error: DWT implements no cycle counter. Cannot be used for cycle counting.

[moose]

Hello, I tried to implement the zephyr executing time functions API on my nrf52 hardware and I got the above error. According to my SoC documentation (nRF52833), this hardware does include a DWT counter. I am not sure if I need to do anything special to configure this hardware or if I need to use a relevant nrfx driver. My code was very similar to the example code in the zephyr documentation mentioned here https://docs.zephyrproject.org/latest/reference/timing_functions/index.html. Any inputs? Thx!

[moose]

Any update on this? I am still experiencing the same issue. Thx!

[Sigurd]

Hi,

There was a bug in earlier NCS versions that made this ASSERT to be ignored(warning about this was printed in the build log).

It's now asserting in NCS v1.6.x.

It looks to be bug in Zephyr, and I have reported it to the developer. 

In the code we have:
__ASSERT((DWT->CTRL & DWT_CTRL_NOCYCCNT_Msk) != 0,

It should be 
__ASSERT((DWT->CTRL & DWT_CTRL_NOCYCCNT_Msk) == 0,

From ARMv7-M Architecture Reference Manual:
NOCYCCNT, bit[25] Shows whether the implementation supports a cycle counter:
0 Cycle counter supported.
1 Cycle counter not supported

From ARMv8-M Architecture Reference Manual:
NOCYCCNT, bit [25]
No cycle count. Indicates whether the implementation does not include a cycle counter.
The possible values of this bit are:
0 Cycle counter implemented.
1 Cycle counter not implemented.

[davege]

Thanks for the follow up Sigurd.

Good to know it is just a minor bug in the code.

Could you keep us posted here on the resolution from the developers?

Thanks

D

[Sigurd]

Sure, I can post a link to the github PR here when it's created.

[davege]

Sigurd do you know if this fix will be included in the next Zephyr version?

Any update would be welcome.

Thanks

D