Where communities thrive


  • Join over 1.5M+ people
  • Join over 100K+ communities
  • Free without limits
  • Create your own community
People
Repo info
Activity
Me No Dev
@me-no-dev
or Ticker
Michael Miller
@Makuna
@hagai-shatz how accurate do you need that 500us to be?
Hagai Shatz
@hagai-shatz
20% tolerance will be okay.
About 2000 executions per second.
@me-no-dev - but what if something else is handled in interrupt and it take time to finish? Does the AsyncServer is interrupt based?
Some SPIFFS calls takes >10ms to execute.
Me No Dev
@me-no-dev
@hagai-shatz using timer1 and it's regular ISR will not interrupt the network (that I have tested). Using NMI interrupt will, but I did not see any issues with that. I have not tested timer0 and Ticker, but Ticker should behave the same.
Hagai Shatz
@hagai-shatz
Can you point me to some examples please?
As for Ticker, I use it and it is not reliable even in 20ms intervals. It looks like when the ESP is busy with AsyncWebServer handlers it does not tick.
Me No Dev
@me-no-dev
analogWrite is an example with timer1, though it looks way more complicated than it is
gimme a minute to finish something and I'll try to put one up
Michael Miller
@Makuna
Same with the servo library, it uses both timer0 and timer1, but abstracts them thus making it look more complex than it is.
Me No Dev
@me-no-dev
@Makuna is ccompare running with higher prio than the network?
Michael Miller
@Makuna
Its been a year since I researched it and I have forgotten most of what I have learned; but I thought there was a way to set the level.
TIMERINT[0..NCCOMPARE-1]
Interrupt number for each comparator
Me No Dev
@me-no-dev
@hagai-shatz here is the code
Michael Miller
@Makuna
Its a strange interrupt, INTCLEAR doesn't work with it.
Me No Dev
@me-no-dev
#define TIMER_PERIOD 500 //us

void onTimer(){
  //do your thing
  // NO YIELD OR DELAY
}

void setup() {
  timer1_attachInterrupt(&onTimer);
  timer1_enable(TIM_DIV16, TIM_EDGE, TIM_LOOP);
  timer1_write(TIMER_PERIOD * 5);
}

void loop() {

}
@Makuna I digged myself a bit as well working on the ESP31B but forgot it all the same as you
Michael Miller
@Makuna
timer0 does not support scaling, it runs at instruction count speed always and doesn't auto reset. So you set the timer by calling timer0_write(count) giving it the instruction count to trigger on, once it fires you have to call write again to get it to fire again. To calculate the trigger count, call timer0_read() and add your count to it and pass this to write.
Me No Dev
@me-no-dev
count per microsecond depend on cpu speed and it's either 80 or 160
Michael Miller
@Makuna

Use something like this and avoid constants so you don't care about 80, 160.

    uint32_t usToTicks(uint32_t us) const
    {
        return (clockCyclesPerMicrosecond() * us);     // converts microseconds to tick
    }
    uint32_t ticksToUs(uint32_t ticks) const
    {
        return (ticks / clockCyclesPerMicrosecond()); // converts from ticks back to microseconds
    }

This is what the servo timer stuff uses when using timer0.

Me No Dev
@me-no-dev
static uint32_t ticksPeriod = 500;//still in us

void onTimer0(){
  uint32_t ticksAtEnter = timer0_read();
  //do your thing
  // NO YIELD OR DELAY
  timer0_write(ticksAtEnter + ticksPeriod);
}

void setup() {
  //convert period in us to ticks
  ticksPeriod *= clockCyclesPerMicrosecond();
  uint32_t ticksAtInit = timer0_read();
  timer0_attachInterrupt(&onTimer0);
  timer0_write(ticksAtInit + ticksPeriod);
}
@Makuna is this correct?
woops missed attachInterrupt
Hagai Shatz
@hagai-shatz
@Makuna, @me-no-dev - thanks for the examples, will give it a go.
Are there more differences between timer0 and timer1?
Can I break some other functionality by using them? For example, unable to use the servo library?
Me No Dev
@me-no-dev
above code does not run for timer0
I'm looking into why timer0_read is returning 0;
timer0 is used by the Servi lib
timer1 is used by analogWrite
so those will not work
Hagai Shatz
@hagai-shatz
Not good. But since I'm not planning on using Servi lib for now, this might be okay. As long as the timer0_read() works! :smile:
Me No Dev
@me-no-dev
ok I should have read @Makuna better and use ccount
also missed to init the interrupt
static uint32_t ticksPeriod = 500;//still in us

void onTimer0(){
  uint32_t ticksAtEnter = ESP.getCycleCount();
  //do your thing
  // NO YIELD OR DELAY
  timer0_write(ticksAtEnter + ticksPeriod);
}

void setup() {
  //convert period in us to ticks
  ticksPeriod *= clockCyclesPerMicrosecond();
  timer0_isr_init();
  timer0_attachInterrupt(&onTimer0);
  timer0_write(ESP.getCycleCount() + ticksPeriod);
}
both run with the same accuracy as far as I can tell
Hagai Shatz
@hagai-shatz
Thanks
Michael Miller
@Makuna
Last time I checked, timer0 was only used by servo library so in general it is open for use. Servo library can be told to use timer1 only also.
@me-no-dev esp.getcyclecount aND timer0_read should be the samething.
Me No Dev
@me-no-dev
@Makuna ccompare and ccount are not the same thing :)
Michael Miller
@Makuna
Sorry, my hands typed one thing and my mind was thinking something else, I meant they both use the same type, cycle counts.
Hagai Shatz
@hagai-shatz
Is there a similar interrupt I can setup on a specific pin? That is, instead of using timer, my ADC can set an external pin to high when data is ready to read (every 500us). How can I attach interrupt handler that will have good priority to ensure execution?
Me No Dev
@me-no-dev
use attachInterrupt(pin, fn, type);
Hagai Shatz
@hagai-shatz
Do I need to use attachInterrupt(digitalPinToInterrupt(pin), fn, type)?
Me No Dev
@me-no-dev
digitalPinToInterrupt no
pin and interrupt match here
Hagai Shatz
@hagai-shatz
Okay, thanks.
Ivan Grokhotkov
@igrr
regarding priority: the core inside esp8266 only has three interrupt levels. all "normal" interrupts are at level 1. Debug interrupt is level 2, and NMI is level 3.
so GPIO interrupt will not preempt other level 1 interrupts (e.g. timer interrupts)
Hagai Shatz
@hagai-shatz
@igrr , thanks for the clarifications.
Holger Lembke
@holgerlembke
so finally found some time to finish my flash check program for changing the flash chip.