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DHT20 / SHT20 notes

How can Rpi4B use python to talk to the I2C DHT20 / SHT20 temperature and humidity sensor?

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I’m trying to use a Raspberry Pi 4 to read an I2C temperature and humidity sensor. The part I’m using is a module from Grove based on the DHT20 sensor. Here’s a link to a page about the module:

https://www.seeedstudio.com/Grove-Temperature-Humidity-Sensor-V2-0-DHT20-p-4967.html

I need some help programming the I2C communication. The specs sheet for the sensor explains the frames that are needed for correct communication (see page 8):

I would be grateful if someone could show me the Python code needed to get a sensor reading. Preferably this would be based on the smbus package, but I will be grateful for any solution (based on whatever package you prefer). I understand that there are many answers about the DHT11 and DHT22 sensors, but these older models have one-wire logic whereas the newer DHT20 has I2C.

Thanks!pi-4i2csensortemperatureShareEditFollowClose 3Flagedited 1 hour agotlfong013,98733 gold badges88 silver badges2222 bronze badgesasked 2 days agothatguyfromcanada1333 bronze badges New contributor

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First start by finding the I2C address of your sensor. Here’s an explanation of how to do that: https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c (look under the section “Testing I2C”).

Once you have the address, try the following Python code:

import time
import smbus

address = 0x38 #Put your device's address here

i2cbus = smbus.SMBus(1)
time.sleep(0.5)

data = i2cbus.read_i2c_block_data(address,0x71,1)
if (data[0] | 0x08) == 0:
  print('Initialization error')

i2cbus.write_i2c_block_data(address,0xac,[0x33,0x00])
time.sleep(0.1)

data = i2cbus.read_i2c_block_data(address,0x71,7)

Traw = ((data[3] & 0xf) << 16) + (data[4] << 8) + data[5]
temperature = 200*float(Traw)/2**20 - 50

Hraw = ((data[3] & 0xf0) >> 4) + (data[1] << 12) + (data[2] << 4)
humidity = 100*float(Hraw)/2**20

print(temperature)
print(humidity)

ShareEditFollowFlaganswered 19 hours agoultracold2611 bronze badge New contributor

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