Low-level RTT (Real Time Timer) peripheral driver. More...

Detailed Description

Low-level RTT (Real Time Timer) peripheral driver.

(Low-) Power Implications

After the RTT has been initialized (i.e. after calling rtt_init()), the RTT should be powered on and running. The RTT can then be powered off manually at a later point in time by calling the rtt_poweroff() function. When the RTT is powered back on using the rtt_poweron() function, it should transparently continue its previously configured operation.

On many CPUs, certain power states might need to be blocked in rtt_init(), so that it is ensured that the RTT will function properly while it is enabled.

Files
file	rtt.h
	Low-level RTT (Real Time Timer) peripheral driver interface definitions.

Macros
#define	RTT_FREQUENCY
	The desired frequency for the RTT.

#define	RTT_MAX_VALUE
	The maximum value for the RTT counter, must be (2^n - 1)

#define	RTT_MIN_OFFSET (2U)
	The minimum offset to correctly set an rtt callback. More...

#define	RTT_US_TO_TICKS(us) (RTT_SEC_TO_TICKS(us) / 1000000UL)
	Convert microseconds to rtt ticks. More...

#define	RTT_MS_TO_TICKS(ms) (RTT_SEC_TO_TICKS(ms) / 1000UL)
	Convert milliseconds to rtt ticks. More...

#define	RTT_SEC_TO_TICKS(sec) (sec * RTT_FREQUENCY)
	Convert seconds to rtt ticks. More...

#define	RTT_MIN_TO_TICKS(min) (RTT_SEC_TO_TICKS((min) * 60))
	Convert minutes to rtt ticks. More...

#define	RTT_TICKS_TO_US(ticks) ((uint64_t)(ticks) * 1000000UL / RTT_FREQUENCY)
	Convert rtt ticks to microseconds. More...

#define	RTT_TICKS_TO_MS(ticks) (RTT_TICKS_TO_US(ticks) / 1000)
	Convert rtt ticks to milliseconds. More...

#define	RTT_TICKS_TO_SEC(ticks) (RTT_TICKS_TO_MS(ticks) / 1000)
	Convert rtt ticks to seconds. More...

#define	RTT_TICKS_TO_MIN(ticks) (RTT_TICKS_TO_SEC(ticks) / 60)
	Convert rtt ticks to minutes. More...

Typedefs
typedef void(*	rtt_cb_t) (void *arg)
	Signature for the alarm callback. More...

Functions
void	rtt_init (void)
	Initialize RTT module.

void	rtt_set_overflow_cb (rtt_cb_t cb, void *arg)
	Set a callback for the counter overflow event. More...

void	rtt_clear_overflow_cb (void)
	Clear the overflow callback.

uint32_t	rtt_get_counter (void)
	Get the current RTT counter. More...

void	rtt_set_counter (uint32_t counter)
	Set the RTT counter to a specified value. More...

void	rtt_set_alarm (uint32_t alarm, rtt_cb_t cb, void *arg)
	Set an alarm for RTT to the specified absolute target time. More...

uint32_t	rtt_get_alarm (void)
	Get the value of a set alarm. More...

void	rtt_clear_alarm (void)
	Clear any set alarm, do nothing if nothing set.

void	rtt_poweron (void)
	Turn the RTT hardware module on.

void	rtt_poweroff (void)
	Turn the RTT hardware module off.

Macro Definition Documentation

◆ RTT_MIN_OFFSET

#define RTT_MIN_OFFSET (2U)

The minimum offset to correctly set an rtt callback.

If the callback is taking into account rtt_get_counter() then the rtt might advance right between the call to rtt_get_counter() and rtt_set_alarm(). If that happens with val==1, the alarm would be set to the current time, which would then underflow. To avoid this, the alarm should be set at least two ticks in the future.

This value can vary depending on the platform.

Definition at line 79 of file rtt.h.

◆ RTT_MIN_TO_TICKS

#define RTT_MIN_TO_TICKS ( min ) (RTT_SEC_TO_TICKS((min) * 60))

Convert minutes to rtt ticks.

Parameters

[in] min number of minutes

Returns: rtt ticks

Definition at line 130 of file rtt.h.

◆ RTT_MS_TO_TICKS

#define RTT_MS_TO_TICKS ( ms ) (RTT_SEC_TO_TICKS(ms) / 1000UL)

Convert milliseconds to rtt ticks.

