Timeouts reading from sensor

[brlnr23]

I have searched a lot in this repository but unfortunately I couldn't find a solution for the problem I am facing.

I constantly get an error reading data from the sensor: Error: failed to read sensor

First off

1. Using the Adafruit example script returns the values I am expecting - so it seems that its not a wiring issue
2. I am using a DHT22 sensor (as module) without a pull up resistor
3. Raspberry Model B V2.0 / npm -v: 6.14.8 / node -v: v9.11.1
4. I have installed the package with the verbose flag npm install node-dht-sensor --dht_verbose=true

If I run that simple script (taken from the examples) it returns an error. The logfile just says

start sensor read (type=22, pin=14).
*** timeout #2

sensor = require("node-dht-sensor");
var usage =
  "USAGE: node async-explicit.js [sensorType] [gpioPin] <repeats>\n" +
  "    sensorType:\n" +
  "         11: For DHT11 sensor.\n" +
  "         22: For DHT22 or AM2302 sensors.\n\n" +
  "    gpipPin:\n" +
  "         Pin number where the sensor is physically connected to.\n\n" +
  "    repeats:\n" +
  "         How many times the read operation will be performed, default: 10\n";

if (process.argv.length < 4) {
  console.warn(usage);
  process.exit(1);
}

var sensorType = parseInt(process.argv[2], 10);
var gpioPin = parseInt(process.argv[3], 10);
var repeats = parseInt(process.argv[4] || "10", 10);
var count = 0;
var start = 0;
var end = 0;

var iid = setInterval(function() {
  if (++count >= repeats) {
    clearInterval(iid);
  }

  start = new Date().getTime();

  sensor.read(sensorType, gpioPin, function(err, temperature, humidity) {
    end = new Date().getTime();
    if (err) {
      console.warn("" + err);
    } else {
      console.log(
        "temperature: %s°C, humidity: %s%%, time: %dms",
        temperature.toFixed(1),
        humidity.toFixed(1),
        end - start
      );
    }
  });
}, 3000);

Results in:

node index.js 22 14 1
(node:5316) Warning: N-API is an experimental feature and could change at any time.
BCM2835 initialized.
Error: failed to read sensor

If I run the same script but with type 11 it returns completely wrong values, but it returns at least something

node index.js 11 14 1
(node:5326) Warning: N-API is an experimental feature and could change at any time.
BCM2835 initialized.
temperature = 0, humidity = 2
temperature: 0.0°C, humidity: 2.0%, time: 52ms

To me this looks like an issue with the DHT22 type of sensor. Any hints are welcome. I am happy to provide more information if needed

[cainpsycode]

Hello! I also had the same error and found a solution for myself. I found a difference between the dht-sensor implementation and the protocol, in particular the low trigger value timeout it should be within 1-18ms. I have increased the low voltage latency from 800ms to 1000ms.
changes:
cainpsycode@50811e3

[oscar-c]

Hello! I also had the same error and found a solution for myself. I found a difference between the dht-sensor implementation and the protocol, in particular the low trigger value timeout it should be within 1-18ms. I have increased the low voltage latency from 800ms to 1000ms.
changes:
cainpsycode@50811e3

I too had this problem. The mentioned changes fixed my problem as well.

[brlnr23]

thanks for this hint. Since I am no c++ guy at all: am I right that I need to complile the cpp files? And if so: do you have any hints how a bloody starter is able to do so ;)

[cainpsycode]

thanks for this hint. Since I am no c++ guy at all: am I right that I need to complile the cpp files? And if so: do you have any hints how a bloody starter is able to do so ;)

Yes you need rebuild native cpp code for your target platform. Just follow the instruction https://github.com/momenso/node-dht-sensor#reference-for-building-from-source

[brlnr23]

a big up to you, @cainpsycode! After some back and forth it worked for me!

If someone else wants to build it from source:
I did that on my Raspberry directly. For me, there was to need to run the following command

$ sudo update-alternatives --install /usr/bin/node-gyp node-gyp /opt/node-v10.15.3-linux-armv7l/bin/node-gyp 1

Instead I need to run the following commands as sudo in the node-dht-sensor directory

$ sudo node-gyp configure
$ sudo node-gyp build

I was also missing the package node-addon-api but a simple npm install node-addon-api fixed it.

Once the build process has been completed I could import the self-made build via - in my case with promises -

var sensor = require("./lib").promises;

... do fancy things here

// edit: no I hope that the library does not suffer from the negativ values bug as the Python lib I used to use does ;)

[cainpsycode]

a big up to you, @cainpsycode! After some back and forth it worked for me!

If someone else wants to build it from source:
I did that on my Raspberry directly. For me, there was to need to run the following command

$ sudo update-alternatives --install /usr/bin/node-gyp node-gyp /opt/node-v10.15.3-linux-armv7l/bin/node-gyp 1

Instead I need to run the following commands as sudo in the node-dht-sensor directory

$ sudo node-gyp configure
$ sudo node-gyp build

I was also missing the package node-addon-api but a simple npm install node-addon-api fixed it.

Once the build process has been completed I could import the self-made build via - in my case with promises -

var sensor = require("./lib").promises;

... do fancy things here

// edit: no I hope that the library does not suffer from the negativ values bug as the Python lib I used to use does ;)

There is no hope. The negative values are wrong.

I fixed it, but I can't be sure if the solution is correct.
@brlnr23 you can try this branch https://github.com/cainpsycode/node-dht-sensor/tree/bugfix/tmp-negative

[JulianWowra]

I have the same timeout problem when I run the DHT11 sensor on 3.3V. I have changed my setup and use 5V on the sensor. But even there it happens sometimes!

I hope this problem will be solved soon in the LIB

[Ricky1966]

Hi, sorry for my english, but isn't my first languege.
I've read this discussion, I've try to change latency as @cainpsycode suggest, I've compiled and try, the issue there is still.
Also I, with Python, have the rigth values, so isn't a probe problem.
I've changed voltage to 3v3. Yet same problem.
Someone have fixed this problem?
Ther is a fork of project?
Tks