Camera i2c speed issues for Jetson NANO


I tried to use one camera via CSI on Jetson NANO and I found it was not stable because there are sometimes some data missing during i2c communication.

First I found the problem is related to USB hub(RTS5411). I found that it was not stable via i2c if I didn’t connect any USB device. But If I connected one, it can work. It was a really unusual situation.

Then I check the default clock frequency of i2c was 400k for CAM_I2C and I found the USB hub and CSI used the same bus, like the below figure.

However, I found RTS5411 was connected via SMBus(SMBCL/SMBDA) not i2cbus(SCL/SDA) and the frequency of SMBus was just only supported to 100K. I didn’t know why using SMBus but i2c.

So I think that’s why the i2c data was sometimes missed when I used my cameras via I2C because there is a potential problem if the clock frequency is 400K. I should change it to 100K, and exactly it can work.

Although I hope to enable cameras via fast-speed i2c, it is the hardware limit so I think it cannot ensure the stability of i2c faster than 100k.

Sorry for the late response, is this still an issue to support? Thanks

Thanks for your response.
I already solved it and I can run correctly with 100K and I think that’s the only way.
I’m just confused why not use i2c but SMBus? Because it makes cam_i2c cannot set to 400k.
Maybe using imx219 is hard to find this issue, but this is a potential problem while reading a large amount of data via i2c.

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