TIMER module

About this

This module contains functions for accessing the hardware timers, and include delays in your programs. The functions of this module are organized in the following categories:

• Delay functions
• Hardware timers
• Software timers

Delay functions

The delay functions introduces a delay in the program for a specified period of time. The delay is executed in the current thread, and no context switch is done, at least until the next context switch scheduled by Lua RTOS.

tmr.delay(seconds)

Waits for the specified seconds, then returns.

Arguments:

• seconds: number of seconds to wait.

Returns: nothing, or an exception.

tmr.delayms(milliseconds)

Waits for the specified milliseconds, then returns.

Arguments:

• milliseconds: number of milliseconds to wait.

Returns: nothing, or an exception.

tmr.delayus(microseconds)

Waits for the specified microseconds, then returns.

Arguments:

• microseconds: number of microseconds to wait.

Returns: nothing, or an exception.

Sleep functions

The sleep functions suspend the program's execution for a specified period of time by suspending the current thread.

tmr.sleep(seconds)

Sleeps for the specified seconds, then returns.

Arguments:

• seconds: number of seconds to sleep.

Returns: nothing, or an exception.

tmr.sleepms(milliseconds)

Sleeps for the specified milliseconds, then returns.

Arguments:

• milliseconds: number of milliseconds to sleep.

Returns: nothing, or an exception.

tmr.sleepus(microseconds)

Sleeps for the specified microseconds, then returns.

Arguments:

• microseconds: number of microseconds to sleep.

Returns: nothing, or an exception.

Hardware timers

instance = tmr.attach(id, period, callback)

Attach a hardware timer, calling a callback at regular intervals defined by the period argument. The timer is reloaded automatically after calling the callback.

Arguments:

• id: the timer id. Can be either tmr.TMR0, tmr.TMR1, tmr.TMR2, or tmr.TMR3.
• period: the timer's period in microseconds.
• callback: the call back function to call when the timer expires.

Returns: the timer instance, or an exception. You must store the timer instance into a variable for further operations with it.

instance:detach()

Detach a hardware timer, and free all resources used by timer.

Arguments: nothing. Returns: nothing, or an exception.

instance:start()

Start the timer.

Arguments: noting. Returns: nothing, or an exception.

instance:stop()

Stop the timer.

Arguments: noting. Returns: nothing, or an exception.

Full example

This example use a hardware timer for blink a led every 50 milliseconds

-- Blink function
function blink()
   if (led_on) then
      pio.pin.sethigh(pio.GPIO26)
      led_on = false
   else
      pio.pin.setlow(pio.GPIO26)
      led_on = true
   end
end

-- Configure the GPIO where the led is attached
pio.pin.setdir(pio.OUTPUT, pio.GPIO26)

-- Variable for store the led status
led_on = false

-- Attach the timer. 50 milliseconds = 50000 micro seconds
t0 = tmr.attach(tmr.TMR0, 50000, blink)

-- Start the timer (the led blinks)
t0:start()

...

-- Stop the timer
t0:stop()

Software timers

instance = tmr.attach(period, callback)

Attach a software timer, calling a callback at regular intervals defined by the period argument. The timer is reloaded automatically after calling the callback.

Arguments:

• period: the timer's period in milliseconds.
• callback: the call back function to call when the timer expires.

Returns: the timer instance, or an exception. You must store the timer instance into a variable for further operations with it.

instance:detach()

Detach a software timer, and free all resources used by timer.

Arguments: nothing. Returns: nothing, or an exception.

instance:start()

Start the timer.

Arguments: noting. Returns: nothing, or an exception.

instance:stop()

Stop the timer.

Arguments: noting. Returns: nothing, or an exception.

Full example

This example use a software timer for blink a led every 50 milliseconds

-- Blink function
function blink()
   if (led_on) then
      pio.pin.sethigh(pio.GPIO26)
      led_on = false
   else
      pio.pin.setlow(pio.GPIO26)
      led_on = true
   end
end

-- Configure the GPIO where the led is attached
pio.pin.setdir(pio.OUTPUT, pio.GPIO26)

-- Variable for store the led status
led_on = false

-- Attach the timer
t0 = tmr.attach(50, blink)

-- Start the timer (the led blinks)
t0:start()

...

-- Stop the timer
t0:stop()