIF GOTO </b></font>Begin <font color="#000080"><b>DISABLE </b></font>TMR0_Int: <font color="#000080"><i>'This routine is called every 1.03mS. Act Fast here. </i></font>TimeAdder = TimeAdder + <font color="#FF0000"><b>1 </b></font>T0IF = <font color="#FF0000"><b>0 </b></font><font color="#000080"><i>' Clear interrupt flag bit. </i><b>RESUME ENABLE </b></font>
"If the Earth were a single state, Istanbul would be its capital." Napoleon Bonaparte
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WooHoo!, Somebody's paying attention. I love it!
Dang dyslexia.
Thanks Sayzer!
<br>
DT
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Attention is in my heart,
Reading and posting is never hard,
Let be friends, don't post assault,
Share the knowledge, you won't lose a byte.
P.S. - I am in finals going toward award.
"If the Earth were a single state, Istanbul would be its capital." Napoleon Bonaparte
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