First of all, our loop() function is empty, is the Uno doing nothing? Second, what are all these strange acronyms: OVF, ISR, TCCR1A, etc.?įor starters, here is some more background about the Uno timers. You probably noticed a few weird things here. The following code sets up one of Arduino's hardware timers and uses it to toggle the LED roughly every second: 5 different ways to toggle an LED on Arduino - using hardware timers Uno boards use the ATmega328 microcontroller, and run it with a clock speed of 16 MHz, or 16 million times per second. This interval is usually tied to the clock speed of the microcontroller. Hardware timers in Arduino are simply counters that go up every predetermined interval. However, if we focus just on the Uno board, we can start taking advantage of its specific hardware features - namely, timers and interrupts. Our solutions to blink an LED with Arduino so far relied on Arduino's built-in functions, so they would virtually work on any board supported by the Arduino environment. You can also tinker with this code in the online Arduino simulator: blinking three LEDs without delay() playground. Can you write the code for that? A similar, but more verbose approach can also be found in Arduino's documentation. For example, you can blink three LEDs in different intervals: one every second, one every 1.26 seconds, and one every 380 milliseconds. This solution of not using delay() has a big advantage over the previous approaches to toggle an LED: we can perform additional tasks inside our loop, as it is no longer blocking on the delay() function. This is how we achieve the desired blink. In other words, we repeatedly take the number of seconds passed since the program started running, and set the value of the LED based on that: ON if the number if currently odd, OFF if it is currently even. This calculation returns 0 for even numbers and 1 for odd numbers: Finally, we take the number of seconds and calculate the remainder of dividing it by two, using the modulus ( %) operator. We then divide this value by 1000, so we get the number of seconds passed so far. We take advantage of Arduino's millis() function, which returns the number of milliseconds since the program has started running. The one-liner code to toggle the LED is shown below: 5 ways to blink an LED in Arduino - Using millis() By using a clever trick, we no longer need to call delay() in our code to blink the LED using Arduino. This is my favorite one, which was first presented to me by my friend Avi Ostfeld. So basically the code above could be read as: We use the ! (not) operator to invert that value, and thus toggle the state of the LED. Here's the trick: digitalRead() returns the current output value of the pin: 1 if the pin is high and the LED is on, 0 otherwise. We can easily cut the loop() code in the LED blink program down to two lines by toggling the value of the pin: 5 ways to blink an LED in Arduino - Using Inversion You can try it yourself on the free online Arduino blink code simulator playground.Ĭan we achieve the same with less code? The Two-Liner
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