How to start with sleepy code in nRF connect Desktop SDK

RE: How to start with sleepy code in nRF connect Desktop SDK

Einar Thorsrud — Wed, 13 Mar 2024 14:16:38 GMT

As I mentionned before, the CPU will sleep by default as long as you don't do anything. But if any peripherals etc are enabled, they will continue to be. What do you use in your application? A typical problem is UART if you have logging enabled. So the first thing you should make sure is to disable logging, by adding configs like these:

CONFIG_CONSOLE=n
CONFIG_UART_CONSOLE=n
CONFIG_SERIAL=n
CONFIG_LOG=n

RE: How to start with sleepy code in nRF connect Desktop SDK

Pranathi CH — Wed, 13 Mar 2024 13:12:43 GMT

I am using the nRF52840 development kit for my evaluation.

I currently bought it to 150 uA by using thi function (previously it was 4.8mA).

pm_device_action_run(cons, PM_DEVICE_ACTION_SUSPEND);

in the main thread with K_sleep of 1000 micro seconds.

I want to reduce the current consumtion from 150 uA, for which I was going through the datasheet

I could see different sleep modes for the nRF52840 board, how do I enable them?

Could you please provide me some reference to this? or suggest me a example code releted to enabling these sleep modes?

RE: How to start with sleepy code in nRF connect Desktop SDK

Pranathi CH — Wed, 13 Mar 2024 05:40:23 GMT

Thank you for your comprehension and guidance. I will notify you once I have completed the mentioned procedure.

RE: How to start with sleepy code in nRF connect Desktop SDK

Einar Thorsrud — Tue, 12 Mar 2024 13:34:46 GMT

I understand. I am not interested in your logic, but if you measure a unexpected high current consumption and want input on what oculd cause it I need to know more about the application you run, the hardweare you are testing on and how you measure.

So, if you would like to proceed, I suggest the following:

Test with a simple application that has logging disabled and does nothing other than either return from main or have an empty main loop with a k_sleep with a long delay. This way, the CPU should sleep for a long time and no peripherals that can consume significant amount of power will be active.
Measure the current consumption of that to get the base of your device.
Is that much higher than expected? If so, we need to first look at your hardware and measurment setup.
Is it in the order of a few micro amps (which is expected)? If so, we need to look at your firmware to understand why you get an unexpected current consumption.

RE: How to start with sleepy code in nRF connect Desktop SDK

Pranathi CH — Tue, 12 Mar 2024 13:22:55 GMT

My actual code consists the logic, I just shared you the syntax of where I was using the sleep.

And I didn't check the current consumptions with the code as it is I provided in the above reply, I checked the currents with my logic in it. That's why I have mentioned "my code" and "my logic" so that you can understand that there is some logic I have written there which I couldn't share in the dev zone as it is irrelevant.

RE: How to start with sleepy code in nRF connect Desktop SDK

Einar Thorsrud — Tue, 12 Mar 2024 13:15:50 GMT

I see. Nothing obviously stands out here. If you comment out your logic and keep only the sleep, what current consumption do you measure then? If that is also high, you need to look somewhere else. Either in other parts of the application, or it oculd also be worth looking at your hardware and how you measure the current consumption.

RE: How to start with sleepy code in nRF connect Desktop SDK

Pranathi CH — Tue, 12 Mar 2024 13:05:23 GMT

I am using a thread that is defined as

K_THREAD_DEFINE(control, 1024, control_thread, NULL, NULL, NULL, -1, 0, 1000);

And at the end of the entry "control_thread" function I am using k_sleep(K_MSEC(50));

int main(void)
{
    #My code#
    
    return 0;
}

void control_thread(void)
{
    while(true)
    {
        #My logic#
        k_sleep(K_MSEC(50));
    }
}

K_THREAD_DEFINE(control, 1024, control_thread, NULL, NULL, NULL, -1, 0, 1000);

RE: How to start with sleepy code in nRF connect Desktop SDK

Einar Thorsrud — Tue, 12 Mar 2024 12:57:42 GMT

[quote user="Pranathi CH"]Can I use k_sleep(K_FOREVER) in my code (in main) to make my system go in constant sleep and then use an RTC as a wakeup source to wake the core of my system?[/quote]

No, that is not how it works. If you don't want the main thread (or any other thread for that matter) anymore, just let it return. The idle task always runs.

