Public functions to interact with the SysTick driver. More...

Collaboration diagram for SysTick Public API:

Functions
ERR_te	systick_init (SYSTICK_CFG_ts const *systick_cfg)
	Initializes and starts the SysTick timer.
void	systick_deinit (void)
	Deinitializes the SysTick timer.
void	systick_get_def_cfg (SYSTICK_CFG_ts *systick_cfg_o)
	Populates a configuration structure with the default SysTick settings.
uint32_t	systick_get_ms (void)
	Returns the number of milliseconds elapsed since SysTick was initialized.

Detailed Description

Public functions to interact with the SysTick driver.

Function Documentation

◆ systick_init()

ERR_te systick_init ( SYSTICK_CFG_ts const * systick_cfg )

Initializes and starts the SysTick timer.

Computes the reload value from the current AHB clock frequency to achieve a 1 ms tick period, configures the clock source and interrupt settings, clears the current value register, and enables the counter.

Parameters

[in] systick_cfg Pointer to the SysTick configuration structure.

Returns

ERR_OK on success
ERR_MODULE_ALREADY_INITIALIZED if SysTick is already initialized
ERR_UNKNOWN if the computed reload value is zero or exceeds the 24-bit maximum (0xFFFFFF), indicating an unsupported clock frequency

Note: Typically called indirectly via init_systick.

See also: systick_init

Definition at line 41 of file arm_cortex_m4_systick.c.

                                                       {
    if(internal_state.initialized) {
        return ERR_MODULE_ALREADY_INITIALIZED;
    }
 
    // Disable SysTick before reconfiguring
    SYSTICK->SYST_CSR &= ~(1U << SYST_CSR_ENABLE);
 
    // Clear internal state
    internal_state = (struct internal_state_s){ 0 };
 
    // Configure interrupt enable
    SYSTICK->SYST_CSR &= ~(1U << SYST_CSR_TICKINT);
    SYSTICK->SYST_CSR |= (systick_cfg->interrupt << SYST_CSR_TICKINT);
 
    // Configure clock source
    SYSTICK->SYST_CSR &= ~(1U << SYST_CSR_CLKSOURCE);
    SYSTICK->SYST_CSR |= (systick_cfg->clk_source << SYST_CSR_CLKSOURCE);
 
    // Clear current value
    SYSTICK->SYST_CVR = 0;
 
    // Compute reload value for a 1 ms tick period from the AHB clock
    uint32_t cpu_clk = rcc_get_ahb_clk();
    uint32_t one_ms_clk_cycle = cpu_clk / 1000;
    uint32_t reload_value = one_ms_clk_cycle + 1;
    if (reload_value == 0 || reload_value > 0x01000000U) {
        return ERR_UNKNOWN;
    }
 
    // Set reload value (24-bit register)
    SYSTICK->SYST_RVR &= ~(0xFFFFFF);
    SYSTICK->SYST_RVR |= (reload_value - 1);
 
    // Enable SysTick
    SYSTICK->SYST_CSR |= (1U << SYST_CSR_ENABLE);
 
    internal_state.initialized = true;
 
    return ERR_OK;
}

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◆ systick_deinit()

void systick_deinit ( void )

Deinitializes the SysTick timer.

Disables the counter, clears the interrupt and clock source configuration, resets the reload and current value registers, and resets the internal state. Does nothing if SysTick has not been initialized.

See also: systick_deinit

Definition at line 84 of file arm_cortex_m4_systick.c.

                          {
    if(!internal_state.initialized) {
        return;
    }
 
    SYSTICK->SYST_CSR &= ~(1U << SYST_CSR_ENABLE);
 
    internal_state = (struct internal_state_s){ 0 };
 
    SYSTICK->SYST_CSR &= ~(1U << SYST_CSR_TICKINT);
    SYSTICK->SYST_CSR &= ~(1U << SYST_CSR_CLKSOURCE);
 
    SYSTICK->SYST_CVR = 0;
 
    SYSTICK->SYST_RVR &= ~(0xFFFFFF);
}

◆ systick_get_def_cfg()

void systick_get_def_cfg ( SYSTICK_CFG_ts * systick_cfg_o )

Populates a configuration structure with the default SysTick settings.

Default configuration:

Clock source: processor (AHB) clock
Interrupt: enabled

Parameters

[out] systick_cfg_o Pointer to the configuration structure to populate.

See also: systick_get_def_cfg

Definition at line 102 of file arm_cortex_m4_systick.c.

                                                        {
    systick_cfg_o->clk_source = SYSTICK_CLK_SOURCE_PROCESSOR;
    systick_cfg_o->interrupt = SYSTICK_IT_TRUE;
}

◆ systick_get_ms()

uint32_t systick_get_ms ( void )

Returns the number of milliseconds elapsed since SysTick was initialized.

The counter is incremented by the SysTick exception handler on each 1 ms wrap. Returns 0 if SysTick has not been initialized.

Returns: Elapsed time in milliseconds since systick_init was called.

Note: The counter is a 32-bit unsigned value and will wrap after approximately 49.7 days of continuous operation.

See also: systick_get_ms

Definition at line 108 of file arm_cortex_m4_systick.c.

                              {
    if(!internal_state.initialized) {
        return 0;
    }
 
    return internal_state.elapsed_ms;
}