I2C pull-up resistors on modules and breakout boards

I will use 5 different sensor for an air quality monitoring system.
If all the 5 module sensors have l2C pull-up resistors, the 5 resistors will be in parallel.

Could I lost communication? What should I do?

Ideally you’d only have one set of pull-ups on one bus. If all your modules have their own set, try deactivating/removing them from a few boards.
2k2 should be the lower limit of all pull-ups on one line. You may get away with lower values but this will put more strain on the devices to actually pull low and the logic level might not got low completely.

Some testing with all pull-ups in place shouldn’t hurt the devices tho.

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Most generally the I2C pull up jumpers are not necessary. The Photon will internally pull the SDA and SCL lines high. The only time pull up jumpers are necessary is if you have a very long cable run to the sensors. I would try without any of the jumpers installed to start.

Hmm, I don’t think this is the case tho’


I have had devices not respond if I forgot to put the resisters on .

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