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Ticker

Ticker class hierarchy

Use the Ticker interface to set up a recurring interrupt; it calls a function repeatedly and at a specified rate.

You can create any number of Ticker objects, allowing multiple outstanding interrupts at the same time. The function can be a static function, a member function of a particular object or a Callback object.

Warnings and notes

  • No blocking code in ISR: avoid any call to wait, infinite while loop or blocking calls in general.

  • No printf, malloc or new in ISR: avoid any call to bulky library functions. In particular, certain library functions (such as printf, malloc and new) are not re-entrant, and their behavior could be corrupted when called from an ISR.

  • While an event is attached to a Ticker, deep sleep is blocked to maintain accurate timing. If you don't need microsecond precision, consider using the LowPowerTicker class instead because that does not block deep sleep mode.

Ticker class reference

Public Member Functions
void attach (Callback< void()> func, float t)
 Attach a function to be called by the Ticker, specifying the interval in seconds. More...
template<typename T , typename M >
void attach (T *obj, M method, float t)
 Attach a member function to be called by the Ticker, specifying the interval in seconds. More...
void attach_us (Callback< void()> func, us_timestamp_t t)
 Attach a function to be called by the Ticker, specifying the interval in microseconds. More...
template<typename T , typename M >
void attach_us (T *obj, M method, us_timestamp_t t)
 Attach a member function to be called by the Ticker, specifying the interval in microseconds. More...
void detach ()
 Detach the function. More...
Static Public Member Functions
static void irq (uint32_t id)
 The handler registered with the underlying timer interrupt. More...
Protected Member Functions
void insert (timestamp_t timestamp)
 Set relative timestamp of the internal event. More...
void insert_absolute (us_timestamp_t timestamp)
 Set absolute timestamp of the internal event. More...
void remove ()
 Remove timestamp. More...

Ticker hello, world

Try this program to set up a Ticker to repeatedly invert an LED:

/* mbed Example Program
 * Copyright (c) 2006-2014 ARM Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include "mbed.h"
 
Ticker flipper;
DigitalOut led1(LED1);
DigitalOut led2(LED2);
 
void flip() {
    led2 = !led2;
}
 
int main() {
    led2 = 1;
    flipper.attach(&flip, 2.0); // the address of the function to be attached (flip) and the interval (2 seconds)
 
    // spin in a main loop. flipper will interrupt it to call flip
    while(1) {
        led1 = !led1;
        wait(0.2);
    }
}

Ticker examples

Use this example to attach a member function to a ticker:

#include "mbed.h"
 
// A class for flip()-ing a DigitalOut 
class Flipper {
public:
    Flipper(PinName pin) : _pin(pin) {
        _pin = 0;
    }
    void flip() {
        _pin = !_pin;
    }
private:
    DigitalOut _pin;
};
 
DigitalOut led1(LED1);
Flipper f(LED2);
Ticker t;
 
int main() {
    // the address of the object, member function, and interval
    t.attach(callback(&f, &Flipper::flip), 2.0); 
 
    // spin in a main loop. flipper will interrupt it to call flip
    while(1) {
        led1 = !led1;
        wait(0.2);
    }
}