nodemcu-firmware/docs/modules/dht.md

DHT Module

Since	Origin / Contributor	Maintainer	Source
2017-03-30	Arnim Läuger	Arnim Läuger	dht

Constants

Constants for various functions.

dht.OK, dht.ERROR_CHECKSUM, dht.ERROR_TIMEOUT represent the potential values for the DHT read status

dht.read11()

Read DHT11 humidity temperature combo sensor.

Syntax

dht.read11(pin)

Parameters

pin IO index, see GPIO Overview

Returns

• status as defined in Constants
• temp temperature
• humi humidity
• temp_dec temperature decimal (always 0)
• humi_dec humidity decimal (always 0)

Example

pin = 4
status, temp, humi = dht.read11(pin)
if status == dht.OK then
    print("DHT Temperature:"..temp..";".."Humidity:"..humi)

elseif status == dht.ERROR_CHECKSUM then
    print( "DHT Checksum error." )
elseif status == dht.ERROR_TIMEOUT then
    print( "DHT timed out." )
end

dht.read2x()

Read DHT21/22/33/43 and AM2301/2302/2303 humidity temperature combo sensors.

Syntax

dht.read2x(pin)

Parameters

pin IO index, see GPIO Overview

Returns

• status as defined in Constants
• temp temperature (see note below)
• humi humidity (see note below)
• temp_dec temperature decimal
• humi_dec humidity decimal

!!! note

If using float firmware then `temp` and `humi` are floating point numbers. On an integer firmware, the final values have to be concatenated from `temp` and `temp_dec` / `humi` and `hum_dec`.

Example

pin = 4
status, temp, humi, temp_dec, humi_dec = dht.read2x(pin)
if status == dht.OK then
    -- Integer firmware using this example
    print(string.format("DHT Temperature:%d.%03d;Humidity:%d.%03d\r\n",
          math.floor(temp),
          temp_dec,
          math.floor(humi),
          humi_dec
    ))

    -- Float firmware using this example
    print("DHT Temperature:"..temp..";".."Humidity:"..humi)

elseif status == dht.ERROR_CHECKSUM then
    print( "DHT Checksum error." )
elseif status == dht.ERROR_TIMEOUT then
    print( "DHT timed out." )
end