Connect and share knowledge within a single location that is structured and easy to search. I know that Update in Unity3D runs every frame per second but I because I'm not an electronics guy I don't know how loop function runs on Arduino. Does it depends on number of CPU cycles or micro processor chip in case of Arduino or what? Please explain. I facing some lags in my game. I can fix them only if know how is loop function running on Arduino.
There ain't a lot of information about loop in arduino documentation. Instructions in a CPU run sequentially. The more instructions there are the longer it takes to run.
Also note that many external factors can affect how long loop takes to run - such as serial communication speed, etc. Though in reality there is some setup done before init to make millis and such work. Inspection of HardwareSerial. This means that you can write your own infinite loop within loop perfectly safely, unless you have written serialEvent code and are expecting it to run regularly.
This begs the question: if serialEvent is called sequentially with loop , will serialEvent be called if loop never returns? In other words, is serialEvent interrupt-driven as well as being called when loop returns? A quick test -see below- shows that it is not interrupt-driven, so the previous paragraph is true.
By the way, the internal clock is very slightly off and varies with room temperature, so don't rely on it staying synchronised to your other device without a handshake. He calculated the speed of the loop to be kHz even though the microcontroller has a 16 MHz clock. Sign up to join this community.
The best answers are voted up and rise to the top. Ignore the loop for now, and focus on the digitalWrite line. There are three steps to taking a time measurement:. If we know what time something finishes and what time it started, we can work out how long it took.
In more technical terms, if we subtract the start time from the finish time, the result is the duration. We can use this to initialize a variable. That will show us a rough duration in microseconds. If we run the code, we can see that the result is 8 microseconds. Arduino clock cycles are a much more precise way to measure the speed of a program.
You can think of it as the metronome that orchestrates all the parts of the microcontroller and makes sure everything works in sync. Briefly, our Arduino has three different timers numbered 0, 1 and 2. Timers 0 and 2 count from 0 to , but timer 1 goes all the way to ! These numbers represent the clock cycles that these timers use to keep track of time.
We can change how fast the timers count by setting some configuration bits in one of the control registers. Specifically, we can choose to count every clock cycle, or every 8, 64, , or cycles. Since we want to start counting from zero, we set the counter to zero at the beginning, like this:.
So you set the initial value of the variable, the condition to exit the loop testing the variable , and the action on the variable each time around the loop. The other important point about for-loops is that they need a loop control variable - in the example this is the variable i. This is used as a loop counter and is used to decide when to exit the loop. First of all the variable 'i' is created if it does not already exist and set to zero.
Next the loop variable is tested. Here, if it is smaller than 10 then carry on - otherwise the loop is exited. So the for-loop executes the code "Serial. Notice how there are two statements - ending in semicolons and both are enclosed by curly braces. Compare this to the previous example that used only one statement ending in a semi-colon.
Q: Here's the same question for you. What is the value of i after the loop has finished executing? The reason that you start with the control loop variable at zero is that arrays are defined starting from index zero. If you don't use zero as an initial starting point then you can get an off by one error - meaning you can write to a array location that does not exist.
For an array of 10 values only indices Here's an example of setting up an array initialising each element with a random number. Then printing out the array values in turn. The standard form of the for loop initialises the control variable to 0. For exiting the loop the condition tests whether the variable is smaller than the number of loops needed. You don't have to use this but it makes life easier when dealing with arrays.
Good point. If you unroll the loop a little, you can get intervals of full-speed LED blinking: Here's my test program, no assembly language required:. Saleae logic analyzer screenshot. Wow -- Thank you, Steve and everyone else! This is great community grassroots work. One example is what is inside the main.
I agree that a straight PORTB memory write is probably the most efficient -- but, who's going to remember how which bit to shift? And moreover -- how often do our student need this speed? If you know the pins at compile time, it lets you toggle them on or off in as little as 2 clock cycles. The fastest, but least convenient method, is direct assembly commands. I think one reason you aren't seeing anything close to 16 MHz, is that each call to digitalWrite is not one instruction , but rather one call to a function.
That list could be tens of instructions long or more. Any other thoughts? Compiler inserting ASM commands that are unnecessary. You'll have something slower, but not in uS. This is a use case that they teach in college on MCUs and compilers. Not useful for much, but interesting. The other thing that is important to note and the tests dis not yet demonstrate was not that the low was taking longer, but that the internal loop command is also taking time in the Arduino which is why the other people here are adding a seemingly redundant while 1.
That's exactly right. As for how many instructions are being called, I haven't dug in that far.
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