Sandra Witzen

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5 years, 8 months ago.

Why is wait() different when using mbed and mbed-os libraries?

When using mbed library the wait() function works properly; for example when using blinky the time on and off of the LED is correct. However, when using the mbed-os library the wait function waits 10x as long. This was observed using an LPC1768

2 Answers

Zoltan Hudak
5 years, 8 months ago.

Hello Sandra,

It could be due to old firmware. Try to update.

Similar issues:

https://os.mbed.com/questions/81086/Wait-function-is-too-long-in-offline-com/

https://os.mbed.com/questions/78806/LPC1768-MBED-OS-5-wait_ms/

Peter Nguyen
5 years, 8 months ago.

Hi Sandra,

The reason why mbed wait is faster than mbed-os is because mbed-os contain an RTOS while mbed is not. For >1ms waits, the thread can be preempted to save power in mbed-os. To fix it, you will need to put the time-sensitive code in a critical section.

critical section

core_util_critical_section_enter();
do_timing_thing();
wait(0.5);
core_util_critical_section_exit();

Please let me know if you have any questions!

- Peter, team Mbed

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