can i read i2c Voltage like read analog voltage?
I2C is a physical communication method between processors and peripherals. It runs at 5V, or 3V, depending on the processor and the peripherals design. There's nothing to 'read' voltage wise.
If you're asking if you can read an analog voltage using an I2C peripheral, of course you can. Tell us more about your application, and I'm sure someone will recommend a suitable ADC, presuming one is required.
So, tell us more about your application. Maybe this will help:
hello camsysca,
I need the voltage data from the bme280 that I use, so I can find out how many volts are being used at a certain temperature so that it can be entered into the jobsheet table
Well, start here:
Please, post a picture of the BME280 Breakout Board you are using and the type of your Arduino.
You can read the I2C voltage, the best way is to hold the reset button when you do, that keeps it from communicating. When it is communicating it will have a square wave signal that will not translate to volts but is very readable to a scope or logic analyzer. The volts being used is not perterent, it wants a given amount to work. It communicates the data back to the processor when it asks via the I2C bus.
I will take a SWAG and assume you are new to the electronics and computer world. I highly recommend you get a copy of the Arduino Cookbook any version and skim it cover to cover then read the sections perterenate to your project. While you are waiting on that follow some tutorials on basic electronics especially Ohm's law. This will be a big boost as to what is happening on your project. We have all been there and out goal here is to help you help yourself.
To be clear, I pointed you at the Adafruit sensor page because that page also has descriptive info, a tutorial, and links to Arduino software. So it's a really good starting place; I was not 'shilling for Adafruit' to get you to buy their product, though that would be an option as they're a great presence in the Arduino world for beginners.
The i2c voltage of the bme280 has nothing to do with temperature data
Without a good project/problem description, I'll take a leap on this, and presume that what you're trying to say is, you want to see if there's a voltage-temperature correlation, and hence you're reading a voltage using the BME device. But, where are you getting your temperature data from? Are you storing data somewhere?
@camsysca
It seems to me that OP thinks, that the I2C bus transmits data as an analog signal proportional to the temperature.
You read it one way, I read it another(post #3), and it really doesn't matter until we get an intelligible problem description. So I'll just walk away until we see one.
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Are you asking for the voltage (that varies with temperature) at the indicated point of the following diagram (Fig-1)?
It is possible by opening the cpp file, looking for the readTemperature method of the attached Library, find the equation for Temperature and do the back calculation.
Adafruit_BME280_Library-master.zip (447.0 KB)
Figure-1:
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BME can be BioMedical Engineering at the New Jersey Institute of Technology. If I only could find course number 280 
Is number 680 close enough ? It is about MEMS sensors: Course Syllabi | Department of Biomedical Engineering
BME may stand for: Barometer and Environmental Sensor.
i'm using this bme280
yes i need a correlation from voltage - temperature like this
@setricka, is this a school assignment?
There is no way to get such correlation with bme 280.
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And which Arduino -- UNO, NANO, MEGA?
And which Arduino -- UNO, NANO, MEGA?
How would that change the use of I2C to communicate with a BME sensor?
In answer to your question you can read the analog voltage but it only will tell you the power is on or off depending on your reference point. The definitive answer is in the data sheet. I suggest you take the time to read it and understand what you are reading. Then follow some tutorials on I2C. But first study the difference between analog and digital.