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Modules | Functions
Microsecond Ticker

Low level interface to the microsecond ticker of a target. More...

Modules

 Microsecond Ticker tests
 Tests to validate the proper implementation of the microsecond ticker.
 
 Ticker Hal
 Low level interface to the ticker of a target.
 
 Ticker Tests
 Tests to validate the proper implementation of a ticker.
 

Functions

ticker_irq_handler_type set_us_ticker_irq_handler (ticker_irq_handler_type ticker_irq_handler)
 Set ticker IRQ handler. More...
 
const ticker_data_tget_us_ticker_data (void)
 Get ticker's data. More...
 
void us_ticker_irq_handler (void)
 The wrapper for ticker_irq_handler, to pass us ticker's data. More...
 
void us_ticker_init (void)
 Initialize the ticker. More...
 
void us_ticker_free (void)
 Deinitialize the us ticker. More...
 
uint32_t us_ticker_read (void)
 Read the current counter. More...
 
void us_ticker_set_interrupt (timestamp_t timestamp)
 Set interrupt for specified timestamp. More...
 
void us_ticker_disable_interrupt (void)
 Disable us ticker interrupt. More...
 
void us_ticker_clear_interrupt (void)
 Clear us ticker interrupt. More...
 
void us_ticker_fire_interrupt (void)
 Set pending interrupt that should be fired right away. More...
 
const ticker_info_tus_ticker_get_info (void)
 Get frequency and counter bits of this ticker. More...
 

Detailed Description

Low level interface to the microsecond ticker of a target.

Defined behavior

Undefined behavior

See also
Microsecond Ticker tests

Function Documentation

const ticker_data_t* get_us_ticker_data ( void  )

Get ticker's data.

Returns
The microsecond ticker data
ticker_irq_handler_type set_us_ticker_irq_handler ( ticker_irq_handler_type  ticker_irq_handler)

Set ticker IRQ handler.

Parameters
ticker_irq_handlerIRQ 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
void us_ticker_clear_interrupt ( void  )

Clear us ticker interrupt.

Pseudo Code:

1 void us_ticker_clear_interrupt(void)
2 {
3  // Write to the ICR (interrupt clear register) of the TIMER
4  TIMER_ICR = TIMER_ICR_COMPARE_Msk;
5 }
void us_ticker_disable_interrupt ( void  )

Disable us ticker interrupt.

Pseudo Code:

1 void us_ticker_disable_interrupt(void)
2 {
3  // Disable the compare interrupt
4  TIMER_CTRL &= ~TIMER_CTRL_COMPARE_ENABLE_Msk;
5 }
void us_ticker_fire_interrupt ( void  )

Set pending interrupt that should be fired right away.

The ticker should be initialized prior calling this function.

Pseudo Code:

1 void us_ticker_fire_interrupt(void)
2 {
3  NVIC_SetPendingIRQ(TIMER_IRQn);
4 }
void us_ticker_free ( void  )

Deinitialize the us ticker.

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

After this function is called, no other ticker functions should be called except us_ticker_init(), calling any function other than init is undefined.

Note
This function stops the ticker from counting.

Pseudo Code:

1 uint32_t us_ticker_free()
2 {
3  // Disable timer
4  TIMER_CTRL &= ~TIMER_CTRL_ENABLE_Msk;
5 
6  // Disable the compare interrupt
7  TIMER_CTRL &= ~TIMER_CTRL_COMPARE_ENABLE_Msk;
8 
9  // Disable timer interrupt
10  NVIC_DisableIRQ(TIMER_IRQn);
11 
12  // Disable clock gate so processor cannot read TIMER registers
13  POWER_CTRL &= ~POWER_CTRL_TIMER_Msk;
14 }
const ticker_info_t* us_ticker_get_info ( void  )

Get frequency and counter bits of this ticker.

Pseudo Code:

1 const ticker_info_t* us_ticker_get_info()
2 {
3  static const ticker_info_t info = {
4  1000000, // 1 MHz
5  32 // 32 bit counter
6  };
7  return &info;
8 }
void us_ticker_init ( void  )

Initialize the ticker.

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

Note
Initialization properties tested by ticker_init_test

Pseudo Code:

1 void us_ticker_init()
2 {
3  // Enable clock gate so processor can read TIMER registers
4  POWER_CTRL |= POWER_CTRL_TIMER_Msk;
5 
6  // Disable the timer and ensure it is powered down
7  TIMER_CTRL &= ~(TIMER_CTRL_ENABLE_Msk | TIMER_CTRL_COMPARE_ENABLE_Msk);
8 
9  // Configure divisors
10  uint32_t prescale = SystemCoreClock / 1000000;
11  TIMER_PRESCALE = prescale - 1;
12  TIMER_CTRL |= TIMER_CTRL_ENABLE_Msk;
13 
14  // Install the interrupt handler
15  NVIC_SetVector(TIMER_IRQn, (uint32_t)us_ticker_irq_handler);
16  NVIC_EnableIRQ(TIMER_IRQn);
17 }
void us_ticker_irq_handler ( void  )

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

uint32_t us_ticker_read ( void  )

Read the current counter.

Read the current counter value without performing frequency conversions. If no rollover has occurred, the seconds passed since us_ticker_init() was called can be found by dividing the ticks returned by this function by the frequency returned by us_ticker_get_info.

Returns
The current timer's counter value in ticks

Pseudo Code:

1 uint32_t us_ticker_read()
2 {
3  return TIMER_COUNT;
4 }
void us_ticker_set_interrupt ( timestamp_t  timestamp)

Set interrupt for specified timestamp.

Parameters
timestampThe 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 us_ticker_fire_interrupt() if this is the case
calling this function with timestamp of more than the supported number of bits returned by us_ticker_get_info results in undefined behavior.

Pseudo Code:

1 void us_ticker_set_interrupt(timestamp_t timestamp)
2 {
3  TIMER_COMPARE = timestamp;
4  TIMER_CTRL |= TIMER_CTRL_COMPARE_ENABLE_Msk;
5 }
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