nodemcu-firmware/docs/modules/dht.md

DHT Module

Since	Origin / Contributor	Maintainer	Source
2015-06-17	RobTillaart	Vowstar	dhtlib

Constants

Constants for various functions.

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

dht.read()

Reads all kinds of DHT sensors, including DHT11, 21, 22, 33, 44 humidity temperature combo sensor. Returns correct readout except for DHT12 and negative temperatures by DHT11. Use dht.read12() and dht.read11() instead. It is to use model specific read function anyway.

Syntax

dht.read(pin)

Parameters

pin pin number of DHT sensor (can't be 0), type is number

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 = 5
status, temp, humi, temp_dec, humi_dec = dht.read(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

dht.read11()

Read DHT11 humidity temperature combo sensor.

Syntax

dht.read11(pin)

Parameters

pin pin number of DHT11 sensor (can't be 0), type is number

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`.

See also

dht.read()

dht.read12()

Read DHT12 humidity temperature combo sensor.

Syntax

dht.read12(pin)

Parameters

pin pin number of DHT12 sensor (can't be 0), type is number

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`.

See also

dht.read()

dht.readxx()

Read all kinds of DHT sensors, except DHT11 and DHT12. Differs from dht.read() only by waiting only sufficient 1 ms for sensor wake-up while dht.read() waits universal 18 ms.

####Syntax dht.readxx(pin)

Parameters

pin pin number of DHT sensor (can't be 0), type is number

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`.

See also

dht.read()