some question of nrf51822 timer

[hjjeon]

I am developing using a nrf51822.I need delay timer that can be substitued for nrf_delay_ms(). in other words,need a task delay that can be taken some event from another side during delay time. Is nrf_timer_delay_ms() possible ? If so,please tell me how to use and attention point regarding sw side and hw side. BR

[Stefan Birnir Sverrisson]

Hi hjjeon

There are two kinds of hardware timers, TIMER and RTC. TIMERs can generate events with up to 16MHz frequency while the RTC timer can generate events with up to 32 kHz frequency. Benefit of using RTC is that it is power efficient.

I attach a TIMER example that uses the TIMER interrupt. While waiting for the TIMER interrupt, you can use the CPU to perform other tasks.

If you are interrested in using the RTC timer, take a look at the rtc_example in the nRF51822 SDK which uses RTC interrupt.

timer_example_timer_mode.zip

[hjjeon]

thank you for your consideration

[hjjeon]

I can use the timer .but All i need is time delay function. I can't make this using a timer caused by my stupid. Could you help me?

[Stefan Birnir Sverrisson]

Hi hjjeon

If you want to sleep during your delay instead of executing code, in order to save power, you can do the following:

1. Set up your TIMER interrupt with the desired delay and enable the interrupt.
2. When you want a delay, start the timer and go to sleep with the __WFI command (see nRF51 Series Reference Manual (RM) v2.1, section 11.1.3.
3. When the timer expires, it will generate an interrupt, the chip will wake up and execute your defined interrupt handler.
4. The TIMER interrupt handler stops the TIMER and resets it, making the TIMER counter to be zero.
5. When the interrupt handler finishes execution, code execution will continue in the main thread, starting with the command after your __WFI command.
6. Whenever you want a delay again in your code execution, simply start the timer and issue __WFI command.

[hjjeon]

I made like below.Please review my code which one is the best for taking another timer event during delay.or if it's wrong, inform me.

void nrf_delay_ms(uint32_t volatile number_of_ms) { while(number_of_ms != 0) { __WFE(); __SEV(); __WFE(); number_of_ms--; nrf_delay_us(999); } }

void nrf_delay_ms(uint32_t volatile number_of_ms) { while(number_of_ms != 0) { __WFI(); number_of_ms--; nrf_delay_us(999); } }