[SOLVED] OS_GetTime32() Return Parameter range ?

PTepe · May 24th 2018, 10:30am

Hi, I have the following question:
According to the manual the return value is a 32 int. This int ist a signed int. Does this mean that after (2^31) the value gets negative or 0? What happens after the overflow?

SEGGER - Michael · May 24th 2018, 3:48pm

Hello PTepe,

Yes, OS_GetTime32()'s return type is a signed 32 bit integer. However, the signed/unsigned is just how the binary value is interpreted, and doesn't change it's binary representation. Therefore, if the overflow from ((2^31) - 1) to (2^31) occurs, the binary value continues counting upwards from (2^31) up to ((2^32) - 1).

Best regards,
Michael

SEGGER - Til · May 24th 2018, 4:10pm

Hello PTepe,

just two additional notes:

1. Overflow is no problem for all our timeout functions like OS_TASK_Delay(). It simply works!
You can also use it for yourself as long as you are working with signed subtractions between two OS_GetTime32() values.

2. If you just need the absolute system time after reset you can also use OS_TIME_Getus64() which returns the current system time in microseconds as a 64 bit value.
With this 64 bit value OS_TIME_Getus64() can return up to 18446744073709 seconds or ~584942 years before an overflow occurs (should be sufficient for most applications

).

Best regards,
Til

PTepe · May 28th 2018, 9:35am

Hi Til,
Hi Michael,

Thank you for the reply and examples.
In my EmbOS version I don't have OS_TIME_Getus64() but I do the substraction and now I'm also sure what the return range of OS_GetTime32() is.

SEGGER - Martin · May 28th 2018, 3:10pm

Hi PTepe,

Thanks for your feedback, we'll consider this case solved then.

PTepe wrote:

In my EmbOS version I don't have OS_TIME_Getus64() but I do the substraction and now I'm also sure what the return range of OS_GetTime32() is.

This function was called OS_GetTime_us64() with previous versions of embOS. Since V5.00, it's called OS_TIME_Getus64().

Best regards,

Martin

Share