same timer for 2 activities

[VStana]

i'm looking to use only one timer for two independent activities:

• battery service (as in Nordic examples) and
• a routine to detect a certain button press pattern (measure the on time and off time). The button is used only after wake-on, if the expected pattern is recognized the button is disabled and battery service initialized. I've created a timer, using app_timer_create; I will be started from button press event, or from battery event, as required.

Q1 : is it a good idea, or is better to define 2 define 2 timers, with two timeout handlers ?

Q2: how can i use the p_context pointer, to detect in the timer's timeout_handler what event started the timer ? is there any example of how this (void *p_context) should be used ?

Update 5 april. How to use p_context

1. Allocate a variable, which is not deleted when changing scope. (Either a global or static variable)
2. Pass a pointer to this variable as p_context in app_timer_start, after casting it to void*
3. In the timer event handler, cast this pointer to the correct datatype, and use it.

This is for example done in bsp.c in SDK 11:

1:

static uint8_t     current_long_push_pin_no; 

2:

err_code = app_timer_start(m_button_timer_id, BSP_MS_TO_TICK(BSP_LONG_PUSH_TIMEOUT_MS), (void*)&current_long_push_pin_no);

3:

static void button_timer_handler(void * p_context)
{
    bsp_button_event_handler(*(uint8_t *)p_context, BSP_BUTTON_ACTION_LONG_PUSH);
}

[Anders Strand]

Hey.

Q1:

Create two app_timer instances with one timeout handler each. This will not use two physical timers, but will separate the two timers in software. This will probably make your code more logically structured.

Q2:

The p_context pointer can be used to pass any data to the timeout handler. If you follow my advice in Q1, you do not need this to determine which event started the timer. The app_timer tutorial should help you if you want to use it.

See also the app_timer docs if you havent.

-Anders

[VStana]

Hi Anders, so you suggest to create 2 timers, each one with his own Id and his handler app_timer_create(&m_timer1_id, APP_TIMER_MODE_REPEATED,timer1_timeout_handler) and app_timer_create(&m_timer2_id, APP_TIMER_MODE_REPEATED,timer2_timeout_handler) In this way, I should also increase APP_TIMER_MAX_TIMERS, even if they are not started on the same time, correct ?

for Q2: I already read the tutorial and the doc(s), but I was not able to find how to use p_context. I will follow your suggestion on Q1, but i'm still curious how that context pointer can be passed to the timeout handler.

[Anders Strand]

You are correct about Q1. See my updated answer for how to use p_context.