![]() Simple, right?įirst, let's look at the pseudo-code required to drive this example: We'll create a simple program to flash a LED at about 20Hz. ![]() To start off, we will deal with basic timer functionality and move on from there. In the sections dealing with toggling a LED, it is assumed to be connected to PORTB, bit 0 of your chosen AVR (pin 1 of DIP AVRMEGA16). As modern AVRs come running off their internal ~1MHz RC oscillator by default, you can use this without a problem (although do keep in mind the resultant timing measurements will be slightly incorrect due to the RC frequency tolerance). This is a nicely featured AVR containing certain timer functionality we'll need later on. 45 seconds.įor this tutorial, I will assume the target to be a MEGA16, running at at 1MHz clock. If we measure a delay to be 45 timer periods, then our total delay will be 45 times. 01 seconds - so our timer will measure in multiples of this. As each clock pulse increments the timer's counter by one, the timer measures intervals in periods of one on the input frequency:įor the above example, our period becomes. Like all digital systems, the timer requires a clock in order to function. One thing that trips those new to the AVR timer is the clock source. Timers can be configured to produce outputs directly to pre-determined pins, reducing the processing load on the AVR core. ![]() This is a fancy way of saying that the timers are separate circuits on the AVR chip which can run independent of the main program, interacting via the control and count registers, and the timer interrupts. The AVR timers are very useful as they can run asynchronous to the main AVR core. ![]() AVR timers do a similar job, measuring a given time interval. A simple clock will time the seconds, minutes and hours elapsed in a given day - or in the case of a twelve hour clock, since the last half-day. ![]() We use timers every day - the most simple one can be found on your wrist. However, despite the surface complexity, the function of the timer subsystem can be condensed into one obvious function: to time. They have a myriad of uses ranging from simple delay intervals right up to complex PWM (more on this later) generation. The timer systems on the AVR series of Microcontrollers are complex beasts. What are they, and what can they do for us? For an updated version of this tutorial in PDF format, please see this page of my website.Īt last! Yet another tutorial, this one covering a topic which is the main source of frustration to those new with AVRs timers. ![]()
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January 2023
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