Timers for nRF51822 Beacon Kit

[Sarah]

Hi,

In my project, I need to periodically perform some jobs on the nRF51822 Beacon kit (sdk 7.1). For that, I think I need to use timers. However, I'm not sure how to do this. I found some sample code online but it wasn't very explanatory.

Could you please give me some pointers to where I should be looking at or some sample code with explanation?

Any help will be much appreciated! Thanks

[Susheel Nuguru]

You Initialize the APP timer, read about APP_TIMER_INIT in app_timer.h, APP_TIMER_MAX_TIMERS should atleast be equal to number of times you use app_timer_create in your whole application

APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_MAX_TIMERS, APP_TIMER_OP_QUEUE_SIZE, false);

Then you create a timer by

app_timer_create(&m_leds_timer_id, APP_TIMER_MODE_SINGLE_SHOT, timeout_handler);

or

app_timer_create(&m_leds_timer_id, APP_TIMER_MODE_REPEATED, timeout_handler);

Singleshot will make your timeout_handler run once and then disable the timer, repeated on the otherhand will call your timeout_handler repeatedly with interval of configured timeout.

Now you have initialized the app_timer and also created your timer. Now we configure the timer and start it by

app_timer_start(m_leds_timer_id, APP_TIMER_TICKS(MS, APP_TIMER_PRESCALER), NULL);

now your timeout_handler will be called after INTERVAL_IN_MS

[Sarah]

Thank you very much! I get the error "invalid declaration of function BSP_MS_TO_TICK is invalid in C99 ". How can I fix this?

[Susheel Nuguru]

sorry my bad, copy paste mistake, changed my answer, instead of BSP_MS_TO_TICK macro use macro APP_TIMER_TICKS defined in app_timer.h. Its purpose is to convert the milliseconds delay you require to timer tick.

[Sarah]

Thanks very much Aryan, it works now. I have another question. I would like to use the single shot timer and when the timeout handler is called, I would like to set up the same timer again with different interval this time. Do I have to use both of the app_timer_create and app_timer_start functions, or would just using app_timer_start suffice? (In other words, I'm not sure whether the timer needs to be recreated or not). Thank you!

[Susheel Nuguru]

This is very good question, to make it more visible to others, please create another question for this with a good title. I will follow up. Thanks for your patience.