Using DS18B20/DTH11 with GPIO0 and GPIO2?

[Elektrofreak]

Hi all,

I am currently setting up a new PCB for heating automatisation using the ESP8266 with ESPEasy and FHEM and i am running out of IOs for the ESP12-E board.

I was questioning myself if it would be safe to connect the DS18B20 one wire temperature sensor and the DTH11/DTH22 humidity sensors to the GPIO0 and GPIO2 pins. The data line has a pull up by default so it should not be a big problem as long as the sensors don't do any strange thing during startup.

I think the DS18B20 should be safe because it will be supplied from the 3.3V of the ESP8266.

Especially for the DTH11, it could be a tricky thing because it would like to have a 5V supply. It also works with 3.3V but some sources say that it reduces accuricy for <3.6V. Thus i would like to supply it from something between 3.6V and 5V which would have low impact on connecting it to the 3.3V ESP8266. Main issue could be the startup procedure depending on how the DTH11 protects the data pin against overvoltage (diode to vdd?). In case of low supply voltage of the DTH11, it could pull down the GPIO0/GPIO2 and disturb the startup of the ESP.

Do you have any recomendations concerning this?