How to configure FREERTOS Tasks for the following description

[Rajat]

Hi Everyone

My requirements are as follows

1. I am running 4 tasks using free rtos in which one measures the ADC , 2nd sends the adc data over BLE and 3rd check if the button is pressed or not and 4th sends the ADC data to LORA.

2. All my 4 tasks are running perfectly so far.

But i would like to have this feature in my code.

Whenever i press the button , the controller should come out of sleep mode and run the other 2 tasks of measuring adc and sending data over BLE.

As long as button is in low state(NOT PRESSED) ,the controller should remain in sleep mode and should not do anything.

My questions are

1. How to put the nrf52840 to Sleep mode ?

2. How to achieve the above described theory using FREERTOS Tasks.

3. Can i use mutexes and sempahores for the above theory?

4. What are the available Sleep modes on nrf52840.?

5. What are the functions to call to put nrf52840 to sleep modes?

[schef]

Hi,

about the sleep mode i think that the FREERTOS when no tasks are running is in idle task mode and that the idle taks is already in the deepest sleep mode (maybe nordic guys can confirm that).

I think that you could solve this issue using binary semaphores. You can check this video https://www.youtube.com/watch?v=grXuVMttVuU on how to use them. It could look like that:

xSemaphoreHandle button_signal = 0;
xSemaphoreHandle adc_signal = 0;

void button_interrupt_handler(){
    xSemaphoreGiveFromISR(button_signal);
}

void adc_task(void *p){
    while (1){
        if(xSemaphoreTake(button_signal, portMAX_DELAY)) {
	        //do the staff
    	    xSemaphoreGive(adc_signal);
	    }
    }
}

void ble_task(void *p){
    while (1){
        if(xSemaphoreTake(adc_signal, portMAX_DELAY)) {
	        //do the staff
	    }
    }
}

[Rajat]

I have watched that video previously.

We can also use binary semaphore for task to task instead of interrupt to task.

Am  i right?

[schef]

Yes, but when you use it in a task you use xSemaphoreGive instead of xSemaphoreGiveFromISR.

[Rajat]

I am a beginner with freertos, so correct me if i am wrong!!!

Inside the button task i will check for the state of button and if a button is pressed , i will simply call the xsempahoregive function .

Will that be enough or do i need to do something else for this!?

[schef]

Are you polling (reading the pin state every 100 ms) the button pin from a task or are you using GPIO interrupt? If you are polling you can use xSemaphoreGive but if you are using interrupt you have to use xSemaphoreGiveFromISR.

[Rajat]

I got your point 

Thanks!