DS18B20 Not Found

[espruino-discuss3]

Posted at 2022-01-25 by sammachin

Been doing some experiments with a DS18B20 sensor on an Espruino WiFi, I've had a couple of successful reads but mostly I'm getting this error:

(Sorry for the screenshot I can't figure out how to copy/paste from the console!

My code is just this for now:

var ow = new OneWire(A0);
var sensor = require("DS18B20").connect(ow);

function read(){
  sensor.getTemp(function (temp) {
    console.log("Temp is "+temp+"°C");
});
}

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Attachments:

• Screen Shot 2022-01-25 at 8.37.07 AM.png

[espruino-discuss3]

Posted at 2022-01-25 by @gfwilliams

Do you have a pullup resistor on A0? There could be some instability if not.

Also are you powering the DS18B20 on the 3rd pin, or trying to run it parasitically?

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Posted at 2022-01-25 by sammachin

Ah yes, pullup resistor that's sorted it, thanks :)

Are there internal pullups I can use in this scenario?

Sam

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Posted at 2022-01-25 by @gfwilliams

Yes and no... So as far as I remember the nRF52 can do it, but the ST parts had some strange behaviour where it was really hard to keep the pullup on something that was an output so I don't think they could...