APP Timer and While loop in BLE

[Siva]

Hi,

I am using App Timer for measuring time and at the same time while loop to check if the timer reached particular time.

I have noticed during while loop App Timer event doesn't seems to work. Is this correct?

Regards Siva

[Einar Thorsrud]

In what interrupt priority do you check the timer value in a loop? If it is running in the same or higher priority than the application timer, your timeout event handler will never be called as it must wait for the other (same or higher priority) interrupt handler / event handler to finish first.

[Siva]

Can you advice on how to change interrupt priorities for timer,ble, gpio, protocols(I2C,SPI,Uart,etc).

I have attached my code. At line 1067 where our problem actually starts.

1. We use "rtc_config()" to read touch value, I have noticed that it doesn't read data when it enters into the loop for the first time I have to call this function again by button press in order to read the data. It is recursive(I have to call the event twice to read the touch data). Any Advice?

2. In lines 1078,1091 where I started using while loop to check time.

You are correct if I can set the priorities right this should work. In our application ble,timer needs to be highest priority followed by I2C and then while/main loops.

[Siva]

I found how to set IRQ priorities for Protocols now.

[Siva]

I have tried changing "APP_IRQ_PRIORITY_LOW" to "APP_IRQ_PRIORITY_HIGH" on RTC1 in nrf_drv_config.h file but it didn't work as it still got stuck in while loop.

[Einar Thorsrud]

Do you really need to do so much in an interrupt context? And do you really need those loops waiting for a long time? It tends to give you a complex application where it is difficult to handle what is waiting for what (as you are seeing). Moreover, the CPU will be running for much of the time, causing an unnecessarily high current consumption.

There are other issues with your code as well. In your Peace_Mask_Active(), where you have for example this loop:

		while(true)
		{
			if(Current_Time_Sec > (Measured_Treatment_Time+20))
			{
				break;
			}
		}		

you are waiting for Current_Time_Sec to change, which is updated in another event handler (in interrupt context). Even if you make sure that the Current_Time_Sec is updated in an event handler with higher priority (which is a must), it still won't help you unless you disable optimization, as the variable is not volatile and the compiler cannot easily know that it can change. Therefore, with normal optimization, the above loop would be optimized to something like this:

		while(true)
		{
		}	

...which will continue to do nothing forever. (As long as you are just incrementing and waiting for it to become larger than a limit, making the variable volatile should be sufficient in this case. In other cases you would have to do more in order to make the operation atomic, using for example the CRITICAL_REGION_ENTER() and CRITICAL_REGION_EXIT() macros supplied with the SDK.)

[Siva]

Hi Einar, Thanks for your advise. I am also thinking to use another "App timer" with low priority such that I will use it to call "Peace_Mask-Active()" event once every few seconds(It doesn't has to be very accurate).

I didn't find a correct syntax to change priorities for App timer can you advice on this please. Also want to know which RTCs has been used while using multiple app timer functions.