DS18B20 Not Found

Posted on Tue 25th, January 2022

• #1

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");
});
}
```
1 Attachment
• #2

Gordon

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?
• #3

sammachin

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

Are there internal pullups I can use in this scenario?

Sam
• #4

Gordon

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...

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