waveform and setInterval issue...

[espruino-discuss]

Posted at 2015-04-12 by d0773d

I've been demoing out different ways to use waveform and come across an issue when using both setInterval and Waveform. the issue is: I am not seeing my temp output in the console.

Code:

var w = new Waveform(128/* your buffer size */,{doubleBuffer:false, bits:16});
setInterval(function() {
  var myarr = w.buffer;
  myarr.sort();
  // cut off first and last 2 elements
  var view = new Uint16Array(myarr.buffer, 2/*sizeof(uint16)*/*2, n-4);
  var vOut = E.getAnalogVRef() * E.sum(view)/(view.length*65536); // if you attached VOUT to Ao
  var vZero = 0.4;
  var tCoeff = 19.5 / 1000;
  var tempinc = (vOut - vZero) / tCoeff;
  var tempinf = tempinc * (9 / 5) + 32;
  console.log("Temp in C: " + tempinc);
  console.log("Temp in F: " + tempinf);
  //console.log(E.sum(view)/(view.length*6­­5536));
  // start it again
  w.startInput(A0,2000 /* Samples per second */);
}, 1000*150/2000 /* so slightly over the 128/2000 sec required for the waveform*/);

I tried setting the time higher, but I am still getting the same issue. I did, however, place a console.log ("start!") Inside of the startInterval as the first line and start! was sent to the Console successfully.

[espruino-discuss]

Posted at 2015-04-12 by d0773d

Ahh crap, my code isn't formatted correct in the forum. Sorry! Im
using my cell phone to post. I have no idea how to fix the
formatting......

Nvm l, I fixed the formatting problem....

[gfwilliams]

Posted at 2015-04-12 by @gfwilliams

Ahh - that's interesting. Looks like there are 2 issues (Which I should have checked!)

• If you make a Uint16Array with everything the same value and then sort it, sort crashes(!) Uint8Array works fine though, and strangely it also works on a Pico! I've just filed a bug for this.
• We need to set a longer interval. As we do all out calculations first, and then kick off the Waveform, the waveform isn't finished by the time the interval fires again. I've just increased the interval to 200ms and that's fixed it.

var w = new Waveform(128/* your buffer size */,{doubleBuffer:false, bits:16});

var first = true;
setInterval(function() {
  if (!first) {
    var myarr = w.buffer;
    myarr.sort();
    // cut off first and last 2 elements
    var view = new Uint16Array(myarr.buffer, 2/*sizeof(uint16)*/*2, myarr.length-4);
    var vOut = E.getAnalogVRef() * E.sum(view)/(view.length*65536); // if you attached VOUT to Ao
    var vZero = 0.4;
    var tCoeff = 19.5 / 1000;
    var tempinc = (vOut - vZero) / tCoeff;
    var tempinf = tempinc * (9 / 5) + 32;
    console.log("Temp in C: " + tempinc);
    console.log("Temp in F: " + tempinf);
    //console.log(E.sum(view)/(view.length*65536));    
  } else first = false;
  // start it again
  w.startInput(A0,2000 /* Samples per second */);
}, 200);