Thank you RobotFreak~~ This
Thank you RobotFreak~~ This is helping me and so as many others~
Thank you all. Hope this
Thank you all. Hope this tutorial is helpful for somebody.
Thank you so much for taking
Thank you so much for taking time and writing this!
Thank you so much about this
Thank you so much about this tutorial. (BOW)
Awesome tutorial!!
Man… I wish I saw this when I was trying to figure our timer interrupts! This explains it much better than anything else Ive seen online.
May I link / abstract this for the http://ArduinoInfo.Info WIKI?
Hi RobotFreak,
This is really good stuff, that is better than what I have right now on this subject.
May I link / abstract this for the http://ArduinoInfo.Info WIKI?
Regards, Terry King
…In The Woods in Vermont, USA
Hi Terry,thank you for
Hi Terry,
thank you for asking. Feel free to link / abstract to this tutorial
Regards Peter
Arduino Due Timer Interrupt
Do you know how to do that on the Arduino Due?
Nope
Sorry, I don’t know how to do that on the Due. It’s a different processor family. I own a Arduino Due, but I have tested only some examples.
Found this thread at Arduino forum: http://arduino.cc/forum/index.php?topic=130423.0
Thanks RobotfFreak!
Thanks for a great tutorial!
A question: can you (or anyone!) tell me what interrupts are used by the servo.h library in arduino? I’m working on a project that requires pwm controlled motors, servos and the use of a timer to program in a course for the bot to follow, and from my understanding the servo library uses timer1 while the pwm for the motors uses timer0 and timer2 (on arduino uno). Maybe if i know what interrupt the servo code is based on i can use another to time my programmed course?
Any tips greatly appreciated! Cheers.
Correct, Servo Lib is using
Correct, Servo Lib is using Timer1.
Example 3: Errors under Arduino 1.0x
Hi RobotFreak,
I show some of this on the http://ArduinoInfo.Info WIKI. The third example does not compile under Arduiono V1.04 - Problame with Wconstants.h - I fixed that but now also many problems with data typing… Any chance you could update that??
Thanks for your work on this. It’s a great explanation of a difficult subject.
Thanks for your reply
Thanks for your reply RobotFreak, can you tell me what interrupt servo uses? Is it the timer overflow, the compare a or b? I need to know which interrupts on timer1 are free to use.
Thanks
Hi Terry,the 3rd example has
Hi Terry,
the 3rd example has been updated to work with Arduino v1.x. Enjoy.
Sorry, I misunderstood your
Sorry, I misunderstood your question.
As yu can see in the servo.cpp source code, the servo lib is using the TIMER1_COMPA_vect interrupt source. But be warned, if you change the TCNT, or OCR registers the servo lib will be influenced.
MUCH More User-friendly than
MUCH More User-friendly than Oracle! Also a lot faster… Thanks!
Regards, Terry …In The Woods In Vermont
yes, he is sending two
yes, he is sending two months in future, using timing interrupt and jumping looop !
LOL
Damn, you’ve got me. Yes, I
Damn, you’ve got me. Yes, I confess, I have built a time machine. Greetings from the future.
BTW, The lottery numbers from 7/20/2013 are: 4 8 15 16 23 42
Thanks
This is awesome! Nice job on explaining these concepts.
What am I missing?
Essentially, I’ve started experimenting with timer interrupts with the goal of using the Arduino Uno Plus to control GE Color Effects lights, which are apparently fussy about timing. So, to start, I decided to try making a 20us time delay using an interrupt and basically copying your example and adding the clock pre-scaling table in the comments so I don’t have to keep looking it up.
Watching an LED blink for 20us is not informative :-), so I’ve swapped out the LED toggle line for setting a semaphore and reported the state of the semaphor back via the Serial monitor. I’ve introduced the variable “semaphore” because I ultimately want my main program to be able to tell if the 20us is up before moving on the the next instruction. The library I was originally working from uses delay() to do this and the author admits that it needs to be manually tuned for each arduino. I’ve tried this, and short of dragging out my old oscilloscope to verify the timing, it’s very hit-and-miss, so I thought I would turn to the timer driven interrupt method.:
===============================================
/Table 14-9.
