Thanks so much for taking the time to respond.
I also cannot get an Arduino Uno to recognize the I2C address when I run the scanner program. I have been powering the sensor with an external power supply for all of these tests. Usually around 9 volts because that seems to be the number where people don't have any problems.
The sensors also have a DVCC pin (which I mentioned earlier) that is meant to be separate from the sensor power and is only associated with the logic of the I2C side of things... this is the only pin that I was powering by the Wemos in one test (and an Arduino in another test.)
I have tested 3 situations, all of which I supplied 9V to the sensor with an external power supply and had a common ground between everything.
1. providing 5V to DVCC via an Arduino
2. providing 3.3V to DVCC via an Arduino
3. providing 3.3V to DVCC via a WEMOS (ESP8266)
None of the scans found an I2C address.
As a side note, the sensor works fantastic if not using I2C, and instead, using a custom library/code found HERE
or another example seen below...
// Create K30 instance on pin 6 & 7
// Get CO2 value from sensor
double co2 = K_30.getCO2('p');
// Print the value on Serial
Serial.print("Co2 ppm = ");
// Wait 2 seconds
The problem, however, is that I can't get this code to compile on the WEMOS, only on the Arduino. I'm wondering if it has anything to do with SoftwareSerial not working the same on the ESP8266?
My project requires the ability to transmit this data wirelessly, therefore my workaround was going to be to have the Arduino take the measurements with the code that works, and then transfer those measurements via I2C to the WEMOS and let the WEMOS then throw this measurement over the airwaves. It's ridiculously tedious when the WEMOS itself should simply be able to read the value via I2C directly from the sensor and do all these things.
Once again, any help is greatly appreciated. I have to imagine someone has gotten this beauty up and running on I2C.
Thanks once again for looking into this as I'm crashing and burning fast right now...