如何获得beaglebone黑色LED的闪烁频率？

Question

I have the following code which is used to blink USR3 LED of beaglebone black.

var b = require('bonescript');
var led = "USR3";
var state = 0;

b.pinMode(led, 'out');
toggleLED = function() {
    state = state ? 0 : 1;
    b.digitalWrite(led, state);
};

timer = setInterval(toggleLED, 200); //doubling the time to toggle led half as fast

stopTimer = function() {
    clearInterval(timer);
};

setTimeout(stopTimer, 3000);

The time set while calling setTimeout is in milliseconds. So the code works and blinks the led for a certain number of times in 3 seconds (ie 3000 milliseconds.) Is there a way to output this frequency ?

Answer 1

You are defining the frequency by letting the LED toggle ever 200ms. Frequency is defined as 1/period of a full phase of the signal. For a rectangle signal with 0 / 1: ,,,, |''''|,,,,| ''''|,,,, your period is 200ms + 200ms because you toggle every 200ms. Then the frequency is calculated as 1/400ms => 2,5Hz

If this isn't what your looking for, please refine your question.