nrf_drv_timer interrupt handler get called instantly

RE: nrf_drv_timer interrupt handler get called instantly

Susheel Nuguru — Mon, 01 Feb 2016 21:20:12 GMT

Questchin,

I missed to see your comment, i would strongly recommend you not to directly write to timer registers when using nrf drivers. Nrf drivers had internal state machine, your code will not necessarily be compatible with future SDKs where they might store the value of prescaler inside the driver and then it would create a conflict.

RE: nrf_drv_timer interrupt handler get called instantly

Questchin — Mon, 18 May 2015 14:58:18 GMT

Thank you, Aryan! That is the problem. I simply use NRF_Timerx->PRESCALER = 4 to do this after the nrf_drv_timer_init() function. I know this is not the standard way of initialization while the SD is at present, but it works fine now. Thank you very much!

RE: nrf_drv_timer interrupt handler get called instantly

Susheel Nuguru — Mon, 18 May 2015 11:32:53 GMT

The problem is with your PRESCALER and time_ms. With PRESCALER = 0 in the timer you generate 0X3E80 (16000) ticks per millisecond. So for your 50ms number of ticks required is C3500. This does not fit in 16-bit TIMER1. Change the prescaler so that your time_ticks will be able to fit in 16-bit TIMER1 CC register.

changed the prescaler to 4 instead of 0 using

nrf_timer_frequency_set(STREAM_PAC.p_reg, NRF_TIMER_FREQ_1MHz);

after initializing the timer and it will work with the precision you need, which I verified by copying your timer code into ble_app_beacon_s110 example.

RE: nrf_drv_timer interrupt handler get called instantly

Questchin — Fri, 15 May 2015 14:23:19 GMT

Thank you for the input. Although I end up with using the app_timer, I found it not so accurate that I prefer to switch back to the this nrf_drv_timer. Would you please indicate some way of testing which reason it might be? I used have some issue regarding the bootloader since header files are always linked to the library file instead of the one I modified. I was wondering if that would be the issue.

RE: nrf_drv_timer interrupt handler get called instantly

Susheel Nuguru — Fri, 15 May 2015 10:07:33 GMT

If you changed the time interval and it really did not effect your timing then only three things can explain this.

1) someone else is using this timer overwriting your settings OR
2) the SHORT for compare and clear is not working somehow.
3) The PRESCALER for timer is small and your required time does not fit in Timer CC register