I2C Bus Number Changed Unexpectedly on Jetson Orin Nano

Robotics & Edge Computing Jetson & Embedded Systems Jetson Orin Nano
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1

Hello,

I’m using a Jetson Orin Nano Developer Kit with JetPack 6.2 (L4T 36.4.3) and have encountered an unexpected issue with the I²C bus numbering.

🛠️ Issue Description

According to 'Jetson Orin Nano Developer Kit Carrier Board Specification’ , pins 3 and 5 (I2C1_SDA & I2C1_SCL) on the 40pins expansion header should be assigned to /dev/i2c-1 while pin 27 and 28 should be assigned to i2c-0.

However, after a fresh JetPack installation, these pins are now assigned to /dev/i2c-7 instead of /dev/i2c-1 while pin 27 and 28 is assigned to i2c-1.

I have confirmed this by running ls /dev/i2c-* and i2cdetect -y 7, which detects my connected device correctly.

🧪 Steps Taken to Troubleshoot

  1. Flashed JetPack 6.2 using SDK Manager (Clean installation)

  2. Checked device tree mappings (/proc/device-tree/aliases/i2c*) → /dev/i2c-7 is mapped to c250000.i2c, while /dev/i2c-1 is mapped to c240000.i2c.

  3. Verified I²C pinmux settings (/sys/kernel/debug/pinctrl/.../pinmux-pins | grep -i i2c) → No issues detected.

  4. Performed “Reset Settings in NVIDIA Configuration” in UEFI** → No change in behavior.

❓ Questions

  1. Has NVIDIA officially changed the I²C bus numbering in JetPack 6.2?
  2. If not, what could be causing this remapping?
  3. Is there a way to restore the default I²C bus mapping (/dev/i2c-1 for pins 3,5) without manually altering the device tree?

This behavior is unexpected, and I haven’t found any relevant discussions regarding this issue.
If this is an intentional change in JetPack 6.2, I would appreciate any official confirmation or documentation regarding this update.

Thanks in advance for your help!

3

Which release do you compare to?
Maybe you compare to Nano.

1 Like
4

I’m testing I2C on the expansion header on Jetson Orin Nano.
Until a few days ago, I2C pins 3 and 5 responded on bus number 1. Then suddenly, a few days ago, there was no response on bus 1.
In confusion, I looked into it and found that the bus number of pins 3 and 5 had changed to 7, and the bus number of I2C pins 27 and 28 had changed from 0 to 1.

So what I’m wondering is:

  • Why did the I2C bus number for those pins suddenly change?
  • And is it possible that the I2C bus number for those pins will change again?
5

Suppose the bus number is 7 from the begging.

6

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