[quote user="Pranathi CH"]I am getting around 5mA of current consumption without any sleep exhibited and I am aiming to reduce the current consumption for a better battery life.[/quote]

Can you share what you are doing? If for instance you have an eternal loop with no sleep so that the CPU is on 100% that could give you numbers of that magnitude.

RE: How to start with sleepy code in nRF connect Desktop SDK

Pranathi CH — Tue, 12 Mar 2024 11:51:54 GMT

Hi,

Can I use k_sleep(K_FOREVER) in my code (in main) to make my system go in constant sleep and then use an RTC as a wakeup source to wake the core of my system?

I am getting around 5mA of current consumption without any sleep exhibited and I am aiming to reduce the current consumption for a better battery life.

RE: How to start with sleepy code in nRF connect Desktop SDK

Einar Thorsrud — Tue, 12 Mar 2024 11:39:59 GMT

Hi,

They key point regardign sleep is that you can forget about the sleep, as that is handled automatically. Whenever you do not do anything, the kernel automatically ensures that the device sleeps in sytem ON low power mode (waiting for events/interrupts).

Note that the timers you describe are not low power, and they are normally never used while in sleep. Instead, an RTC instance is used for keeping track of time, and that is handled for you by the Zephyr kernel, which proivde many APIs for that (see Kernel Timing).

For isntance, you can make threads thta sleep and wake up every x amount of time, or threads that sleep because of soemthing else, or you can use dalayed items in a workqueue in order to schedule work to be done at a specific time in the future.

We are finishing up a more advanced course on this that we plan to release shortly, which I recomend you take a look at (this is indended as a natural continuation of nRF Connect SDK Fundamentals course, which I suggest you look at when it is available (you should also look at the Fundamentals course if you have not).

RE: How to start with sleepy code in nRF connect Desktop SDK

Pranathi CH — Tue, 12 Mar 2024 10:23:21 GMT

As per my previous reply, my requirement is:

My nRF should be in sleep all the time and it should wakeup when I want to implement a funcitonlity and this wakeup should happen with the help of a timer (as in we have 4 timers or 5 timers in nRF52840).

But in the blinky example I am more like in control with the sleep functionlity rather than in control with my functions I want to execute. by default, I want my board to be in sleep mode and by utilizing the timers (TIMER0/TIMEER1/TIMER2/TIMER3..) I want to wake the board up and after it wakes up I want to implement my functions and put my board back to sleep mode.

Thanks,

Pranathi

RE: How to start with sleepy code in nRF connect Desktop SDK

Einar Thorsrud — Mon, 11 Mar 2024 13:35:42 GMT

Hi,

You can for instance refer to the Blinky sample. This toggles a ledd in a loop and sleeps in between. As nothing else is happening, the system automatically enters system ON low power mode during this time.

RE: How to start with sleepy code in nRF connect Desktop SDK

Pranathi CH — Mon, 11 Mar 2024 13:17:09 GMT

Hi,

Can you provide me a sample code for some clear refernece for my side?

I want to use a timer based sleep mechanism as such I want the board to wake up when I am trying to exhibit a functionlity and after executing it my board should go into sleep and wake up when the said functionlity to be executed. And FYI I am using nRF52840 DK.

Thanks,

Pranathi.

RE: How to start with sleepy code in nRF connect Desktop SDK

Einar Thorsrud — Mon, 11 Mar 2024 12:37:11 GMT

Hi,

Th enRF Connect SDK includes the Zephyr RTOS, where there is always a idle thread that enters sleep mode when idle. So you do not need to do anything special to enter sleep, other than don't do anything. Note that for instance having a main loop that runs continiously means using the CPU at all times, so if you do, you can for instance wait with k_sleep() to sleep for a specified ammount of time.

RE: How to start with sleepy code in nRF connect Desktop SDK

Pranathi CH — Mon, 11 Mar 2024 11:20:17 GMT

Can you refer me a timer based sleep code?