nrf9160dk: using HFCLK with Zephyr SDK

RE: nrf9160dk: using HFCLK with Zephyr SDK

parthitce — Thu, 12 Nov 2020 19:05:57 GMT

Thank you very much JONATHAN LL. Opened a issue in Zephyr mainline: https://github.com/zephyrproject-rtos/zephyr/issues/29977

RE: nrf9160dk: using HFCLK with Zephyr SDK

JONATHAN LL — Thu, 12 Nov 2020 14:50:31 GMT

Hi,

The SYS_CLOCK in Zephyr uses RTC and not a timer, so using these configs
CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=64000000
CONFIG_SYS_CLOCK_TICKS_PER_SEC=64000000

Will not work. I did some testing and even the hello_world example does not behave properly even though it looks like it worked at first glance. The same goes for Blinky and other basic examples. Something strange is going on when setting those values and it is not stable.

Using TIMER (max 16MHz) but I don't believe there is a implementation for this yet, or Systick (maybe 64MHz). This is not low power options so as far as i know it has not been considered by nordic as the RTC preforms well in this regard. Maybe looking at a different way to solve the problem could be better. I would recommend to take the question to Zephyr community an ask for help there.

Regards,
Jonathan

RE: nrf9160dk: using HFCLK with Zephyr SDK

parthitce — Tue, 10 Nov 2020 14:40:54 GMT

Good day JONATHAN LL, No I am not trying to get nano second resolution. As in the above example, if I set 10 timers expiring at the same time (eg. 20 seconds), I don't see all of them not expiring at 20 seconds.

I have even tried with `k_timer_remaining_get` to filter within the margin of 100 mill seconds but no luck still. This means that I am not getting even millisecond resolution.

> CONFIG_SYS_CLOCK_TICKS_PER_SEC is not able to go to 64MHz, maybe try 32768

This means nrf9160 timer can't run at 64Mhz or in other words it can run only at 32868Hz?

RE: nrf9160dk: using HFCLK with Zephyr SDK

JONATHAN LL — Mon, 09 Nov 2020 15:02:53 GMT

Hi,

CONFIG_SYS_CLOCK_TICKS_PER_SEC is not able to go to 64MHz, maybe try 32768
https://docs.zephyrproject.org/latest/reference/kconfig/CONFIG_SYS_CLOCK_TICKS_PER_SEC.html

Do you need Nano second accuracy?

Regards,
Jonathan

RE: nrf9160dk: using HFCLK with Zephyr SDK

parthitce — Thu, 05 Nov 2020 15:56:30 GMT

I am using NRF Zephyr SDK and toolchain. I did clone and compile based on : https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/gs_installing.html

Use case:

I have an application logic which needs multiple timers for managing various interface reading over modbus TCP. For example, I have 5 timers out of which 3 of them expires periodically every 10 seconds and remaining 2 at 20 seconds interval (implemented using https://docs.zephyrproject.org/latest/reference/kernel/timing/timers.html). I have a general timer (other than the 5) which runs at the lowest timer expiration value of all 5 and scans on all the 5 timers whether it's expired or not using k_timer_status_get. So I expect to see all 5 of them expires every 20 seconds.

As timer callback is in ISR context and I have a work thread which offloads all the primary interface reading. So every time the timer expires, the work is submitted and scheduled to offload. In the specific example above, during the 20 second interval, I wanted to process all 5 of them. But what I observed is, not all of them aren't expiring at the exact same time (k_timer_status_get).

So the idea is to process all the expired timers in work thread and read the interfaces.

I did try to compile and flash the hello_world example and it works with 64MHz clock. But not any other sample, like multi thread or mqtt.

static void reader_work(struct k_work *w)
{
        SYS_SLIST_FOR_EACH_CONTAINER(&gt->aq, aq, node) {
                if (k_timer_status_get(&aq->param.sec) > 0) {
                    /* application logic here */
                    
                    /* restart the timer */
                    k_timer_start(&aq->param.timer, K_SECONDS(aq->param.sec), K_NO_WAIT);
                }
        }
}

K_WORK_DEFINE(reader, reader_work);
static void periodic_reader(struct k_timer *t)
{
        k_work_submit(&reader);
}

void main(void) {
        SYS_SLIST_FOR_EACH_CONTAINER(&x->aq, aq, node) {
                if (period > aq->param.sec)
                        period = aq->param.sec;

                k_timer_init(&aq->param.timer, NULL, NULL);
                k_timer_start(&aq->param.timer, K_SECONDS(aq->param.sec), K_NO_WAIT);
        }

        k_timer_init(&reader, periodic_reader, NULL);
        k_timer_start(&reader, K_SECONDS(period), K_SECONDS(period));
}

I am expecting all the 5 timers to expire inside the worker thread. In reality there could be 100 timers in my use case.

My observation with the above logic is that the resolution of the timer is based on RTC at 32KHz. I would like to check the same logic with 64MHz clock (HFCLK). But enabling it leaving the target not booting.

RE: nrf9160dk: using HFCLK with Zephyr SDK

JONATHAN LL — Thu, 05 Nov 2020 15:23:29 GMT

Hi parthitce,

I am going to focus on this first:

[quote user=""]I am able to compile and run hello_world samples, but not other samples or custom application.[/quote]

Did you use the nrf connect for desktop Toolchain Manager app to install NCS v1.4.0 or are you using git and west pulling from master?
Is this statement related to Kconfig edits?

To clarify:
Are you not able to build and run any other applications then hello_world when you edit the kconfig file?

If you describe your end goal and use case then it might be easier to propose solutions

Regards,
Jonathan