Nrf52-timer-config

2021-04-25

Looking at some example code in nRF5SDK153059ac345/nRF5_SDK_15.3.0_59ac345/components/app_simple_timer.c, there are routines to init, start, stop (pause) and to uninitialize. Given a task to assure that a Nordic chip goes into lower or lowest possible power mode, we'll first examine the 'stop' and 'uninit' routines in this Nordic demo code.

The routine uint32_t app_simple_timer_stop(void) is a wrapper to nrf_drv_timer_pause(nrfx_timer_t const * const p_instance). Going through reverse engineering steps this routine is first defined via a macro:

  ./integration/nrfx/legacy/nrf_drv_timer.h:82:#define nrf_drv_timer_pause          nrfx_timer_pause

The definition of nrfx_timer_pause() is in the following .c file,

  ./modules/nrfx/drivers/include/nrfx_timer.h:186:void nrfx_timer_pause(nrfx_timer_t const * const p_instance);
  ./modules/nrfx/drivers/src/nrfx_timer.c:170:void nrfx_timer_pause(nrfx_timer_t const * const p_instance)

First Nordic demo code directories in which we're reviewing files:

nRF5SDK153059ac345/nRF5_SDK_15.3.0_59ac345/components/libraries/simple_timer
nRF5SDK153059ac345/nRF5_SDK_15.3.0_59ac345/modules
nRF5SDK153059ac345/nRF5_SDK_15.3.0_59ac345/modules/nrfx/drivers/include
nRF5SDK153059ac345/nRF5_SDK_15.3.0_59ac345/modules/nrfx/drivers/src
nRF5SDK153059ac345/nRF5_SDK_15.3.0_59ac345/integration/nrfx/legacy

Something interesting in file nrfx_timer.c, looks like a compile time evaluation may determine the size of an array of time_control_block_t types:

   64 static timer_control_block_t m_cb[NRFX_TIMER_ENABLED_COUNT];

. . . sure enough, in ../include/nrfx_timer.h there is an enum whose members are conditionally compiled. Clever!:

enum {
#if NRFX_CHECK(NRFX_TIMER0_ENABLED)
    NRFX_TIMER0_INST_IDX,
#endif
#if NRFX_CHECK(NRFX_TIMER1_ENABLED)
    NRFX_TIMER1_INST_IDX,
#endif
#if NRFX_CHECK(NRFX_TIMER2_ENABLED)
    NRFX_TIMER2_INST_IDX,
#endif
#if NRFX_CHECK(NRFX_TIMER3_ENABLED)
    NRFX_TIMER3_INST_IDX,
#endif
#if NRFX_CHECK(NRFX_TIMER4_ENABLED)
    NRFX_TIMER4_INST_IDX,
#endif
    NRFX_TIMER_ENABLED_COUNT
};