Saturday, July 23, 2022

[SOLVED] Node.js: how can I delay (not sleep) from one line to another to pulse stepper motor in a loop

Issue

I'm controlling a stepper motor with onoff in a Raspberry Pi 3B+ and want to delay between setting pulse high and then low within a loop.

for (i=0; i < steps; i++) {
  pinPul.writeSync(1);
  delay here 10 milliseconds
  pinPul.writeSync(0);
  delay another 10 milliseconds
}

I don't want to stop the execution of any of the other stuff that's going on in the program during the delay.


Solution

Node.js uses a event loop. And you want to use sync functions that waits.

The default approach in js/node is using setTimeout() but it relies on callbacks and cannot be used on a for loop. To fix this you need to use the modern async/await.

async function sleep(ms) {
  return new Promise(resolve => {
    setTimeout(resolve, ms);
  });
}

async function ledLoop() {
  for (i=0; i < steps; i++) {
    pinPul.writeSync(1);
    await sleep(10);
    pinPul.writeSync(0);
    await sleep(10);
  }
}

ledLoop();

Just a comment. 10ms is too fast for the human eye. Change to 1000ms for better testing.



Answered By - Gustavo Garcia
Answer Checked By - David Goodson (WPSolving Volunteer)
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