Values of RTIMER_ARCH_SECOND for frequencies rather than 32MHz, such as; 24MHz, 16MHz and 12MHz

[Wassim Ben Chikha]

Posted on November 13, 2017 at 15:04

Hello all,

Using

STM32L1XX_NUCLEO

with

F_CPU

equal to

32

MHz

,

the

RTIMER_ARCH_SECOND

is

defined as

32768 in the file platform-conf.h.

Please,

what are

the value

s

of

RTIMER_ARCH_SECOND

for frequenc

ies

rather than 32MHz,

such as;

24MHz, 16MHz and 12MHz?

M

any thanks for your time and look forward for your response.

B

est regards,

Wassim

[Uwe Bonnes]

Posted on November 13, 2017 at 15:32

32768

seems related to the RTC quarz.

[Tesla DeLorean]

Posted on November 13, 2017 at 15:58

It's really a Contiki OS thing, are you sure they are even directly related? Or just a fractional representation of another clock?

[Wassim Ben Chikha]

Posted on November 13, 2017 at 16:18

As seen in the following link, the RTIMER_ARCH_SECOND is given by F_CPU/RTIMER_ARCH_PRESCALER, where RTIMER_ARCH_PRESCALER is eqaul to 1024.

http://contiki.sourceforge.net/docs/2.6/a00792_source.html

 

However, in the file /Middlewares/ST/Contiki_STM32_Library/Incplatform-conf.h, RTIMER_ARCH_SECOND is defined as: #define RTIMER_ARCH_SECOND 32768 for STM32L1XX_NUCLEO using F_CPU=32MHz and defined as: #define RTIMER_ARCH_SECOND 96000 for STM32F4XX_NUCLEO using F_CPU=84MHz. Hence, I am not sure if they are  directly related or not.