delayMicroseconds() - crash

[Gorkde]

ESP12F

I'm working on a PWM Routine (not finished still in progress) which did crash for some reason (code#1).

Then I assumed it's too fast so I added delay(1) in the loop and no crash occured anymore (code#2).

Then I thought to make the delay smaller so I changed delay(1) to delayMicroseconds(100) and it did crash again.

So I changed delayMicroseconds(100) to delayMicroseconds(1000) which should be the same as delay(1) which didnt crash. But it does crash again with that! (code#3).

Code 1:

#include <ShiftRegister74HC595.h>

ShiftRegister74HC595 ShiftRegOut (1, 2, 4, 5); // Schieberegister Objekt erstellen (Anz. Register, Datenpin, Schiebetaktpin, Speichertaktpin (latch-pin)

void setup()
{
  Serial.begin(115200);
  ShiftRegOut.setAllLow();
}

void loop()
{
  FadeOutput(2, 0, 255, 4.16);
  delay(500);
  /*  FadeOutput(2, 255, 0, 1);
    delay(500);*/
}

int FadeOutput(int Pin, int StartWert, int EndWert, float Zeit)                                                 // Bei Fade 0-255 max. 4.195 Sek möglich
{
  if (StartWert < 0 || StartWert > 255 || EndWert < 0 || EndWert > 255 || StartWert == EndWert || Zeit > 4.195)  // Bei falscher Parameterübergabe Fehler zurückmelden
  {
    return (-1);
    Serial.print("ERROR!");
  }

  if (StartWert < EndWert)
  {
    long MillisZeit = millis();

    float Freq = (EndWert - StartWert) / Zeit;
    long Zyklus = 1000000 / Freq;

    Serial.print("Freq: ");
    Serial.println(Freq);
    Serial.print("Zykluslaenge[Microsecs]: ");
    Serial.println(Zyklus);

    for (int i = StartWert; i <= EndWert; i++)
    {
      PWMOutput(Pin, i, Freq);
      // NO DELAY HERE
    }

    MillisZeit = millis() - MillisZeit;
    Serial.print("Fade-Zeit[ms]: ");
    Serial.println(MillisZeit);
    Serial.print("\n");
  }
  /*
    else if (StartWert > EndWert)
    {
      for (int i = StartWert; i >= EndWert; i--)
      {
        PWMOutput(Pin, i, 300);
      }
    }
  */
}

void PWMOutput(int Pin, int PWM_Wert, float PWM_Freq)   // PWM_Wert 0-255 - Freq >61Hz sonst Probleme wegen max. Millis() Länge.
{
  long Zykluslaenge = 1000000 / PWM_Freq;
  float ProzentAN = PWM_Wert / 255.0;
  int AN_Zeit = ProzentAN * Zykluslaenge;
  int AUS_Zeit = Zykluslaenge - AN_Zeit;
  Serial.print("PWM_Freq ");
  Serial.println(PWM_Freq);
  Serial.print("PWM_Wert ");
  Serial.println(PWM_Wert);
  Serial.print("Zykluslaenge ");
  Serial.println(Zykluslaenge);
  Serial.print("ProzentAN ");
  Serial.println(ProzentAN);
  Serial.print("ON Time ");
  Serial.println(AN_Zeit);
  Serial.print("OFF Time ");
  Serial.println(AUS_Zeit);
  Serial.print("\n");

  if (AN_Zeit > 0)
  {
    ShiftRegOut.set(Pin, HIGH);
    delayMicroseconds(AN_Zeit);
  }
  ShiftRegOut.set(Pin, LOW);
  delayMicroseconds(AUS_Zeit);
}

Code 2:

