APP_TIMER_DEF for several timers with same timer id. like C++ class member

Question

hello 
 yes I have problems with my app_timers in SDK14.2 (migration from 12), 
 I well noticed that the prototypes of the functions create and start changed from sdk12.

// create timer

static app_timer_t timer_data = { { 0 } } ; 
 m_timer_id = & timer_data ; 
 err_code = app_timer_create ( & m_timer_id , APP_TIMER_MODE_REPEATED , cbk_measure ) ; 
 APP_ERROR_CHECK ( err_code ) ;

-> this works well

ret_code_t err_code ; 
 
 err_code = app_timer_start ( m_timer_id , APP_TIMER_TICKS ( m_probing_interval_ms ) , ( void * ) this ) ; 
 
 NRF_LOG_DEBUG ( " FIXME: app_timer_start returns %d " , err_code ) ; 
 // APP_ERROR_CHECK(err_code);

-> but the start returns error code 8 (invalid param if i remember correctly) and I dont understand why. I tried APP_TIMER_DEF, but my timer_ids are C++ class members. I cannot simply use the APP_TIMER_DEF macro because I dont know if it ok if already declared. but it was already the case ion SDK12 and worked AFAIK

thx, 
 yacine

yacine · Accepted Answer

self fixed: 
 in APP_TIMER_DEF macro, "static" allows to exist beyond the functin where it is called, after app_timer_create. hence you can call it later e.g. for the start function, but it also induces that every timer id with the same timer data... this is not good for instantiation/C++ or collections that uses the same timer_id variable name. 
 workaround = use malloc instead, which allocate a different memory area (good for several instantiation) and is opersistent (just like static) but you will need to free the memory when no more used. 
 
 // create timer
	m_timer_id = (app_timer_t *) malloc(sizeof(app_timer_t));
	memset(m_timer_id, 0, sizeof(app_timer_t));

Philip Odom · Answer

The APP_TIMER_DEF macro instantiates an app_timer_id_t with the name you provide and another variable of type app_timer_t with the name appended with _data. app_timer_id_t is just a pointer to the app_timer_t (app_timer_t *). For example: APP_TIMER_DEF(my_timer); expands to static app_timer_t my_timer_data = { {0} }; static const app_timer_id_t my_timer = &my_timer_data; So far so good, unless you want an app_timer to be a member of a struct or class, which is the problem I also ran into quickly. In that case, just do the same thing as the macro would, manually, and in your initialization code or constructor, set the app_timer_id_t member to the address of the timer. In C++: #include using std::uint32_t; class my_timer_class { public: my_timer_class() : timer(&timer_data) , timer_data() { app_timer_create(&timer, APP_TIMER_MODE_REPEATED, timer_handler_s); } virtual ~my_timer_class() { } void start_timer(const uint32_t ms) { app_timer_start(timer, APP_TIMER_TICKS(ms), this); } private: app_timer_id_t timer; app_timer_t timer_data; static void timer_handler_s(void *p_context) { ((my_timer_class*)p_context)->timer_handler(); } void timer_handler() { //timer expired, do something! } }; my_timer_class timer_object; int main() { //start object's timer qith 1000 ms period timer_object.start_timer(1000); } In C, you either have to do the initialization at the time of instantiation or not make the app_timer_id_t const: #include #include typedef struct struct_with_timer_s { const app_timer_id_t timer; app_timer_t timer_data; } struct_with_timer_t; //initialize timer_id (const) when declaring struct struct_with_timer_t struct_with_timer = {.timer = &struct_with_timer.timer_data}; void struct_with_timer_handler(struct_with_timer_t *const this) { //timer expired, do something! printf("tick "); } void struct_with_timer_static_handler(void * p_context) { struct_with_timer_handler((struct_with_timer_t *)p_context); } void struct_with_timer_init(struct_with_timer_t *const this) { uint32_t error_code = app_timer_create(&this->timer, APP_TIMER_MODE_REPEATED, struct_with_timer_static_handler); APP_ERROR_CHECK(error_code); } void struct_with_timer_start(struct_with_timer_t *const this, const uint32_t ms) { app_timer_start(this->timer, APP_TIMER_TICKS(ms), this); } int main(void) { //initialize struct struct_with_timer_init(&struct_with_timer); //start its timer with 1000 ms period struct_with_timer_start(&struct_with_timer, 1000); return 0; }

APP_TIMER_DEF for several timers with same timer id. like C++ class member

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