ESP8266 Community Forum

Posted: **Wed Sep 14, 2016 5:23 pm**

The following code keeps an LED on while it is running. The code below works perfectly.

  for(q=0;q<10;q++) {
    for(y=0;y<20;y++) {
      if(y<20) {
        /* One cycle of HIGH */
        for(x=0;x<8;x++) {
          for(i=0;i<8;i++) {
            digitalWrite(serialIn, HIGH);
            digitalWrite(srck, HIGH);
            digitalWrite(srck, LOW);
          }
          digitalWrite(latch, HIGH);
          digitalWrite(latch, LOW);
        }
      } else {
        /* One cycle of LOW */
        for(x=0;x<8;x++) {
          for(i=0;i<8;i++) {
            digitalWrite(serialIn, LOW);
            digitalWrite(srck, HIGH);
            digitalWrite(srck, LOW);
          }
          digitalWrite(latch, HIGH);
          digitalWrite(latch, LOW);
        }
      }
    }
  }

However when I change "for(q=0;q<10;q++)" to "for(q=0;q<10000;q++)" it runs fine for a few seconds and the LED on the ESP8266 flashes and the LED the code is controlling goes out for a second or two, so I guess the ESP8266 rebooted. The entire code is below.

Code: Select all

int srck = 15;
int latch = 13;
int reset = 12;
int serialIn = 14;

int x = 0;
int i = 0;
int y = 0;
int z = 0;
int q = 0;

void setup() {
  pinMode(srck, OUTPUT);
  pinMode(latch, OUTPUT);
  pinMode(reset, OUTPUT);
  pinMode(serialIn, OUTPUT);
  
  
  digitalWrite(srck, LOW);
  digitalWrite(latch, LOW);
  digitalWrite(reset, LOW);
  digitalWrite(serialIn, LOW);  

  digitalWrite(reset, HIGH);delay(1);
  digitalWrite(reset, LOW);delay(1);
}

void loop() {
  for(q=0;q<10000;q++) {
    for(y=0;y<20;y++) {
      if(y<20) {
        /* One cycle of HIGH */
        for(x=0;x<8;x++) {
          for(i=0;i<8;i++) {
            digitalWrite(serialIn, HIGH);
            digitalWrite(srck, HIGH);
            digitalWrite(srck, LOW);
          }
          digitalWrite(latch, HIGH);
          digitalWrite(latch, LOW);
        }
      } else {
        /* One cycle of LOW */
        for(x=0;x<8;x++) {
          for(i=0;i<8;i++) {
            digitalWrite(serialIn, LOW);
            digitalWrite(srck, HIGH);
            digitalWrite(srck, LOW);
          }
          digitalWrite(latch, HIGH);
          digitalWrite(latch, LOW);
        }
      }
    }
  }
}

Does anyone have any idea why it would be acting like this?

Posted: **Thu Sep 15, 2016 8:09 am**

Perhaps your loop is too long, and that triggers the watchdog.

Posted: **Thu Sep 15, 2016 9:00 am**

You're right, it was the long loop, I had it in my head it was some kind of memory leak. Adding delay(0) to the outer loop stopped the resets. I checked the performance hit of adding the delay; it took 5970 nanoseconds, for context a digitalWrite takes 450 nanoseconds.

Cheers!

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