![]() ![]() The I/O port registers are defined in Section 14.4, page 100, in the ATmega328P Datasheet: DDRB = DDRB | 1CLKCTRL.reg = GCLK_CLKCTRL_CLKEN | The first step is to use the Data Direction Register to define this pin as an output. For this example you'll need to connect an LED in series with a 220Ω resistor between pin 10 and GND:Ĭonnecting an LED to the Arduino Uno or Arduino Zero to be blinked by a timer. In these examples we have to deal with the fact that the microcontroller uses one system of numbering I/O pins, grouping the pins into ports, but the Arduino board numbers the pins using consecutive integers.įor this example we'll use Arduino pin 10, which is bit 2 in port B. Timer/Counter1 is hardwired to generate waveforms on the following two I/O lines: Timer/Counter0 is used for millis() and Timer/Counter2 is used for tone(), so this example uses the 16-bit Timer/Counter1. The ATmega328P has three Timer/Counter peripherals. AVRįor the AVR version of the Blink example I'll use the ATmega328P on the Arduino Uno. ![]() If you're using Safari the link will just open the datasheet at the first page, and you'll have to scroll to the correct page in the datasheet manually alternatively, copy and paste the URL into the address bar of another browser. ![]() Note that these page links work on most browsers, but unfortunately not on Safari. In the following descriptions I include links to the appropriate page in each datasheet. This is a good way of quickly setting up a source of a square wave with a precise frequency.įiguring out how to program peripherals directly, rather than using the Arduino functions, typically involves a lot of digging into the appropriate microcontroller datasheet. Also, because there's no overhead from executing the interrupt it's capable of generating higher frequencies, typically up to about half the clock frequency. The advantage of the second approach is that it's simpler, and the output waveform will be precise, with no jitter due to the time taken to respond to the interrupt. The other way, which is the way I'll use, is to configure the timer to directly toggle an output pin.One way is to use the timer to generate a regular interrupt, and then toggle the I/O line in the interrupt service routine.Like the original Arduino Blink example the LED will be flashed at exactly 0.5Hz one second on and one second off. In this example I'm going to use a timer to toggle an LED connected to an I/O pin. Most microcontrollers include one or more timer peripherals that allow you to time precise intervals and generate waveforms on output pins. I thought it would be an interesting exercise to compare how you approach the same task on AVR and ARM processors, and the programs will work on most other boards based on the same processors. The Arduino Uno, based on the AVR ATmega328P, and the Arduino Zero, This article compares how you can configure a timer to blink an LED, or generate a waveform, on the ATmega328P microcontroller on the Arduino Uno, and the ATSAMD21 microcontroller on the Arduino Zero: Using a Timer on the Arduino Uno or Arduino Zero ![]()
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