*/ĭue to the speed of execution interrupts can be used for setting up clocks for data lines (I2C for example), or to configure LED fading or any other number of time specific events or communications. * Nothing to do all is done by hardware. MyTim->attachInterrupt(Update_IT_callback) MyTim->setOverflow(10, HERTZ_FORMAT) // 10 Hz HardwareTimer *MyTim = new HardwareTimer(Instance) Thanks to 'new' instanciation, HardwareTimer is not destructed when setup() function is finished. The PWM function can also be used to achieve this in one line of code (if a simple LED On/Off Operation) #if defined(LED_BUILTIN) This and more examples for the STM32Duino core can be found at this GitHub Repository. TimerAttachInterrupt(timer, &onTime, true) ![]() Configure Prescaler to 80, as our timer runs 80Mhz PortMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED TIM_LOOPđ //on interrupt the counter will start with the same value again TIM_SINGLEĐ //on interrupt routine you need to write a new value to start the timer again Timer1_enable(TIM_DIV16, TIM_EDGE, TIM_SINGLE) Timer1_attachInterrupt(onTime) // Add ISR Function Prescaler can equal the below values and needs the relevant bits setting (timer speed(Hz)) = (Arduino clock speed(16MHz)) / prescaler compareMatchReg = - 1ĬompareMatchReg = - 1ĬompareMatchReg = - 1 = 15624Īs this is > 256 Timer 1 Must be used for this.ĬompareMatchReg = 15624 // preload timer from calc above Set compareMatchReg to the correct value for our interrupt interval ! Remember ! that when you use timers 0 and 2 this number must be less than 256, and less than 65536 for timer1 The prescaler allows this to be scaled to allow longer intervals.įor AVR boards the compare match register also needs configuring, and is worked through in the code below fully.Ĭompare match register = - 1 The prescaler is used, as the timers can only store up to 8/16 bits in their counters, meaning they would overflow every 256/16000000 s (16us) for 8 bit counters, and 65536 / 16000000 s (4us) for 16 bit counters, which is often far more than needed. The ISR is then configured to fire after a specific number of ticks. The prescaler / divider is what the above frequency is divided by to form a "tick" of the timer (increment its counter). Timer speed (Hz) = Timer clock speed (Mhz) / prescaler These vary board to board, and some common boards are listed below: The Mega boards have Timers 3,4,5 which may be used instead CalculationsĪs these timers are hardware based, all timing is related to the clock of the timer. Timer2 - An 8 bit timer used by the Tone() library Timer1 - A 16 bit timer used by the Servo() library ![]() Timer0 - An 8 bit timer used by Arduino functions delay(), millis() and micros(). NOTE - Timer interrupts may interfere with other functionality (PWM for example) depending on the timer chosen to configure.Ġ (Used by WiFi), 1 is available to configure.Į.g.
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