My use-case is to have multiple sensors with the same I2C address attached to the PI and also a LED screen that I want to attach on it's own. I found that there is a software level overlay BUT it is super slow and I am looking to see if there is a way to activate any of the PI pins as I2C pins on the hardware layer.

Links and things already tried
[1] https://www.raspberrypi.org/forums/viewtopic.php?t=295392
[2] Pi Zero W: Second i2c Bus
[3] https://github.com/raspberrypi/firmware/blob/master/boot/overlays/README#L1409-L1455

1 Answer 1


The Pi Zero has two hardware I2C buses.

Bus 0 (/dev/i2c-0) uses GPIO 0/1. Bus 1 (/dev/i2c-1) uses GPIO 2/3.

You can probably use bus 0 as well as bus 1 on a Pi Zero.

An alternative to consider is an I2C bus multiplexor such as the TCA9548A which will allow you to have up to 8 devices sharing the same I2C address.

If the software I2C bus seems super slow that suggests you have unrealistic expectations or have done something wrong.

  • thank you for the suggestions, I will research the multiplexer approach. For the slowness, all I have done is issue an i2c scan. Scanning bus 0 is immediate, scanning a new bus using a software controller takes many minutes. I have not used pull-ups, perhaps that is the issue? Sep 18, 2021 at 17:53
  • bus1 is reserved, I tried using it but it's a complete pain the butt, and I either fried or broke the I2C controller on an LED screen trying to utilize that bus. Googling for it revealed many frustrations and solutions difficult. Sep 18, 2021 at 17:55

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