Clock Select Bit Description from ATmega328P Documentation p.137
CS12 CS11 CS10 Description
0 0 0 No clock source (Timer/Counter stopped)
0 0 1 clk I/O /1 (No prescaling)
0 1 0 clk I/O /8 (From prescaler)
0 1 1 clk I/O /64 (From prescaler)
1 0 0 clk I/O /256 (From prescaler)
1 0 1 clk I/O /1024 (From prescaler)
1 1 0 External clock source on T0 pin. Clock on falling edge.
1 1 1 External clock source on T0 pin. Clock on rising edge.
Delays should be 10, 20 and 30us
10us = .000 01s which is obtained by dividing the 16MHz clock divided by 160
20us is therefore the 16Mhz clock divided by 80
30us is 16Mhz / 53
Therefore a good clock pre-scale setting would be 8 (CS11=1)
Timer will be running at 16Mhz/8 = 2Mhz or .5us per tick
Count to 20 for 10us
Count to 40 for 20us
Count to 60 for 30us
/
int semaphore=0;
void setup()
{
Serial.begin(115200);
pinMode(ledPin, OUTPUT);
Serial.println(“Semaphore cleared”);
// initialize timer1
noInterrupts(); // disable all interrupts
TCCR1A = 0;
TCCR1B = 0;
TCNT1 = 0;
OCR1A = 20; // compare match register for 10us delay
TCCR1B |= (1 << WGM12); // CTC mode
TCCR1B |= (1 << CS12); // 8 prescaler
TCCR1B |= (1 << CS10);
TIMSK1 |= (1 << OCIE1A); // enable timer compare interrupt
interrupts(); // enable all interrupts
}
ISR(TIMER1_COMPA_vect) // timer compare interrupt service routine
{
semaphore=1;
}
void loop()
{
while(semaphore==0){Serial.println(“semaphore = 0”);}
Serial.println(“Semaphore set”);
while (true){};
}
==================================================
This produces the output …
Semaphore cleared
semaphore = 0
semaphore = 0
semaphore = 0
semaphore = 0
semaphore = 0
Semaphore set
… which is what I would expect.
Obviously, since I’m really using the interrupt in place of a delay(), I don’t want to be constantly printing “semaphore = 0”, so I simply removed it. From here on I’ll focus only on the void loop() portion of the program. I’ve changed it to …
=============================================
void loop()
{
while(semaphore==0){}
Serial.println(“Semaphore set”);
while (true){};
}
=============================================
… but now all I get is:
Semaphore cleared
The semaphore is not being set, or at least, the main program isn’t seeing it.
I had thought that while(semaphore==0){} may not be valid with an empty proceedure, so I tested it …
========================================
void setup(){Serial.begin(115200);}
void loop(){
Serial.println(“before loop”);
while(true){}
Serial.println(“after loop”);
}
======================================
which only prints “before loop” so that wasn’t it.
So, back to original loop(). This also works …
======================================
void loop()
{
while(semaphore==0){delay(0);}
Serial.println(“Semaphore set”);
while (true){};
Serial.println(“not stuck in a loop”);
}
=====================================
but this does not …
…
while(semaphore==0){true==true;}
…
It occurs to me that both “delay(0);” and “Serial.println(”"); are using timers whereas {} and {true=true;} do not, so it’s possible that these functions is doing something with the timers that my code is not. This would imply that there’s something wrong with my setup() routine, but then again, the original example (which toggled the LED) worked, so clearly I’m not understanding something.
In fairness, I realize that putting delay(0); is not a hardship, but this is more about clarifying my understanding of why it doesn’t work without it than about saving instruction cycles.
LEGOManiac