Hello, in all example code the comparison is of the form millis() - millisLast >= Interval I was wandering if the following code could break when executed while milli is at the vicinity of 2 power32 Thanks! #define sp Serial.print #define spln Serial.println #define sp_ sp(F(" ")) void setup()…

unsigned long endTime=millis()+5UL*1000UL; This will fail because you are using addition so millis() will not become greater than endTime when the addition goes over the rollover value. Calculations involving millis() are safe if you use unsigned long variables and subtraction for comparisons As …

In addition to what UKHeliBob said, you might as well just use a delay there...unless this was a hypothetical question.

@ UKHeliBob - Thanks. I do not fully unerstand but will use the recommended form @ ToddL1962 - Thanks. I simplified the code to ease the discussion while maintaining the form I wished I could use

[image] guy_c: I do not fully unerstand but will use the recommended form See my past posts if you like. [image] Flashing LEDs, and mills() rollover Project Guidance Since it is calculated with unsigned long, it works fine unless you have twice or more rollovers. I…

[image] guy_c: unsigned long endTime=millis()+5UL*1000UL; Maybe then put another way. Exactly 5ms before the the rollover of millis() (which, incidentally, occurs about 50 days after system start), endTime will have the value 0. So then,when this test is performed if (millis()>endTime), mil…

[image] guy_c: I do not fully unerstand This may help (or not !) To keep things simple let's work with byte sized unsigned values named currentTime, previousTime and period When a byte sized variable overflows its value goes from 255 to 0 period will have a constant value and the other 2 …

@ UKHeliBob Thank you. Now assume I use my approach where the target time (say some time to act) is the current time + period, 8 bits unsigned starting current=248 target=248+5=253 current=249 do nothing current=250 do nothing current=251 do nothing current=252 do nothing current=253 act; tar…

Try this byte count = 240; byte period = 5; byte target = count + period; void setup() { Serial.begin(115200); while (!Serial); } void loop() { Serial.print("count:"); Serial.print(count); Serial.print("\ttarget:"); Serial.println(target); count++; if (count >= target) { Ser…

Here is the same thing illustrated using unsigned ints uint16_t count = 65522; uint16_t period = 5; uint16_t target = count + period; void setup() { Serial.begin(115200); while (!Serial); } void loop() { count++; Serial.print("count:"); Serial.print(count); Serial.print("\ttarget:"); …

Millis() arithmetic

Projects General Guidance

chrisknightley July 27, 2021, 5:25am 5

See my past posts if you like.

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Millis() arithmetic

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