Low Power Ticker
[Hal]

Get low power ticker's data.

Returns:

The low power ticker data

Definition at line 42 of file mbed_lp_ticker_api.c.

Clear the low power ticker interrupt.

Pseudo Code:

 void lp_ticker_clear_interrupt(void)
 {
     // Write to the ICR (interrupt clear register) of the LPTMR
     LPTMR_ICR = LPTMR_ICR_COMPARE_Msk;
 }

Disable low power ticker interrupt.

Pseudo Code:

 void lp_ticker_disable_interrupt(void)
 {
     // Disable the compare interrupt
     LPTMR_CTRL &= ~LPTMR_CTRL_COMPARE_ENABLE_Msk;
 }

Set pending interrupt that should be fired right away.

Pseudo Code:

 void lp_ticker_fire_interrupt(void)
 {
     NVIC_SetPendingIRQ(LPTMR_IRQn);
 }

Deinitialize the lower power ticker.

Powerdown the lp ticker in preparation for sleep, powerdown, or reset.

After calling this function no other ticker functions should be called except lp_ticker_init(). Calling any function other than init after freeing is undefined.

Note:

This function stops the ticker from counting.

Get frequency and counter bits of this ticker.

Pseudo Code:

 const ticker_info_t* lp_ticker_get_info()
 {
     static const ticker_info_t info = {
         32768,      // 32KHz
         16          // 16 bit counter
     };
     return &info;
 }

Initialize the low power ticker.

Initialize or re-initialize the ticker. This resets all the clocking and prescaler registers, along with disabling the compare interrupt.

Pseudo Code:

 void lp_ticker_init()
 {
     // Enable clock gate so processor can read LPTMR registers
     POWER_CTRL |= POWER_CTRL_LPTMR_Msk;

     // Disable the timer and ensure it is powered down
     LPTMR_CTRL &= ~(LPTMR_CTRL_ENABLE_Msk | LPTMR_CTRL_COMPARE_ENABLE_Msk);

     // Configure divisors - no division necessary
     LPTMR_PRESCALE = 0;
     LPTMR_CTRL |= LPTMR_CTRL_ENABLE_Msk;

     // Install the interrupt handler
     NVIC_SetVector(LPTMR_IRQn, (uint32_t)lp_ticker_irq_handler);
     NVIC_EnableIRQ(LPTMR_IRQn);
 }

The wrapper for ticker_irq_handler, to pass lp ticker's data.

Definition at line 60 of file mbed_lp_ticker_api.c.

Read the current tick.

If no rollover has occurred, the seconds passed since lp_ticker_init() was called can be found by dividing the ticks returned by this function by the frequency returned by lp_ticker_get_info.

Returns:

The current timer's counter value in ticks

Pseudo Code:

 uint32_t lp_ticker_read()
 {
     uint16_t count;
     uint16_t last_count;

     // Loop until the same tick is read twice since this
     // is ripple counter on a different clock domain.
     count = LPTMR_COUNT;
     do {
         last_count = count;
         count = LPTMR_COUNT;
     } while (last_count != count);

     return count;
 }

Set interrupt for specified timestamp.

Parameters:

timestamp

The time in ticks to be set

Note:

no special handling needs to be done for times in the past as the common timer code will detect this and call lp_ticker_fire_interrupt() if this is the case

calling this function with timestamp of more than the supported number of bits returned by lp_ticker_get_info results in undefined behavior.

Pseudo Code:

 void lp_ticker_set_interrupt(timestamp_t timestamp)
 {
     LPTMR_COMPARE = timestamp;
     LPTMR_CTRL |= LPTMR_CTRL_COMPARE_ENABLE_Msk;
 }

Set low power ticker IRQ handler.

Parameters:

ticker_irq_handler

IRQ handler to be connected

Returns:

previous ticker IRQ handler

Note:

by default IRQ handler is set to ticker_irq_handler

this function is primarily for testing purposes and it's not required part of HAL implementation

Definition at line 51 of file mbed_lp_ticker_api.c.