#include <ShiftRegister74HC595.h>

ShiftRegister74HC595 ShiftRegOut (1, 2, 4, 5); // Schieberegister Objekt erstellen (Anz. Register, Datenpin, Schiebetaktpin, Speichertaktpin (latch-pin)

void setup()
{
  Serial.begin(115200);
  ShiftRegOut.setAllLow();
}

void loop()
{
  FadeOutput(2, 0, 255, 4.16);
  delay(500);
  /*  FadeOutput(2, 255, 0, 1);
    delay(500);*/
}

int FadeOutput(int Pin, int StartWert, int EndWert, float Zeit)                                                 // Bei Fade 0-255 max. 4.195 Sek möglich
{
  if (StartWert < 0 || StartWert > 255 || EndWert < 0 || EndWert > 255 || StartWert == EndWert || Zeit > 4.195)  // Bei falscher Parameterübergabe Fehler zurückmelden
  {
    return (-1);
    Serial.print("ERROR!");
  }

  if (StartWert < EndWert)
  {
    long MillisZeit = millis();

    float Freq = (EndWert - StartWert) / Zeit;
    long Zyklus = 1000000 / Freq;

    Serial.print("Freq: ");
    Serial.println(Freq);
    Serial.print("Zykluslaenge[Microsecs]: ");
    Serial.println(Zyklus);

    for (int i = StartWert; i <= EndWert; i++)
    {
      PWMOutput(Pin, i, Freq);
      delay(1);          // THIS DOESN'T CRASH FOR ME!
    }

    MillisZeit = millis() - MillisZeit;
    Serial.print("Fade-Zeit[ms]: ");
    Serial.println(MillisZeit);
    Serial.print("\n");
  }
  /*
    else if (StartWert > EndWert)
    {
      for (int i = StartWert; i >= EndWert; i--)
      {
        PWMOutput(Pin, i, 300);
      }
    }
  */
}

void PWMOutput(int Pin, int PWM_Wert, float PWM_Freq)   // PWM_Wert 0-255 - Freq >61Hz sonst Probleme wegen max. Millis() Länge.
{
  long Zykluslaenge = 1000000 / PWM_Freq;
  float ProzentAN = PWM_Wert / 255.0;
  int AN_Zeit = ProzentAN * Zykluslaenge;
  int AUS_Zeit = Zykluslaenge - AN_Zeit;
  Serial.print("PWM_Freq ");
  Serial.println(PWM_Freq);
  Serial.print("PWM_Wert ");
  Serial.println(PWM_Wert);
  Serial.print("Zykluslaenge ");
  Serial.println(Zykluslaenge);
  Serial.print("ProzentAN ");
  Serial.println(ProzentAN);
  Serial.print("ON Time ");
  Serial.println(AN_Zeit);
  Serial.print("OFF Time ");
  Serial.println(AUS_Zeit);
  Serial.print("\n");

  if (AN_Zeit > 0)
  {
    ShiftRegOut.set(Pin, HIGH);
    delayMicroseconds(AN_Zeit);
  }
  ShiftRegOut.set(Pin, LOW);
  delayMicroseconds(AUS_Zeit);
}

Code 3:

#include <ShiftRegister74HC595.h>

ShiftRegister74HC595 ShiftRegOut (1, 2, 4, 5); // Schieberegister Objekt erstellen (Anz. Register, Datenpin, Schiebetaktpin, Speichertaktpin (latch-pin)

void setup()
{
  Serial.begin(115200);
  ShiftRegOut.setAllLow();
}

void loop()
{
  FadeOutput(2, 0, 255, 4.16);
  delay(500);
  /*  FadeOutput(2, 255, 0, 1);
    delay(500);*/
}

int FadeOutput(int Pin, int StartWert, int EndWert, float Zeit)                                                 // Bei Fade 0-255 max. 4.195 Sek möglich
{
  if (StartWert < 0 || StartWert > 255 || EndWert < 0 || EndWert > 255 || StartWert == EndWert || Zeit > 4.195)  // Bei falscher Parameterübergabe Fehler zurückmelden
  {
    return (-1);
    Serial.print("ERROR!");
  }

  if (StartWert < EndWert)
  {
    long MillisZeit = millis();

    float Freq = (EndWert - StartWert) / Zeit;
    long Zyklus = 1000000 / Freq;

    Serial.print("Freq: ");
    Serial.println(Freq);
    Serial.print("Zykluslaenge[Microsecs]: ");
    Serial.println(Zyklus);

    for (int i = StartWert; i <= EndWert; i++)
    {
      PWMOutput(Pin, i, Freq);
      delayMicroseconds(1000);          // THIS DOES CRASH TOO!
    }

