Fix Underflow When Timer Created Inside Timer Handler #7
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Owner
|
Thanks for contributing to arduino-timer. However, this change breaks time overflow/rollover handling. One way to accomplish what you want in your example is to create a separate timer instance for your sub events: #include <timer.h>
auto timer = timer_create_default();
auto sub_timer = timer_create_default();
bool longTask() {
Serial.println("Starting!");
delay(50); // simulate really computationally intensive work
Serial.println("Finally finished!");
sub_timer.in(1000, [](void*) {
Serial.println("An entire second after finishing");
return false;
}); // This task will never wait.
return true;
}
void setup() {
Serial.begin(9600);
timer.every(2000, longTask);
}
void loop() {
timer.tick();
sub_timer.tick();
}I will update the documentation to clarify that adding timer events within another event is not supported. |
Owner
|
Please try the code at mc/fix-task-within-handler. It should support adding a task within a timer handler. Thanks for helping improve the arduino-timer library. |
Owner
|
The fix for this issue is now in master version 1.0.1. Closing. |
Author
|
Wonderful! Thanks for the fixes, that works perfectly! |
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When a timer is made within a timer handler, it is possible to end up with an underflow with the duration-since-start calculation. Code demonstrating the bug is as follows:
This causes the 1000ms delay to happen instantly instead of waiting. The serial output on my Arduino Uno is:
After applying my fix, it is as follows:
This is the correct behavior.
There are two ways of solving this issue, first would be to use signed longs everywhere that duration is used, but I have concerns about overflow on long-running projects, the second is to just ensure the duration isn't negative with a check. This is more computationally expensive, but I believe it should be negligible. A task can't wait for a negative time, so this case will only happen when this bug is showing its face.