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With the BCM2711, there are two native I2C BUS:

  • I2C0 (GPIO0, GPIO1)
  • I2C1 (GPIO2, GPIO3)

However you can have alternate I2C bus according from §5.3 on the bcm2711-peripherals-pdf. For instance, we can have:

  • I2C4 (GPIO6, GPIO7)

My question is:

Are the two main I2C buses faster than the other alternate functions?

nowox
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2 Answers2

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All the 8 hardware I2C buses on the Pi 4 are identical.

The Broadcom Serial Control (BSC) controller is a master, fast-mode (400Kb/s) BSC controller. The Broadcom Serial Control bus is a proprietary bus compliant with the Philips® I2C bus/interface version 2.1 January 2000.

joan
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Chapter 3 of the available documentation states that all of the hardware-based I2C buses on the BCM2711 (RPi 4) operate under the control of the Broadcom Serial Controller, or BSC. The RPi hardware and firmware are closed-source, but relying on the documentation, a reasonable assumption is: "No - none of the hardware-based I2C channels are faster than the others."

Just to be clear, I use the phrase "hardware-based" to designate I2C buses sourced by the BSC, and to distinguish from the "software-based" I2C buses. I've not tried a "software-based" I2C bus, but I've read they are not able to operate at the same speeds as a "hardware-based" I2C.

Both hardware and software I2C buses may be configured as overlays in /boot/config.txt. For details see your RPi's local filesystem at /boot/overlays/README, or at The Foundation's GitHub site.

Finally, there is a similar question, and answers that may be of interest to you.

Seamus
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