Timer

Low-level timer peripheral driver.

unsigned int tim_t

Default timer type.

We chose the name of tim_t here to avoid naming clashes with other libraries and vendor device header.

void(* timer_cb_t()

Signature of event callback functions triggered from interrupts.

Parameters

arg:optional context for the callback
channel:timer channel that triggered the interrupt

int timer_init(drivers/include/periph/timer.h::tim_t dev, unsigned long freq, drivers/include/periph/timer.h::timer_cb_t cb, void * arg)

Initialize the given timer.

Each timer device is running with the given speed. Each can contain one or more channels as defined in periph_conf.h. The timer is configured in up-counting mode and will count until TIMER_x_MAX_VALUE as defined in used board’s periph_conf.h until overflowing.

The timer will be started automatically after initialization with interrupts enabled.

Parameters

dev:the timer to initialize
freq:requested number of ticks per second
cb:this callback is called in interrupt context, the emitting channel is passed as argument
arg:argument to the callback

Return values

  • 0 on success
  • -1 if speed not applicable or unknown device given
int timer_set(drivers/include/periph/timer.h::tim_t dev, int channel, unsigned int timeout)

Set a given timer channel for the given timer device.

The callback given during initialization is called when timeout ticks have passed after calling this function

Parameters

dev:the timer device to set
channel:the channel to set
timeout:timeout in ticks after that the registered callback is executed

Return values

  • 1 on success
  • -1 on error
int timer_set_absolute(drivers/include/periph/timer.h::tim_t dev, int channel, unsigned int value)

Set an absolute timeout value for the given channel of the given timer.

Parameters

dev:the timer device to set
channel:the channel to set
value:the absolute compare value when the callback will be triggered

Return values

  • 1 on success
  • -1 on error
int timer_clear(drivers/include/periph/timer.h::tim_t dev, int channel)

Clear the given channel of the given timer device.

Parameters

dev:the timer device to clear
channel:the channel on the given device to clear

Return values

  • 1 on success
  • -1 on error
unsigned int timer_read(drivers/include/periph/timer.h::tim_t dev)

Read the current value of the given timer device.

Parameters

dev:the timer to read the current value from

Return values

  • the timers current value
void timer_start(drivers/include/periph/timer.h::tim_t dev)

Start the given timer.

This function is only needed if the timer was stopped manually before.

Parameters

dev:the timer device to start

void timer_stop(drivers/include/periph/timer.h::tim_t dev)

Stop the given timer.

This will effect all of the timer’s channels.

Parameters

dev:the timer to stop

TIMER_DEV( x)

Default timer definition macro. 

1
(x)

remove dev_enums.h include once all platforms are ported to the updated periph interface

Overwrite this in your CPUs periph_cpu.h file if needed

TIMER_UNDEF

Default value for timer not defined. 

1
(UINT_MAX)
struct timer_isr_ctx_t

Default interrupt context entry holding callback and argument.

drivers/include/periph/timer.h::timer_cb_t cb

callback executed from timer interrupt

void * arg

optional argument given to that callback