Hi,
I'm trying to implement a slow timer which is supposed to be triggered about every 30 minutes or even less frequent, but I'm kind of clueless how to solve this issue.
I tried implementing the app_timer first, as described in this post: https://devzone.nordicsemi.com/nordic/short-range-guides/b/software-development-kit/posts/application-timer-tutorial
but unfortunately I did not find a function or parameter to change the frequency or prescaler of this timer, so for this use-case the app_timer was not the best choice.
(Unless I would catch every interrupt and count them up, which I like to avoid)
As this is a low power application, I want to create as few interrupts as possible and after I read that you can use the RTC to create timers up to 8 hours, I tried to implement that.
Now, I'm basically left with 2 questions:
-
Is there something I need to pay attention to? Like for example messing with the clock configuration. (And I already figured you cannot use instance 0 of the RTC, with this example)
-
And how do I set up the compare interrupt, in a way, that it triggers repeatably?
Here are the steps I've taken so far:
My code is based on the LPN Example from the Mesh SDK.
I attempted to implement the RTC as demonstrated in the SDK\examples\peripheral\rtc example.
static void rtc_handler(nrf_drv_rtc_int_type_t int_type)
{
if (int_type == NRF_DRV_RTC_INT_COMPARE0)
{
__LOG(LOG_SRC_APP, LOG_LEVEL_INFO, "COMPARE0 match\n");
}
else if (int_type == NRF_DRV_RTC_INT_TICK)
{
__LOG(LOG_SRC_APP, LOG_LEVEL_INFO, "TICK event\n");
}
}
static void lfclk_config(void)
{
ret_code_t err_code = nrf_drv_clock_init();
APP_ERROR_CHECK(err_code);
nrf_drv_clock_lfclk_request(NULL);
}
/** @brief Function initialization and configuration of RTC driver instance.
*/
static void rtc_config(void)
{
uint32_t err_code;
//Initialize RTC instance
nrf_drv_rtc_config_t config = NRF_DRV_RTC_DEFAULT_CONFIG;
config.prescaler = 4095;
err_code = nrf_drv_rtc_init(&rtc, &config, rtc_handler);
APP_ERROR_CHECK(err_code);
//Enable tick event & interrupt
nrf_drv_rtc_tick_enable(&rtc,true);
//Set compare channel to trigger interrupt after COMPARE_COUNTERTIME seconds
err_code = nrf_drv_rtc_cc_set(&rtc,0,COMPARE_COUNTERTIME * 8,true);
APP_ERROR_CHECK(err_code);
//Power on RTC instance
nrf_drv_rtc_enable(&rtc);
}
int main(void)
{
initialize();
start();
// lfclk_config(); <- causing Error 133
rtc_config();
for (;;)
{
(void)sd_app_evt_wait();
}
}
On the first run I got Mesh error 133, wich I think is caused because the function initialize() is probably using the clock somewhere else.
Therefore I used the rtc_config() without calling lfclk_config() first, which seems to work.
It is working in the sense, that ticks is called permanently, but compare is only called once after a certain number of ticks (which makes sense, I just expected it to trigger again after a wrap around of the RTC).
This behaves the same, even when I'm trying to set up a new compare in the rtc_handler.
Since I'm not sure if that is even the proper way of doing things, it would be great to get some advice: How I can start/stop and modify the RTC and if it's fine ignoring the set up of the clock (in this example), or how to do that correctly.
Sincerely,
Heiner
