A safe "blocking" delay for use with watchdog timers

README.md

Safe Delay for μControllers

Most microcontroller platforms implement a watchdog timer that resets the controller if it detects a freeze. It does that by checking to see if the code has yielded. On some, a delay() that exceeds the watchdog timer's limits will initiate a reset.

This "safe" delay yields to the stack every tick to create a "blocking" delay in user code; however, internal functions like the watchdog timer are not blocked. It optionally prints a dot every second.

SafeDelay.cpp

//////////////////////////////////////////////////////////////////////////
//
// _delay:  A safe delay() replacement.  Delay by defined 32-bit number
//          of milliseconds (1 to 4,294,967,295 millis) or up to
//          4,294,967 seconds.  Yields to the stack every millisecond
//          in order to create a "blocking" delay in terms of user code
//          however internal functions like the watchdog timer are not
//          blocked.  Optionally print a dot every second.
//
// Args:
//      delayMillis:    Unsigned Long in millis()
//      printDot:       (optional) Print dot every second
//
//////////////////////////////////////////////////////////////////////////

#include <Ticker.h>
#include <Arduino.h>

void _delay(unsigned long delayMillis, bool printDot = false)
void _dot();

void setup() {
    Serial.begin(74880);
    Serial.println("\n");

    Serial.print("Start = ");
    Serial.println(millis());
    
    // Delay for 5 seconds, print dots each second
    _delay(5000, true);
  
    Serial.print("Finish = ");
    Serial.println(millis());
    Serial.println("Done.");
}

void loop() {}

void _delay(unsigned long delayMillis, bool printDot)
{
    // Safe blocking delay() replacement

    Ticker _dottimer;
    if (printDot)
    {
        _dottimer.attach(1.0, _dot);
    }

    unsigned long ulNow = millis();
    unsigned long ulThen = ulNow + delayMillis;
    while (ulThen > millis())
    {
        yield();
    }

    if (printDot)
    {
        Serial.println();
        _dottimer.detach();
    }
}

void _dot()
{
    Serial.print(".");
}