thanks a lot. About setting more than just one I²C-device, I was already aware, but you already gave me a lot of ideas I want to check first. 

I think you already shown me the way to go on.

@byron: Enjoy your beer.

@Inq, there are also interesting ideas coming from you. 

Thanks again, have a nice weekend, 

Greetings from Germany

Wolfgang

@zander your slowing down and this time my post came first, I feel one of my legs must be getting shorter.

Don't I feel like the tortoise!  Just wait till I get fiber at the house and I'll be in the running.  😎   

Posted by: @wolfgangw

So far I've only found examples online that connect the CS of the monitor to a D2 connection of the various ESPxxx. Now the SDA is there too. In the examples there, however, only the use of ESPxxx and the monitor is described, not the use of additional sensors that use this I²C interface.

@wolfgngw is there something special about the I2C as it applies to this monitor?  Does it have both the SCL and SDA lines?  On the ESP8266 (NodeMCU or Wemos) these go to D1 and D2 respectively.  Those are the default lines for I2C and libraries for sensors assume these. 

As Ron and Bryon said, you can have as many I2C devices on that "bus" (D1,D2) as long as they have different addresses.  It is just like a network with IP addresses.  In my current project https://forum.dronebotworkshop.com/user-robot-projects/inqling-junior-robot-mapping-vision-autonomy/, I have five sensors on the same, default I2C bus D1,D2.  Accelerometer, Gyro, Magnetometer, Barometer and ToF sensor.

There is one situation that can arise from having too many sensors on the same bus.  Most sensors include pull-up resistors built-in.  If too many sensor have these, the pull up will be too strong and the network will fail.  I've only read this as my situation above does not have this problem.  Probably because four of those sensors are on one board and they only have the one set of pull ups for all four.  

If however any two sensors have the same address, you can always create a second I2C bus out of any other pins, say... D3, D4.  I've done this before, and if you have this situation, let me know and I'll see what was done for that.

Either way, you can just wire them up to your ESP and using the I2C scanner sketch ...

https://github.com/todbot/arduino-i2c-scanner/blob/master/I2CScanner/I2CScanner.ino

... it will scan all your pins and tell you which one have an I2C device connected and what its address is.  

VBR,

Inq

I think my UNO is a clone and has 3.3V as well as 5V outputs.

Mine have a 3.3v and 5v power pins, but the digital I/O pins are all 5v when driven high.

When doing a quick ad hoc experiment, I almost always use a UNO

and then fry your nice 3.3v sensor...  Well thats what I did,  I think I will ditch my arduio boards they just gather dust now.

When doing a quick ad hoc experiment, I almost always use a UNO if it will work since it's mounted with a breadboard etc.

@byron Oops

😀, but that picture you show is of a venerable arduino uno.  Did you raid the museum.  You should really dig out one of your ESP32 S3 boards or even a shiny new rpi pic W board.  

Well I'm drinking my beer, but why put off the i2c pin stuff until tomorrow, so I refer you to a random nerd post and note that somewhere he refers to using different i2c pins to the default ones.

https://randomnerdtutorials.com/esp32-i2c-communication-arduino-ide/