DHT22/AM2302 temperature and humidity sensor

Just a quick note to say that if anyone else has trouble getting an AM2302 to work with the DHT22 library (getting -1 returned most of the time), try changing the timeout on this.to50ms to a higher number. 150ms works for the module I have and now it returns a correct value almost all the time.

I found through lots of debugging that the signal was getting cut off most of the time at about the 33rd/34th bit, which meant the checksum rarely matched. I would make some changes to the library, but I don't know if this is just my module that isn't working how it should or if it's common for all of them.

Thanks! Someone's actually had a go at a better module, which is here - I didn't want to have two conflicting ones, but hopefully at some point I'll merge that one into the normal DHT22 module.

You should be able to require("https://github.com/CanyonCasa/E­spruinoDocs/blob/master/devices/HTxx.js"­) and try the new one out though.

I only have a DHT11 to test with, but perhaps if I post a tweaked version of the original up you have have a test with that?

I found through lots of debugging that the signal was getting cut off most of the time at about the 33rd/34th bit, which meant the checksum rarely matched. I would make some changes to the library, but I don't know if this is just my module that isn't working how it should or if it's common for all of them.

I have seen issues where it gave out after 33/34 bits, but that was on a board that had only 32-level event queue, and when @Gordon increased it, the behavior changed.

I never encountered that issue when I was writing the DHT22 module code (also, 50ms or 150ms shouldn't matter - either of those are much longer than the signal takes to transmit. (that code is my fault, though @Gordon was an accessory)

If there are issues, it would be great if we could figure out how to fix the existing DHT22 module to work with them?

I'm not quite sure what the new HTxx module is trying to fix, hence not merging it in right away. It's definitely a bonus if one module can do all the different types though.

These troubles could well be a side-effect of people using Espruino on an ESP8266 where the event queue might be smaller?

I'll start a new thread with some ideas for a common module that will hopefully be compatible with everything, and is a bit cleaner and faster.

Just to add, the new 'general purpose' module actually doesn't work on my DHT11, when the old one does :)

Post on new module: http://forum.espruino.com/conversations/­281522/

Last question i read data from this sensor AM2301
and see ( Temp is -1 and RH is -1 )

All connected to GPIO D1.

Code from examples: dht.read(function (a) {console.log("Temp is "+a.temp.toString()+" and RH is "+a.rh.toString());});

My example programm:

var wifi = require("Wifi");
var dht = require("DHT22").connect(D1);

wifi.connect("xxx", {password:"xxx"}, function(err){
console.log("connected? err=", err, "info=", wifi.getIP());
});
wifi.stopAP();

wifi.save();

function readTemp(){
dht.read(function (a) {console.log("Temp is "+a.temp.toString()+" and RH is "+a.rh.toString());});
}

Thanks all .. this is my problem... i connect in my board D1 and Read from programm. D1.. But realy all pinout is other..

Example: ESPRUINO => D0 is my board => D3 -- GPIO0

2 Attachments

As that's not one of the Espruino boards, maybe try posting on the ESP8266 section of the forum? I believe some of the folks on there may have encountered some issues with ESP8266 and these sensors before.