Hi,
I need to connect two BME280 sensors to my Arduino Uno, one with 1m cable (Cat5) length and the other one with 5m. So, I read, I can't have them both on the same I2C pin because of the total cable length.
But could I put them on two seperate I2C pins? I also have a BH1750 and a DS3231 on my board on I2C. Can I fit all of that on one board?
Technically speaking you can't have either of your BME280 sensors on any combination of I2C pins due to cable length. This communication protocol is designed for devices that are all mounted on the same pc board.
That being said I have somewhat successfully used a BME280 on a 5m Cat5 cable but I would not describe the setup as being totally reliable. That setup also had a DS3231 on the same I2C bus.
I am in the process of revising things to run my 'remote' BME280 on an ESP8266 using the Cat5 cable to provide power.
Except for the distance problem I can see no reason why you can't run all four devices on the same I2C bus. Don't forget to change the I2C address on one of your BME280s. I would get the system working with all of your devices close to one another, then after things are functioning properly try adding the Cat5 cables, one at a time.
Don
Thanks for your reply!
floresta:
That being said I have somewhat successfully used a BME280 on a 5m Cat5 cable but I would not describe the setup as being totally reliable.
Does that mean, it could be whithout any signal at all or that the cable could influence the measuring value? Or both?
I'm only reading it once per minute, does that have anything to do with its reliability?
Does that mean, it could be whithout any signal at all or that the cable could influence the measuring value? Or both?
I'm only reading it once per minute, does that have anything to do with its reliability?
It might not return any value as the signal won't get correctly transferred to the sensor. This is caused by the higher capacitance of the cable and the idle state being produced by simple pull-ups. One way to get the edges steeper is to lower the resistor value but the quickly get over the current limit of the I2C standard (so you might fry the sensor).
phytopia:
Thanks for your reply!Does that mean, it could be whithout any signal at all or that the cable could influence the measuring value? Or both?
I'm only reading it once per minute, does that have anything to do with its reliability?
As I recall (it was a while ago) it just stopped working, I didn't get any values returned as pylon has guessed. I could typically jump start it by removing and replacing the power.
Don