I am trying to measure humidity and temperature using the sonoff si7021 and an Arduino UNO but have so far been failing, so I'm wondering whether this is possible at all. The sonoff si7021 sensor is quite different from the "pure" si7021. Sonoff added a microcontroller but I cant seem to find information on what protocol it uses. This post suggests it might be compatible with DHT11/22 sensors:
There are some indicators on the Itead Wiki that this single wire bus is compatible with DHT11/22 sensors. So try to read the sensor using that protocol but you won't be successful if you request data as if it was a directly connected SI7021.
I have a functioning setup with a DHT11 on my breadboard but when I replace the DHT11 with the sonoff sensor, I get no readings.
At the same time, I realized that the sonoff sensor takes a maximum of 3.6v and I have been testing it with 5V :-/ so I'm not sure if it is still intact. Is there a simple way of checking? (There is no visible damage on the sensor board).
When I realized my mistake, I used the 3.3 V pin on the UNO, but I'm not even sure whether that pin can be used in that way (I know it can be used as reference voltage, but as supply voltage? As you will have guessed, I'm quite a beginner in the Arduino world...)
So, since I'm having so many uncertainties that make it difficult to continue, I'm posting here, hoping you might be able to help me eliminate some of those unknowns.