    MillisZeit = millis() - MillisZeit;
    Serial.print("Fade-Zeit[ms]: ");
    Serial.println(MillisZeit);
    Serial.print("\n");
  }
  /*
    else if (StartWert > EndWert)
    {
      for (int i = StartWert; i >= EndWert; i--)
      {
        PWMOutput(Pin, i, 300);
      }
    }
  */
}

void PWMOutput(int Pin, int PWM_Wert, float PWM_Freq)   // PWM_Wert 0-255 - Freq >61Hz sonst Probleme wegen max. Millis() Länge.
{
  long Zykluslaenge = 1000000 / PWM_Freq;
  float ProzentAN = PWM_Wert / 255.0;
  int AN_Zeit = ProzentAN * Zykluslaenge;
  int AUS_Zeit = Zykluslaenge - AN_Zeit;
  Serial.print("PWM_Freq ");
  Serial.println(PWM_Freq);
  Serial.print("PWM_Wert ");
  Serial.println(PWM_Wert);
  Serial.print("Zykluslaenge ");
  Serial.println(Zykluslaenge);
  Serial.print("ProzentAN ");
  Serial.println(ProzentAN);
  Serial.print("ON Time ");
  Serial.println(AN_Zeit);
  Serial.print("OFF Time ");
  Serial.println(AUS_Zeit);
  Serial.print("\n");

  if (AN_Zeit > 0)
  {
    ShiftRegOut.set(Pin, HIGH);
    delayMicroseconds(AN_Zeit);
  }
  ShiftRegOut.set(Pin, LOW);
  delayMicroseconds(AUS_Zeit);
}

[me-no-dev]

reason is that your whole routine is fully blocking for the cpu and it takes more than the watch dog permits (thus triggering soft wdt reset). The reason why it does not crash when you add delay() is that delay() actually switches the context back to the system while you are delaying and feeding the watchdog this way.

[Gorkde]

Yes but why is it working with delay(1) and not with delayMicroseconds(1000) ???

There must be something up right?

Will change it lateron anyway to work without delay but just discovered the problem while testing.

[me-no-dev]

and I just explained it to you. delay(1) will let the system run for 1ms. delayMicroseconds(1000) will halt for 1ms and not give the system a chance to do it's thing.

[Gorkde]

Ok, I assumed delayMicroseconds(1000) would do the same. So it doesn't?

[me-no-dev]

no it does not. The ESP as opposed to AVR Arduinos (and others) has WiFi and full network stack running in the background that needs to process the network often. When you delayMicroseconds you actually prevent that from happening and the longer you the, more the chance to soft wdt becomes. delay() on the other hand, returns power to the system and checks on return if the time for returning to your code has come and if not, gives power to the system again.
sort of

void delayMicroseconds(uint32_t us){
  uint32_t start = micros();
  while(micros() - start < us){}
}

vod delay(uint32_t ms){
  uint32_t start = millis();
  while(millis() - start < ms){
    yield();//give the system a chance to execute
  }
}

[Gorkde]

Thanks! Didn't know that.

[Gorkde]

Hmmmm...

Changed the PWM Routine now so it has no delay and removed the delay above but it crashes at the same point as it did before I added delay(1).

It always crashes at "PWM_Wert 194" once don't add delay(1) in the counting loop.

  if (AN_Zeit > 0)
  {
    unsigned long StartzeitAN = micros();
    ShiftRegOut.set(Pin, HIGH);
    while (micros() - StartzeitAN < AN_Zeit);
  }
  unsigned long StartzeitAUS = micros();
  ShiftRegOut.set(Pin, LOW);
  while (micros() - StartzeitAUS < AUS_Zeit);
}

[me-no-dev]

but it MUST have delay! else your routine takes too long and you crash the system

[me-no-dev]

or at least optimistic_yield(10000); or just yield();

[pieman64]

@Gorkde I believe what @me-no-dev stated was that delay(1) MUST be used as your routine "takes too long to run" but that you can't substitute delayMicroseconds(1000) for delay(1) i.e. delay(1) is a very specific function.

[Gorkde]

Ok, thanks, will include yield then!

[Gorkde]

One last question:

How often do I need to add delay(1) or yield() ?
What time could my loop take before I risk the ESP resetting?

And... is delay(1) enough or does it need to be a larger time?