Parameters

[in] ms number of milliseconds

Returns: rtt ticks

Definition at line 116 of file rtt.h.

◆ RTT_SEC_TO_TICKS

#define RTT_SEC_TO_TICKS ( sec ) (sec * RTT_FREQUENCY)

Convert seconds to rtt ticks.

Parameters

[in] sec number of seconds

Returns: rtt ticks

Definition at line 123 of file rtt.h.

◆ RTT_TICKS_TO_MIN

#define RTT_TICKS_TO_MIN ( ticks ) (RTT_TICKS_TO_SEC(ticks) / 60)

Convert rtt ticks to minutes.

Parameters

[in] ticks rtt ticks

Returns: number of minutes

Definition at line 158 of file rtt.h.

◆ RTT_TICKS_TO_MS

#define RTT_TICKS_TO_MS ( ticks ) (RTT_TICKS_TO_US(ticks) / 1000)

Convert rtt ticks to milliseconds.

Parameters

[in] ticks rtt ticks

Returns: number of milliseconds

Definition at line 144 of file rtt.h.

◆ RTT_TICKS_TO_SEC

#define RTT_TICKS_TO_SEC ( ticks ) (RTT_TICKS_TO_MS(ticks) / 1000)

Convert rtt ticks to seconds.

Parameters

[in] ticks rtt ticks

Returns: number of seconds

Definition at line 151 of file rtt.h.

◆ RTT_TICKS_TO_US

#define RTT_TICKS_TO_US ( ticks ) ((uint64_t)(ticks) * 1000000UL / RTT_FREQUENCY)

Convert rtt ticks to microseconds.

Parameters

[in] ticks rtt ticks

Returns: number of microseconds

Definition at line 137 of file rtt.h.

◆ RTT_US_TO_TICKS

#define RTT_US_TO_TICKS ( us ) (RTT_SEC_TO_TICKS(us) / 1000000UL)

Convert microseconds to rtt ticks.

Parameters

[in] us number of microseconds

Returns: rtt ticks

Definition at line 109 of file rtt.h.

Typedef Documentation

◆ rtt_cb_t

typedef void(* rtt_cb_t) (void *arg)

Signature for the alarm callback.

Parameters

[in] arg Optional argument which is passed to the callback

Definition at line 166 of file rtt.h.

Function Documentation

◆ rtt_get_alarm()

uint32_t rtt_get_alarm ( void )

Get the value of a set alarm.

If no alarm is set, the return value is arbitrary.

Returns: Value the alarm is set to

◆ rtt_get_counter()

uint32_t rtt_get_counter ( void )

Get the current RTT counter.

Returns: Current value of the RTT counter

◆ rtt_set_alarm()

void rtt_set_alarm	(	uint32_t	alarm,
		rtt_cb_t	cb,
		void *	arg
	)

Set an alarm for RTT to the specified absolute target time.

Parameters

[in]	alarm	The value to trigger an alarm when hit
[in]	cb	Callback executed when alarm is hit
[in]	arg	Argument passed to callback when alarm is hit

◆ rtt_set_counter()

void rtt_set_counter ( uint32_t counter )

Set the RTT counter to a specified value.

Parameters

[in] counter The value to set the RTT to.

◆ rtt_set_overflow_cb()

void rtt_set_overflow_cb	(	rtt_cb_t	cb,
		void *	arg
	)

Set a callback for the counter overflow event.

Parameters

[in]	cb	Callback to execute on overflow
[in]	arg	Argument passed to the callback

Detailed Description

(Low-) Power Implications

Files

Macros

Typedefs

Functions

Macro Definition Documentation

◆ RTT_MIN_OFFSET

◆ RTT_MIN_TO_TICKS

◆ RTT_MS_TO_TICKS

◆ RTT_SEC_TO_TICKS

◆ RTT_TICKS_TO_MIN

◆ RTT_TICKS_TO_MS

◆ RTT_TICKS_TO_SEC

◆ RTT_TICKS_TO_US

◆ RTT_US_TO_TICKS

Typedef Documentation

◆ rtt_cb_t

Function Documentation

◆ rtt_get_alarm()

◆ rtt_get_counter()

◆ rtt_set_alarm()

◆ rtt_set_counter()

◆ rtt_set_overflow_cb()