timer accuracy

[alex kim]

Hi,

I am using 

• nRF52840
• SDK 15.3.0
• Keil IDE
• The soft device is S140 
• JLinkRTTViewer for debug

I am using app_timer to control the LED On time.

the app_timer works correctly without SD event.

However, when an SD event (e.g disconnect) occurs, the LED is turned on for a shorter time than the app_timer value.

Question 1

     Why does this happen?

     Is it because app_timer priority is lower than SD event?

Question 2

   Which timer should be used to be less affected by SD events?

Please advise.

[CheMax]

Hi,

alex kim said:

Why does this happen?

Is it because app_timer priority is lower than SD event?

Yes. App timer it's software timers based on one hardware timer.

alex kim said:

Question 2

Which timer should be used to be less affected by SD events?

Another hardware timer with PPI for GPIOTE control. Yes, it is resource-intensive, but in this case you will not have problems managing the LED flashing. It will happen automatically without the participation of code and the kernel.

Or for example, you can use the PWM module. At least 2 flashing modes can be arranged on it. But you need to spend a little time studying the documentation.

Good luck

[Jørgen Holmefjord]

Check out the GPIOTE Example in the SDK.

[CheMax]

a small addition, in this example, Timer0 is used, which takes the SD to fit your needs. therefore, to work simultaneously with SD s140, you need to use another free timer.