nrf52 timer example, over 5 minutes event handler.

Question

When I test the timer example with nrf52832 DK, it so nice to 4 minutes. 
 uint32_t time_ms = 240000;
 
 But when I set the time interval over 5 minutes, then the event handler run more rapidly. 
 So, what should I do for long time period?

Jørgen Holmefjord · Accepted Answer

Hi JW, 
 By default, the timer runs at 16 MHz and the maximum bit width of the timer is 32-bit. This corresponds to a maximum timer value of: 
 (2^32)-1 = 4294967295
 
 The reason why you see event handler more rapidly with 5 minutes, is that nrf_drv_timer_ms_to_ticks use the configured frequency and the time_ms parameter to generate the number of ticks, and return this in a 32 bit variable: 
 5*60*16000000 = 4800000000
 
 This overflows the 32 bit variable, giving you a tick count of 505032705 = ~31.5 seconds. 
 You need to change the frequency of the timer to make it run run slower. This is done by changing the timer configuration: 
 timer_cfg.frequency = NRF_TIMER_FREQ_8MHz;
 
 You can set it to any of the frequencies documented here . 
 Best regards, 
 Jørgen